To see the other types of publications on this topic, follow the link: Rice pests.
Dissertations / Theses on the topic 'Rice pests'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Rice pests.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Nugaliyadde, Lionel. "Factors associated with the resistance of rice (Oryza sativa L.) to Nilaparvata lugens (StaÌŠl)." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387408.
Full text
2
Chiasson, Hélène. "Determination of key factors affecting the population dynamics of Diopsis longicornis and D. apicalis (Diptera:Diopsidae), pests of rice in the Republic of Guinée, West Africa." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74604.
Full textAbstract:
Pest status of the rice stem-borers, Diopsis longicornis and D. apicalis was not well known in the Republic of Guinee.<br>In the present study, adult and immature populations of both species were monitored under various local cultural practices, i.e., planting methods (direct and transplanted), different planting dates and seasons (wet and dry). As previously observed in other West African countries, D. apicalis did occasional damage to rice in Guinee. However, contrary to findings elsewhere, D. longicornis was not an important pest of Guinean rice, infesting 4% of stems over the five seasons studied.<br>Regulators affecting population size and behaviour of D. longicornis were determined, focusing on factors controlling the fly's quiescent period in aggregation sites during the dry season, and the insect's movement to and from these refugia. Availability of cultivated and wild rice was found to interrupt or prevent quiescence of D. longicornis. Abiotic factors, (relative humidity, rainfall and photoperiod) influenced time of dispersal of D. longicornis.
3
Preap, Visarto. "Localised outbreaks of brown planthopper (Nilaparvata lugens Stål) in Cambodian rice ecosystems : possible contributing factors /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18971.pdf.
Full text
4
Singh, Satya Ram, University of Western Sydney, of Science Technology and Agriculture Faculty, and School of Horticulture. "Biology of the rice leafroller Cnaphalocrocis (Marasmia) exigua (Butler) (Lepidoptera: Pyralidae: Pauristinae) in Fiji." THESIS_FTA_HOR_SINGH_S.xml, 1997. http://handle.uws.edu.au:8081/1959.7/443.
Full textAbstract:
The rice leafroller Cnaphalocrocis exigua (Butler) in the only species of the rice leaf folder/roller complex in Fiji. It is one of the major rice pests in the country, its pest status being exacerbrated by the cultivation of high-yielding varieties with minimal pest resistance. Detailed studies on the biology of the moth, in particular on the development, emergence, mating and flight behaviour, effect of adult nutrition on fecundity, egg hatchability and longevity, effect of larval nutrition on larval survival, pupation, pupal weight, pupal eclosion, and fecundity, egg hatchability and longevity of resultant adults, parasitism, and population ecology of C. exigua were carried out in Fiji from 1985 to 1987, and from June to August 1990. This study showed that there are several parasitoids of C. exigua in Fiji, and of those the egg and larval parasitoids Trichogramma sp. and Trathala flavo-orbitalis (Cameron) respectively are significant biotic mortality factors. Their impact as natural suppressors of C. exigua in fields of high yielding rice varieties was, however, inadequate to prevent C. exigua reaching damaging levels. Since C. exigua responds strongly to rice varietal differences, plant nitrogen status, and seasonal factors, is suspected to utilise pheromones during mating, and has numerous biocontrol agents in South East Asia and the Philippines, it appears to be an excellent candidate for an integrated pest management (IPM) program in Fiji. Before IPM strategies can be formulated, however, further investigations on rice varietal resistance, exploitation of exotic parasitoids and pathogens, and detailed studies on the possible presence of sex pheromones need to be conducted.<br>Doctor of Philosophy (PhD)
5
Afun, Jakpasu Victor Kofi. "The role of weeds in the natural control of upland rice insect pests in Cote d'Ivoire, West Africa." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268021.
Full text
6
Singh, Satya Ram. "Biology of the rice leafroller Cnaphalocrocis (Marasmia) exigua (Butler) (Lepidoptera: Pyralidae: Pauristinae) in Fiji." Thesis, Richmond, N.S.W. : School of Horticulture, Faculty of Science, Technology and Agriculture, University of Western Sydney, Hawkesbury, 1997. http://handle.uws.edu.au:8081/1959.7/443.
Full textAbstract:
The rice leafroller Cnaphalocrocis exigua (Butler) in the only species of the rice leaf folder/roller complex in Fiji. It is one of the major rice pests in the country, its pest status being exacerbrated by the cultivation of high-yielding varieties with minimal pest resistance. Detailed studies on the biology of the moth, in particular on the development, emergence, mating and flight behaviour, effect of adult nutrition on fecundity, egg hatchability and longevity, effect of larval nutrition on larval survival, pupation, pupal weight, pupal eclosion, and fecundity, egg hatchability and longevity of resultant adults, parasitism, and population ecology of C. exigua were carried out in Fiji from 1985 to 1987, and from June to August 1990. This study showed that there are several parasitoids of C. exigua in Fiji, and of those the egg and larval parasitoids Trichogramma sp. and Trathala flavo-orbitalis (Cameron) respectively are significant biotic mortality factors. Their impact as natural suppressors of C. exigua in fields of high yielding rice varieties was, however, inadequate to prevent C. exigua reaching damaging levels. Since C. exigua responds strongly to rice varietal differences, plant nitrogen status, and seasonal factors, is suspected to utilise pheromones during mating, and has numerous biocontrol agents in South East Asia and the Philippines, it appears to be an excellent candidate for an integrated pest management (IPM) program in Fiji. Before IPM strategies can be formulated, however, further investigations on rice varietal resistance, exploitation of exotic parasitoids and pathogens, and detailed studies on the possible presence of sex pheromones need to be conducted.
7
Truong, Xuan Viet. "Optimization by Simulation of an Environmental Surveillance Network : application to the Fight against Rice Pests in the Mekong Delta (Vietnam)." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066278/document.
Full textAbstract:
Un réseau de surveillance efficace est souvent un outil utile pour surveiller et évaluer les différents états d'un écosystème spécifique. Avec les informations fournies par le réseau, les prédictions peuvent être générés en utilisant des analyses spatio-temporelles approfondies, qui peuvent ensuite aider les décideurs et les parties prenantes. Écosystèmes dominés par les humains sont très dynamique et complexe, où la plupart des variables observées ont des interactions non-linéaires mutuelles. En outre, les impacts des activités humaines sur l'écosystème sont souvent rugueux, dans de nombreux cas, ils perturbent l'équilibre écologique. Par conséquent, la surveillance d'un écosystème devient un problème complexe et il n'est pas facile de proposer un réseau de surveillance optimal en utilisant les techniques traditionnelles. Les techniques d'optimisation traditionnelles ne parviennent pas souvent à tenir compte des évolutions de la réalité associée à ces écosystèmes.Un exemple d'une telle situation se trouve à la région du delta du Mékong du Vietnam, où les gestionnaires provinciaux de l'agriculture sont concernés par les invasions régulières des cicadelles brunes (Brown Plant Hoppers - BPH), un ravageur du riz particulièrement active, à cause des maladies qu'ils véhiculent et transmettent à la les rendements de riz<br>An efficient surveillance network is an invaluable tool to monitor and assess the different states of a given ecosystem. With the information collected by such a network, predictions can be generated using thorough spatio-temporal analyses, which can then support decision makers and stakeholders. Human dominated ecosystems are highly dynamic and complex , where most of the observed variables have mutual non-linear interactions. In addition, the human activities have a considerable impact on almost all ecosystems they inhabit, where they tend to disrupt the ecological balance in short period of times. The surveillance of such ecosystems by different technical solutions is complex and dynamic where designing an “optimal” surveillance network, i.e., a network that would reflect an almost realtime situation of an ecosystem. Often traditional optimization techniques fail to reflect the evolutions of the reality associated with these ecosystems.An example of such a situation, is the Mekong Delta region of Vietnam, where the provincial agricultural managers are concerned with the regular invasions of Brown Plant Hoppers (BPH), a particularly active rice pest, because of the diseases they carry and transmit to the rice yields. Their biggest concern is having a constantly accurate account of the current distribution of BPH waves, since it is the basis of establishing different prevention strategies. The time frame is short for applying these strategies: at least one week is needed between the moment where a prediction of the density of BPH can be estimated by the experts and warnings are sent to farmers and other end users and the moment where a strategy can be efficiently applied. To improve the efficiency of the system, the Vietnamese government has established a light-trap network [1] [2] that can capture multiple kinds of insects, especially BPH, and which data (the density of insects per trap) is collected and analyzed daily. Maintaining this network in a good state of operation has become an important national program of the Ministry of Agriculture and Rural Development of Vietnam since 2006. Although the current light-trap network is considered as a necessity for supporting the fight against various plant pests, it has three restrictions: (1) it misses detailed accounts on the life cycle of the BPH, (2) the network has remained stable since its initial design and has not, therefore, completely adapted to the huge changes that the ecosystem of the Mekong Delta has undergone in the recent years especially due to limitations in management, and (3) the network itself is very sparsely distributed
8
Truong, Xuan Viet. "Optimization by Simulation of an Environmental Surveillance Network : application to the Fight against Rice Pests in the Mekong Delta (Vietnam)." Electronic Thesis or Diss., Paris 6, 2014. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2014PA066278.pdf.
Full textAbstract:
Un réseau de surveillance efficace est souvent un outil utile pour surveiller et évaluer les différents états d'un écosystème spécifique. Avec les informations fournies par le réseau, les prédictions peuvent être générés en utilisant des analyses spatio-temporelles approfondies, qui peuvent ensuite aider les décideurs et les parties prenantes. Écosystèmes dominés par les humains sont très dynamique et complexe, où la plupart des variables observées ont des interactions non-linéaires mutuelles. En outre, les impacts des activités humaines sur l'écosystème sont souvent rugueux, dans de nombreux cas, ils perturbent l'équilibre écologique. Par conséquent, la surveillance d'un écosystème devient un problème complexe et il n'est pas facile de proposer un réseau de surveillance optimal en utilisant les techniques traditionnelles. Les techniques d'optimisation traditionnelles ne parviennent pas souvent à tenir compte des évolutions de la réalité associée à ces écosystèmes.Un exemple d'une telle situation se trouve à la région du delta du Mékong du Vietnam, où les gestionnaires provinciaux de l'agriculture sont concernés par les invasions régulières des cicadelles brunes (Brown Plant Hoppers - BPH), un ravageur du riz particulièrement active, à cause des maladies qu'ils véhiculent et transmettent à la les rendements de riz<br>An efficient surveillance network is an invaluable tool to monitor and assess the different states of a given ecosystem. With the information collected by such a network, predictions can be generated using thorough spatio-temporal analyses, which can then support decision makers and stakeholders. Human dominated ecosystems are highly dynamic and complex , where most of the observed variables have mutual non-linear interactions. In addition, the human activities have a considerable impact on almost all ecosystems they inhabit, where they tend to disrupt the ecological balance in short period of times. The surveillance of such ecosystems by different technical solutions is complex and dynamic where designing an “optimal” surveillance network, i.e., a network that would reflect an almost realtime situation of an ecosystem. Often traditional optimization techniques fail to reflect the evolutions of the reality associated with these ecosystems.An example of such a situation, is the Mekong Delta region of Vietnam, where the provincial agricultural managers are concerned with the regular invasions of Brown Plant Hoppers (BPH), a particularly active rice pest, because of the diseases they carry and transmit to the rice yields. Their biggest concern is having a constantly accurate account of the current distribution of BPH waves, since it is the basis of establishing different prevention strategies. The time frame is short for applying these strategies: at least one week is needed between the moment where a prediction of the density of BPH can be estimated by the experts and warnings are sent to farmers and other end users and the moment where a strategy can be efficiently applied. To improve the efficiency of the system, the Vietnamese government has established a light-trap network [1] [2] that can capture multiple kinds of insects, especially BPH, and which data (the density of insects per trap) is collected and analyzed daily. Maintaining this network in a good state of operation has become an important national program of the Ministry of Agriculture and Rural Development of Vietnam since 2006. Although the current light-trap network is considered as a necessity for supporting the fight against various plant pests, it has three restrictions: (1) it misses detailed accounts on the life cycle of the BPH, (2) the network has remained stable since its initial design and has not, therefore, completely adapted to the huge changes that the ecosystem of the Mekong Delta has undergone in the recent years especially due to limitations in management, and (3) the network itself is very sparsely distributed
9
Miller, Rachel Weslie Biological Earth & Environmental Sciences Faculty of Science UNSW. "Rattus tanezumi in the upland rice terraces of Banaue, Philippines: demography, habitat use, crop damage and yield assessment." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/38038.
Full textAbstract:
Rodents cause significant damage to agricultural crops throughout the world, including rice, the staple food for the increasing population of Southeast Asia. Little is known about the ecology of pest rodent species, resulting in much effort being concentrated on ineffective, time consuming control practices. This research was designed to understand the demography and habitat use of the major pest rodent (Rattus tanezumi) of the Banaue rice terraces in order to identify the most efficient time and location to undertake pest control. Rodent crop damage and associated yield loss was also assessed in order to provide information for a cost : benefit analysis of rodent control practices. And the beliefs, perceptions and practices of Banaue rice farmers were investigated to assist in identifying future compatible rodent control programs. Replicated cage trapping was undertaken for a twelve month period over the entire rice cropping season in two study sites in the Municipality of Banaue Philippines. The breeding season of R. tanezumi corresponded with periods of food availability from the transplanted to ripening stages of the rice crop. A non-breeding season occurred from the fallow to seedling stages. The distinct breeding season occurred within the rice fields and adjacent village and scrub habitats. Radio-tracked and spool-and-line tracked R. tanezumi moved from adjacent habitats into the rice field during the breeding season, and individuals persisted in all habitat types, including the rice field, during the fallow, nonbreeding season. Overall rice yield was significantly greater (43%) in areas where rodents were excluded by fencing compared to areas where rodents were not excluded. More rodent damage to rice tillers occurred at the booting than at the ripening stage of the rice crop. These results suggest that to prevent rodent damage, control should be undertaken at the end of the R. tanezumi non-breeding season (prior to transplanting), before rodent numbers multiply and crop damage occurs. Further, the cost-benefit analysis of non-chemical rodent control programs in Banaue, suggests that benefits accrue once yield loss is likely to exceed 5%.
10
Pereira, Danilo Augusto dos Santos [UNESP]. "Estrutura genética de populações de Rhizoctonia oryzae-sativae do arroz em São Paulo, Brasil, e em meta, Colômbia, e potencial adaptativo do patógeno à Urochloa spp." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126551.
Full textAbstract:
Made available in DSpace on 2015-08-20T17:10:06Z (GMT). No. of bitstreams: 0
Previous issue date: 2015-03-30. Added 1 bitstream(s) on 2015-08-20T17:27:02Z : No. of bitstreams: 1
000843759.pdf: 1198801 bytes, checksum: a7d728ac692d7c1e17e88074d6859d76 (MD5)<br>O complexo de manchas da bainha do arroz engloba três doenças causadas por diferentes espécies de Rhizoctonia: a queima-da-bainha (causada R. solani AG-1 IA), a mancha agregada da bainha (R. oryzae-sativae) e a mancha da bainha (R. oryzae). Distinguir os agentes causais é um passo crítico para manejá-los eficazmente. Em levantamento recente efetuado em cinco áreas de cultivo de arroz no Vale do Paraíba, Brasil, e nos Llanos na Colômbia, R. oryzae-sativae, o patógeno da mancha agregada da bainha, foi a espécie predominante em ambos os países. Neste estudo, nosso principal objetivo foi determinar a estrutura genética das populações de R. oryzae- sativae do arroz no agroecossistema da região do Vale do Paraíba e nos Llanos Colombianos. Inferiu-se sobre o fluxo gênico entre populações do patógeno, dentro e entre os países, e sobre o modo reprodutivo predominante. Nosso segundo objetivo foi determinar o potencial de duas populações brasileiras de R. oryzae-sativae em adaptar-se a espécies forrageiras do gênero Urochloa. Uma vez que essas espécies de forrageiras são cultivadas em áreas adjacentes ou em rotação com arroz, podem estar exercendo elevada pressão de seleção sobre as populações de R. oryzae- sativae. Análises da estrutura genética de populações foram baseadas na genotipagem de isolados de quatro populações do patógeno usando cinco marcadores microssatélites. Populações próximas e distantes apresentaram indícios de fluxo gênico. Evidências de reprodução sexuada nas populações do patógeno e a baixa fração clonal, indicaram a predominância de um sistema reprodutivo recombinante. É provável que basidiósporos desempenhem papel mais importante no ciclo da doença do que se supunha anteriormente. Isolados das duas populações brasileiras de R. oryzae-sativae foram patogênicos e apresentaram variação na agressividade à Urochloa spp., porém com baixos índices de herdabilidade,...<br>The rice sheath-blight complex comprises three diseases caused by different Rhizoctonia species: sheath blight (caused by R. solani AG-1 IA), aggregated sheath spot (R. oryzae-sativae), and sheath spots (R. oryzae). To be able to distinguish among the causal agents is a critical step in order to manage them effectively. In a recent survey in five rice cropping areas from the Paraíba Valley region, Brazil, and from the Llanos in Colombia, R. oryzae-sativae (the aggregated sheath spot pathogen) was the predominant species on both countries. In this study, our primary objective was to determine the genetic structure of populations of R. oryzae-sativae from rice paddy fields sampled from the Paraiba Valley and the Colombian Llanos. We inferred about gene flow among populations within and between countries and the pathogen's main reproductive mode. The second objective was to infer the potential of the two brazilian populations of R. oryzae-sativae to adapt and become pathogen of forage pastures of the genus Urochloa. Once these forage species are intensively cropped in adjacent areas or under rotation with rice, they might be exerting strong selection pressure on R. oryzae-sativae populations. Population structure analyses were based on genotyping fungal isolates from four populations of the pathogen using five microsatellites markers. Gene flow was detected among geographically close and distant populations. Evidences of sexual reproduction and low clonal fraction found in the populations, indicated the predominance of a mixed reproductive system. It is plausible that basidiospores play a more important role on the disease cycle than previously thought. Isolates from the two brazilian populations of R. oryzae-sativae were pathogenic and varied on aggressiveness to Urochloa spp. However, low levels of heritability for aggressiveness were detected, indicating a yet limited adaptation to Urochloa spp
11
Pereira, Danilo Augusto dos Santos. "Estrutura genética de populações de Rhizoctonia oryzae-sativae do arroz em São Paulo, Brasil, e em meta, Colômbia, e potencial adaptativo do patógeno à Urochloa spp /." Ilha Solteira, 2015. http://hdl.handle.net/11449/126551.
Full textAbstract:
Orientador: Paulo Cezar Ceresini<br>Banca: Antonio de Goes<br>Banca: Daniel Augusto Schurt<br>Resumo: O complexo de manchas da bainha do arroz engloba três doenças causadas por diferentes espécies de Rhizoctonia: a queima-da-bainha (causada R. solani AG-1 IA), a mancha agregada da bainha (R. oryzae-sativae) e a mancha da bainha (R. oryzae). Distinguir os agentes causais é um passo crítico para manejá-los eficazmente. Em levantamento recente efetuado em cinco áreas de cultivo de arroz no Vale do Paraíba, Brasil, e nos Llanos na Colômbia, R. oryzae-sativae, o patógeno da mancha agregada da bainha, foi a espécie predominante em ambos os países. Neste estudo, nosso principal objetivo foi determinar a estrutura genética das populações de R. oryzae- sativae do arroz no agroecossistema da região do Vale do Paraíba e nos Llanos Colombianos. Inferiu-se sobre o fluxo gênico entre populações do patógeno, dentro e entre os países, e sobre o modo reprodutivo predominante. Nosso segundo objetivo foi determinar o potencial de duas populações brasileiras de R. oryzae-sativae em adaptar-se a espécies forrageiras do gênero Urochloa. Uma vez que essas espécies de forrageiras são cultivadas em áreas adjacentes ou em rotação com arroz, podem estar exercendo elevada pressão de seleção sobre as populações de R. oryzae- sativae. Análises da estrutura genética de populações foram baseadas na genotipagem de isolados de quatro populações do patógeno usando cinco marcadores microssatélites. Populações próximas e distantes apresentaram indícios de fluxo gênico. Evidências de reprodução sexuada nas populações do patógeno e a baixa fração clonal, indicaram a predominância de um sistema reprodutivo recombinante. É provável que basidiósporos desempenhem papel mais importante no ciclo da doença do que se supunha anteriormente. Isolados das duas populações brasileiras de R. oryzae-sativae foram patogênicos e apresentaram variação na agressividade à Urochloa spp., porém com baixos índices de herdabilidade,...<br>Abstract: The rice sheath-blight complex comprises three diseases caused by different Rhizoctonia species: sheath blight (caused by R. solani AG-1 IA), aggregated sheath spot (R. oryzae-sativae), and sheath spots (R. oryzae). To be able to distinguish among the causal agents is a critical step in order to manage them effectively. In a recent survey in five rice cropping areas from the Paraíba Valley region, Brazil, and from the Llanos in Colombia, R. oryzae-sativae (the aggregated sheath spot pathogen) was the predominant species on both countries. In this study, our primary objective was to determine the genetic structure of populations of R. oryzae-sativae from rice paddy fields sampled from the Paraiba Valley and the Colombian Llanos. We inferred about gene flow among populations within and between countries and the pathogen's main reproductive mode. The second objective was to infer the potential of the two brazilian populations of R. oryzae-sativae to adapt and become pathogen of forage pastures of the genus Urochloa. Once these forage species are intensively cropped in adjacent areas or under rotation with rice, they might be exerting strong selection pressure on R. oryzae-sativae populations. Population structure analyses were based on genotyping fungal isolates from four populations of the pathogen using five microsatellites markers. Gene flow was detected among geographically close and distant populations. Evidences of sexual reproduction and low clonal fraction found in the populations, indicated the predominance of a mixed reproductive system. It is plausible that basidiospores play a more important role on the disease cycle than previously thought. Isolates from the two brazilian populations of R. oryzae-sativae were pathogenic and varied on aggressiveness to Urochloa spp. However, low levels of heritability for aggressiveness were detected, indicating a yet limited adaptation to Urochloa spp<br>Mestre
12
Roma, Rafaela Carolina Constantino. "Diversidade de fungos associados a manchas em sementes de arroz irrigado com aplicação de silicato de cálcio e cinza de casca de arroz." Universidade Federal de Viçosa, 2010. http://locus.ufv.br/handle/123456789/4374.
Full textAbstract:
Made available in DSpace on 2015-03-26T13:37:41Z (GMT). No. of bitstreams: 1
texto completo.pdf: 321107 bytes, checksum: 908241592d4e38b9e9d64df652b74e85 (MD5)
Previous issue date: 2010-02-10<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The rice crop is of great importance on the world stage because it serves as the main food for millions of people around the world. However, several factors affect its
production, mainly the diseases. The seed spot is caused by various fungi such as Bipolaris oryzae, Pyricularia grisea, Microdochium oryzae, Phoma sorghina, Cladosporium sp. and others. In seeds, this disease can cause reduction on germination and decrease on production due to the sterility of panicles. The application of silicon (Si) has been studied as an alternative in the control of plant diseases. Thus, the aim of this work was to evaluate the effect of calcium silicate and rice husk hulls in the incidence of fungi associated with flooded rice seed. Rice plants were submitted with rice husk hulls and calcium silicate in the doses 0, 153 and 357 kg/ha of Si. Two experiments were performed, one in the 2007/2008 harvest season and another in 2008/2009 and later seed samples were analyzed in the laboratory. Evaluations of Browning Index Seeds (BIS), the Si concentration in the pericarp of the seeds and determination of seedborne fungi were executed. There was no significant difference from the F test for IES and Si concentration for the two sources of Si in the doses used
in both experiments. The efficiency of the products used and the concentration of Si in the pericarp of the seeds were similar, independently of the applied dose. In general, the fungi found in both experiments were Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, F. solani, Microdochium oryzae, Nigrospora oryzae, Pyricularia grisea,
Trichoconiella padwickiii and Cladosporium cladosporioides. The incidence of these fungi was not affected by the application of rice husk hulls or calcium silicate in the
doses used.<br>A cultura do arroz tem grande importância no cenário mundial, pois se faz base da alimentação de milhões de pessoas ao redor do mundo. Porém, vários fatores afetam sua produção, dentre eles, as doenças. As manchas em sementes é causada por diversos fungos como Bipolaris oryzae, Pyricularia grisea, Microdochium oryzae, Phoma sorghina, Cladosporium sp., dentre outros. Em sementes, esta doença pode levar a
redução da germinação e queda na produção devido à esterilidade de panículas. A aplicação de silício (Si) tem sido estudada como alternativa para o auxílio no controle de doenças de plantas. Desta forma, objetivou-se com este trabalho avaliar o efeito da aplicação de silicato de cálcio e de casca de arroz carbonizada na incidência de fungos
associados a manchas em sementes de arroz. Plantas de arroz foram submetidas à aplicação de cinza de casca de arroz e silicato de cálcio nas doses utilizadas foram de 0; 153 e 357 kg/ha de Si. Dois experimentos foram conduzidos, sendo um na safra 2007/2008 e outro na safra 2008/2009 e, posteriormente, amostras de sementes foram
analisadas em laboratório. Foram realizadas avaliações do Índice de Escurecimento de Sementes (IES), da Concentração de Si no pericarpo das sementes e a determinaçãp dos fungos presentes nas sementes. Não foi encontrada diferença significativa a partir do teste F para IES e concentração de Si para as duas fontes de Si empregadas, nas doses
utilizadas nos dois experimentos, ou seja, a eficiência dos produtos utilizados e a concentração de Si no pericarpo das sementes foi semelhante, independente da dose aplicada. Em geral, os fungos encontrados em ambos experimentos foram Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, F. solani, Microdochium oryzae, Nigrospora oryzae, Pyricularia grisea, Trichoconiella padwickiii e Cladosporium
cladosporioides. A incidência destes fungos não foi afetada pela aplicação de casca de arroz carbonizada ou silicato de cálcio nas doses utilizadas.
13
Permual, Dindyal. "Investigations of stored rice pest problems in Guyana." Thesis, Imperial College London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308943.
Full text
14
Mehlo, Luke. "Genetic engineering of rice and maize for insect pest resistance." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301942.
Full text
15
Dunn, Lucinda. "Social and ecological constraints affecting insect pest management in Cambodian rice farming systems." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28103.
Full textAbstract:
Rice (Oryza sativa L.) is the most economically important crop in Cambodia providing smallholder farmers with food and income. Despite rice cultivation being widespread, rice yields in Cambodia are among the lowest in Southeast Asia. Cambodian farmers reported insect pests to be the leading cause of yield loss. To control pests, farmers are dependent on pesticides without any integrated pest management (IPM) options employed. My research aimed to establish ecological and social entry points for successful IPM adoption using a farmer-focused approach. The overarching research question was what are the main social and ecological constraints of rice pest management in NW Cambodia, and how are these constraints hindering IPM adoption. To do this, I undertook an interdisciplinary mixed method approach. Firstly, I examined how spatial position within a rice field and field characteristics (vegetation cover and presence of water) affected pest and natural enemy abundance, richness, and diversity. I then undertook a survey with smallholder rice farmers on their knowledge, attitudes, and practices (KAPs) regarding insect pests, insecticide use, and farm management information. In addition, I explored the different kinds of information sources farmers use and trust the most for reliable pest management advice. By taking a holistic approach to understanding the rice agroecosystem, my thesis identified several points of intervention to improve ecologically and sociologically sustainable pest management for smallholder rice farmers in Northwest Cambodia.
16
Jackson, Sydni Blaine. "Adoption and Impacts of IPM for Cambodian Rice Farmers." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/80412.
Full textAbstract:
This study evaluates the adoption and impacts of Integrated Pest Management (IPM) adoption for rice in Cambodia. Extent of adoption and characteristics of adopters are discovered. Farmers are considered high adopters of IPM if they used two non-pesticide or minimal-pesticide practices to control rice insect, disease, weed, or rodent pests in the last twelve months; farmers are considered low adopters if they used one practice; farmers are considered non-adopters if they used zero practices. IPM practices include pest-resistant variety; stale seedbed (sequential harrowing or harrowing followed by a non-selective herbicide); apply Trichoderma on seeds or seedlings, no insecticide spray for the first 40 days; apply bio-pesticides such as neem, Bt, and metarhizium, and Beauvaria; Sarcocystis bait for rodents; hand weeding at recommended growth stage; and/or another practice specified by the farmer.
Out of 394 farmers surveyed, 40 (10.15%) were found to be high adopters, 228 (57.86%) were found to be low adopters, and 126 (31.97%) were found to be non-adopters of IPM. IPM practices currently include mostly hand-weeding and no spray for 40 days; few other practices were adopted. Our study reveals a need for broader education on rice IPM throughout Cambodia. The high frequency of pesticide applications among rice farmers, the finding that adoption of IPM was not found to have a meaningful influence on the number of pesticide applications, and the finding that less than one-quarter of farmers in our study have received training on IPM reveal the need for increased knowledge of IPM in Cambodia, and the need for future education on IPM to focus on reducing pesticide use.<br>Master of Science
17
Mamaril, Cezar Brian Castillo. "Transgenic Pest Resistant Indica Rice: An Ex-ante Economic Evaluation of an Adoption Impact Pathway in the Philippines and Vietnam for Bt Rice." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/30896.
Full textAbstract:
Research and development of Bt rice in Southeast Asia has been overshadowed by the contentious debate over the potential release of transgenic food crops into the region. The study provides empirical evidence on the potential size and distribution of economic benefits of adopting Bt Indica rice in the Philippines and Vietnam through the years 2000 to 2020. Total welfare gains from Bt rice are projected at 618.8 million USD (discounted at 5 percent) and aggregate benefits by region are projected at 269.6 million USD for the Philippines, 329.1 million USD for Vietnam, and 20.1 million USD for the rest of the world. Simulation results indicate that producers in both countries will capture 66.5 percent of the total welfare effect from Bt rice adoption, 25.9 percent will accrue to consumers, 3 percent to the rest of the world, and the loss in Philippine government revenue accounts for 4.6 percent of the total welfare effect. The study also reports how other factors will determine the size and distribution of economic benefits of Bt rice.
<p><i>Vita removed, Sept. 13, 2012, GMc</i></p><br>Master of Science
18
Collins, Nicholas C. "The genetics of barley yellow dwarf virus resistance in barley and rice." Title page, table of contents and summary only, 1996. http://hdl.handle.net/2440/46063.
Full textAbstract:
Barley yellow dwarf virus (BYDV), an aphid transmitted luteovirus, is the most widespread and economically damaging virus of cereal crops. The work in this thesis aims to characterise the basis of the naturally occurring resistance to BYDV in cereals in three ways: Firstly, by facilitating the isolation of the Yd2 gene for BYDV resistance from barley by a map-based approach. Secondly, by determining if a BYDV resistance gene in rice is orthologous to Yd2. Thirdly, by establishing if other BYDV resistance genes in non- Ethiopian barleys are allelic to Yd2. It is hoped that the information generated in this study will ultimately assist in the production of BYDV resistant cereal cultivars. A detailed genetic map of the Yd2 region of barley chromosome 3 was constructed, containing 19 RFLP loci, the centromere and the Yd2 gene. Yd2 mapped on the long arm, 0.5 cM from the centromere, and in the mapping population of 106 F2 individuals, perfectly cosegregated with the RFLP loci XYlp, and Xwg889. This map represents the first stage in a project to isolate the Yd2 gene by a map-based approach. The isolation of Yd2 could help to elucidate the molecular mechanism of the Yd2-mediated BYDV resistance, and may allow the production of BYDV resistant cereals by genetic transformation. The RFLP markers mapped closest to Yd2 could also be useful in barley breeding, by enabling selection for both the presence of Yd2 and the absence of agronomically undesirable traits known to be closely linked to Yd2. Genetically Directed Representational Difference Analysis (GDRDA) is a technique based on subtractive hybridisation, which can be used to identify RFLP markers closely linked to a gene of interest. Two GDRDA experiments were performed with the intention of generating additional RFLP markers close to Yd2. However, the first experiment yielded RFLP probes that were not derived from the barley genome, while the second experiment yielded probes that detected repetitive sequences. It was concluded that GDRDA is of limited use in generating further markers close to Yd2. To isolate the Yd2 gene by a map-based approach, a much larger mapping population will need to be analysed to genetically resolve markers tightly linked to Yd2. If the two morphological markers uzu dwarf and white stripe,,j flank Yd2, then they could assist in this task by enabling the visual identification of F2 seedlings resulting from recombination close to Yd2. However, in this study, both morphological markers were found to be located distal to Yd2. Therefore, these two morphological markers can not be used together to facilitate high resolution genetic mapping of the Yd2 locus. It may be possible to use large-insert genomic DNA clones from the relatively small genome of rice to generate further RFLP markers close to the Yd2 gene in barley, provided that the order of orthologous sequences in barley and rice is conserved close to the Yd2 locus. To assess the feasibility of this approach, RFLP probes used to identify loci close to Yd2 were mapped in rice using a segregating rice F2 population. Five of the RFLP loci mapped together and in the same order as RFLP loci mapped close to Yd2 in barley using the same probes. By comparing the location of RFLPs mapped by other researchers in rice using probes mapped close to Yd2, the region of conserved linkage between rice and the Yd2 region was tentatively identified as the central portion of rice chromosome 1. The collinearity shown by orthologous sequences in barley and rice indicated that it may indeed be possible to use rice to assist in generating RFLP markers close to Yd2. Of all the cereals, rice is the most amenable to map-based gene isolation, due to its small genome, well developed physical and genetic maps, and its ability to be genetically transformed with high efficiency. If a BYDV resistance gene that is orthologous to Yd2 could be identified in rice, this gene could be isolated with relative ease, and then used to identify barley cDNA clones corresponding to Yd2 gene by virtue of the sequence homology expected between these genes. To test if a BYDV resistance gene from an Italian rice line is orthologous to Yd2, recombinant-inbred rice lines previously characterised for this gene were analysed using probes mapped close to Yd2 in barley. No genetic linkage was detected between the RFLP loci and the BYDV resistance gene, indicating that the gene is unlikely to be orthologous to Yd2. BYDV resistance alleles at the Yd2 locus which are of a non-Ethiopian origin may show interesting differences to Ethiopian Yd2 resistance alleles. To identify barleys which may contain resistance alleles of Yd2, ten BYDV resistant barleys not known to contain Yd2 were assessed for their resistance to the PAVadel isolate of BYDV in the glasshouse. CI 1179, Rojo, Perry, Hannchen, Post and CI 4228 were found to be the most resistant under these conditions, and were analysed further. If the resistance from these barleys is controlled by alleles of Yd2, RFLP markers close to Yd2 will be expected to cosegregate with the resistance in F2 families derived from crosses between these resistant barleys and the BYDV susceptible barleys Atlas and Proctor. RFLPs suitable for use in these allelism tests were identified using probes mapped close to Yd2. However, time did not permit the analysis of these F2 populations.<br>Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Science, 1996
19
Baptista, Jean Tiago. "Fomes, pestes e guerras : din?micas dos povoados missionais em tempos de crise (1610-1750)." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2007. http://tede2.pucrs.br/tede2/handle/tede/2545.
Full textAbstract:
Made available in DSpace on 2015-04-14T13:48:30Z (GMT). No. of bitstreams: 1
397384.pdf: 192236 bytes, checksum: 8c9dce6673543470935b9e4bff3e895b (MD5)
Previous issue date: 2007-11-06<br>Este estudo se dedica ? din?mica das popula??es missionais do Paraguai Eclesi?stico em per?odos de crises, particularmente durante epis?dios relacionados ?s fomes, epidemias e guerras. As diversas articula??es identit?rias e os m?ltiplos caminhos escolhidos pelos ind?genas dos povoados demonstram o quanto as crises puderam servir de est?mulo ? gera??o de debates com os jesu?tas sobre importantes pr?ticas e cren?as. Com isso, aquelas popula??es participavam de forma ativa na elabora??o de uma pastoral, ou seja, um conjunto de vers?es e propostas eficientes ou criativas, com freq??ncia amb?guas ou tensas, voltadas ? constru??o de um modo de vida conectado ou vi?vel ao mundo colonial em que se envolviam
20
Brown, Preston Hunter. "Spatiotemporal Composition of Pest Ant Species in the Residential Environments of Santa Isabel, Puerto Rico." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/33122.
Full textAbstract:
Few studies have evaluated the community dynamics of pest ant species in tropical urban environments. Pest ant community dynamics were examined within three Puerto Rican housing developments. Housing developments (one, four, and eight years old), representing different stages of urban succession were sampled to determine which species were present and the relative species abundance. Eight trips were made to Puerto Rico over a one-year period, and more than 1,000 samples were collected during each trip. The ants collected in each sample were counted and identified. A total of 25 different species were identified from the developments, with the major pest species being big-headed, rover, and red imported fire ants (RIFA). Fourteen different species were identified from the one-year-old site. However, RIFA and rover ants were the most abundant, accounting for >75% of ants collected. In the four-year-old site, 20 species were identified. However, three species (RIFA, big-headed, and destructive trailing ants) were dominant, accounting for >75% of ants collected. Sampling data from the eight-year-old site indicated that out of 21 species identified, four species were dominant (RIFA, crazy, and two species of big-headed ants) and accounted for >75% of the ants collected. The dominant species within each site were different, indicating that the pest ant community changed during the stages of succession. However, these dominant species did not specifically impact the distribution of other species within the same site. Spatial analysis indicated that the number of species coexisting within a site increased as the age of the development increased.<br>Master of Science in Life Sciences
21
Garcia, Dario Cardenas. "The nutritional evaluation of Colombian rice polishings as a feed supplement for ruminants." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU601996.
Full textAbstract:
The aims of the present study were to evaluate the suitability of Colombian rice polishings (RP) as a feed supplement for ruminants and to study its effect on rumen fermentation. The quality of RP appeared to be uniform and independent of the period of the year when the RP were collected. The low content of particles greater than 2 mm2 separated on sieving, combined with the low ash content suggested that the RP used in the current studies contained little broken rice or rice hulls. The proximate analysis of RP suggested a by-product which represented a good source of carbohydrates (starch), protein and phosphorus, but contained a high fat concentration (254, 143, 12.7 and 180 g/kg DM respectively). Of the total fatty acids in the oil 0.77 were unsaturated. Full-fat RP were fermented in the in vitro Menke system less efficiently than other substrates containing medium quality hay, starch or cellulose, but were apparently more degradable when measured in sacco. However, for each diet at 4, 8, 24, and 48h incubation there was a significant correlation (r2=0.97) between the amount of DM degraded in sacco and the gas production measured in vitro (P<0.01)'. The evaluation of RP in the in vitro Rusitec system indicated that any adverse effects of high lipid concentration of RP, such as the potential for an inhibition in bacterial growth, appeared to be outweighed by a nonsignificant stimulation in microbial activity resulting from the inclusion of this rapidly degradable substrate in the diet. An in vivo study with adult sheep suggested that at the level tested RP, as an alternative to urea molasses did not increase the efficiency of rumen fermentation and were not as effective a supplement with urea as molasses for a low quality forage diet. Measurements of in vitro fermentation of sieved fractions suggested that the rate of degradation in the rumen fluid decreased as particle size increased in excess of 2 mm2, in vitro batch culture results suggested that RP crude protein is highly and rapidly degraded in the rumen. In the current study RP were a rapidly degradable substrate in the rumen, represented a source of RDP and the high ammonia concentration recorded may indicate an intraruminal n recycling possibly due to an enhanced Protozoal population.
22
Cerda, Rolando. "Assessment of yield and economic losses caused by pests and diseases in a range of management strategies and production situations in coffee agroecosystems." Thesis, Montpellier, SupAgro, 2017. http://www.theses.fr/2017NSAM0004/document.
Full textAbstract:
Les pertes de récolte dues aux ravageurs et aux maladies constituent une menace sérieuse pour les revenus et la sécurité alimentaire de milliers de familles rurales dans le monde entier. L'évaluation de ces pertes de récolte (baisse de rendement et préjudice économique) et de leurs causes est nécessaire pour améliorer la mise au point d'agroécosystèmes capables d'offrir de bons rendements de culture, une régulation des ravageurs et des maladies et d'autres services écosystémiques. Ce mémoire de doctorat vise à contribuer à la recherche dans le domaine des pertes de récolte en proposant des approches expérimentales et de modélisation susceptibles d'être utilisées pour estimer les pertes primaires et secondaires subies dans les cultures pérennes, et analyser leurs causes. La culture pérenne étudiée est celle du caféier à Turrialba au Costa Rica, où la culture du café se pratique dans des plantations qui vont de la monoculture à pleine exposition solaire à des systèmes agroforestiers hautement diversifiés, et qui sont soumises à une gamme de situations de production (topolimat, fertilité du sol, types d'ombrage) et de stratégies de gestion (pratiques culturales et intrants). Les trois questions de recherche principales ont été les suivantes : Quel est l'impact des stratégies de gestion et des situations de production sur les ravageurs et les maladies et les rendements en café ? Comment les pertes de rendement en café associées à des profils de dégâts donnés varient-elles en fonction des stratégies de gestion et des situations de production ? Quels types d'agro-écosystèmes à base de caféiers permettent de minimiser les pertes en café (baisse de rendement et préjudice économique) et de maximiser les avantages globaux retirés (services écosystémiques) ?<br>Crop losses due to pests and diseases are a major threat to incomes and food security of thousands of rural families worldwide. The assessment of crop losses (yield and economic losses) and their causes is needed to improve the development of agroecosystems capable to offer good crop yields, regulation of pests and diseases, and other ecosystem services. This doctoral research aimed to contribute to the research field of crop losses, by providing experimental and modeling approaches that could be used in perennial crops to estimate primary and secondary losses and analyze their causes. We worked in a perennial crop such as coffee, in Turrialba, Costa Rica, where coffee is grown in plantations from monocultures at full sun exposure to highly diversified agroforestry systems, and under a range of production situations (topoclimate, soil fertility, types of shade) and management strategies (agricultural practices and inputs). The three main research questions were: What is the impact of management strategies and production situations on pests and diseases and coffee yields? How do coffee yield losses caused by injury profiles vary in function of management strategies and production situations? Which types of coffee agroecosystems are capable to obtain the lowest coffee losses (yield and economic) and highest overall benefits (ecosystem services)? This research was developed through two experimental designs. The first was an experimental coffee parcel under controlled conditions (three-year experiment) to quantify primary and secondary yield losses by comparison of treatments, and to identify the main predictors of yield losses by structural equation modeling. The second experimental design was based on surveys in a coffee research plot network (coffee plots of smallholder farmers), where, during two years, we measured indicators of yields and indicators of four ecosystem services: regulation of pests and diseases, provisioning of agroforestry products, maintenance of soil fertility, and carbon sequestration. Yield losses in this network were estimated through modeling using the predictors identified in the experimental coffee parcel. Analyses of data included several statistical techniques, from analysis of variances, linear regressions to multivariate techniques. The results were organized in four manuscripts, and then discussed integrally. The main findings were: i) Both production situations and management strategies determine coffee yield and pest and disease injuries, effects of interactions altitude x management x types of shade must be considered; ii) Injury profiles depend on particular combinations of production situations and management strategies, with impacts on yield losses especially in a year of high coffee production (primary yield losses), but compromising also the yields of the next year (secondary yield losses); iii) Diversified agroforestry systems have better chances to regulate pests and diseases (reduce yield and economic losses), and simultaneously provide goods for family benefits, maintain soil fertility, and increase carbon sequestration, without implying trade-offs among these ecosystem services. The main prospects of this research are related to perform similar studies in coffee and other perennials at regional levels, develop an injury profile simulator for coffee, and prototyping of coffee agroforestry systems to optimize the provision of multiple ecosystem services
23
Laura, Liliana Abril Garcia. "Population Dynamics of the Brown Planthopper Nilaparvata lugens (Stål) in Rice Fields in Thailand and Its Potential Applications to Pest Management." Kyoto University, 2018. http://hdl.handle.net/2433/232366.
Full textAbstract:
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第21165号<br>農博第2291号<br>新制||農||1060(附属図書館)<br>学位論文||H30||N5139(農学部図書室)<br>京都大学大学院農学研究科地域環境科学専攻<br>(主査)教授 縄田 栄治, 教授 舟川 晋也, 教授 松浦 健二<br>学位規則第4条第1項該当
24
FRANCO, JOSE G. "Efeitos da radiacao microondas nas diferentes fases do ciclo evolutivo de Sitophilus oryzae (Linne, 1763) (Coleoptera, Curculionidae) em arroz, visando o seu controle." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10968.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:46:15Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:01:47Z (GMT). No. of bitstreams: 1
07918.pdf: 1990212 bytes, checksum: d5a68c2dcab7abe1c8ff25f5d20b0a7d (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
25
Harris, Leah M. "Modeling a Cost-Effective IPM Dissemination Strategy for Vegetables and Rice: An Example in South Asia." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/33404.
Full textAbstract:
Integrated Pest Management (IPM) technologies have proven to be effective at increasing agricultural productivity and have been credited for providing economic, health, and environmental benefits in many developing countries. In South Asia, population growth and the increasing demand for nutritious foods have put pressure on farmers to produce more food with a relatively inelastic supply of land. Productivity enhancing practices, like IPM, have helped some farmers to meet this demand; however, with over 50 million farmers in Bangladesh and Nepal it is difficult to reach them with information about new agricultural technologies. This study evaluates the current IPM dissemination strategy being implemented by the Bangladesh Department of Agricultural Extension (DAE) and uses a linear programming (LP) model to propose alternative strategies that may extend the total benefits from IPM technologies. Additionally, using data from a household survey, a bivariate probit model and a two-step endogenous participation model are used to identify factors that may influence both knowledge and adoption of IPM practices in three regions of Nepal. The results from the LP model suggest that more farmers could be effectively reached by reallocating funding that is currently used for interpersonal communications (i.e. extension agent visits and farmer field schools) to more widespread methods such as mass media and field days. The model also suggests that a dynamic dissemination strategy is necessary to encourage adoption of IPM technologies with differing characteristics and levels of complexity. The econometric analysis suggests that farmers with â network linkagesâ to agricultural information and inputs, such as membership in a farmer organization, are more likely to be aware of IPM and to adopt IPM practices. The survey data also suggest that farmers who are members of Marketing Planning Committees (MPC) may be more likely to adopt more IPM practices when compared to non-members. Overall, the study suggests that strategically disseminating IPM information is vital to promote the adoption of these technologies in South Asia.<br>Master of Science
26
Atabila, Albert. "Human Health Risk Assessment and Management of Chlorpyrifos Exposure among Rice Farmers in Ghana." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/378754.
Full textAbstract:
Pesticides are commonly applied in the agricultural sector of Ghana by farmers. Owing to weaknesses in regulations and unsafe practices, applicators of pesticides in the country are vulnerable to excessive exposure and consequent health risks. However, there is no information on the levels of pesticide exposure and associated health risks among applicators in Ghana. In addition, the rice sector of Ghanaian agriculture has been growing in recent years, with significant use of pesticides among commercial growers. Therefore, the objectives of this study were to evaluate the patterns, determinants, magnitude and health risks of pesticide exposure among rice farmers in Ghana. In order to achieve the objectives, a representative cross-section of small-scale farmers who grow rice with irrigation in the catchment area of Kpone Irrigation Scheme (KIS) were recruited for the study. The research was based on the four-step health risk assessment framework of the United States’ National Research Council, which is generally accepted by regulatory agencies and researchers. Thus, the research involved hazard identification, exposure assessment, dose-response assessment and risk characterization. The hazard identification study with the farmers (n = 214), which was carried out by questionnaire survey, showed that chlorpyrifos was the most widely used pesticide with usage prevalence of 83%. The study also showed that pesticides were applied under unsafe conditions and all applicators had experienced symptoms compatible with pesticide poisoning, as described by the WHO. Evaluation of exposure to chlorpyrifos among the applicators during a typical spray event was carried out, based on two approaches. These were (1) whole-body dosimetry assessment of dermal exposure, using Tyvek coverall, hand gloves and socks to sample chlorpyrifos residues of applicators (n = 24); and (2) urinary trichloro-2-pyridinol (TCP) assessment of overall exposure from six urine samples (one sample collected prior to application and five samples collected over five days after application) from each applicator (n = 21). The dermal exposure study showed that the percentage Unit Exposure (UE) value calculated from Total Dermal Exposure (TDE) was 0.03% and 0.06% among the median-exposed and the 5% highly-exposed groups, respectively. The study also indicated that the hands (39% of TDE) and the lower anatomical (82% of TDE) regions of the applicators were the most contaminated and potential sources of dermal exposure. The urinary TCP assessment indicated that the mean elimination half-life (t1/2) of chlorpyrifos in the body of the applicators was 50 hours, which is higher than those (27 to 43 hours) previously reported. The median absorbed dose of chlorpyrifos estimated from urinary TCP due to chronic background exposure (LADDB), chronic application exposure (LADDA) and acute application exposure (ADDA) were 0.2 μg/kg/day (mean ± S.D of 0.3 ± 0.4 μg/kg/day), 0.1 μg/kg/day (mean ± S.D of 0.3± 0.3 μg/kg/day) and 6 μg/kg/day (mean ± S.D of 19 ± 24 μg/kg/day). The absorbed daily dose of chlorpyrifos estimated from urinary TCP and whole-body dermal dosimetry methods produced similar exposure estimates, based on the means ± S.D (15±22 and 16±7 μg/kg/day, respectively), with applicators who participated in both evaluations. The levels of chlorpyrifos exposure from occupational application were positively influenced by the quantity of chlorpyrifos formulation applied, spraying duration, the number of spray tanks applied and the height of the crops sprayed (p < 0.05). To evaluate the dose-response of chlorpyrifos, exposure data from human epidemiological studies from the scientific literature were collated. The exposure data associated with adverse effects were expressed as Cumulative Probability Distributions (CPDs) to obtain the Toxicant Sensitivity Distributions (TSDs) of chlorpyrifos for chronic and acute adverse effects. A guideline value determined at the 5th percentile of the TSD for chronic and acute adverse effects was 0.5 and 2 μg/kg/day, respectively. These guideline values derived with the TSD method are directly applicable to humans without the need for safety factors. On the other hand, conventional guideline values established by regulatory institutions require the application of safety factors when the No Observable Adverse Effect Level (NOAEL) or Lowest Observable Adverse Effect Level (LOAEL) methods are used. Except for the guideline values set by the WHO which gave HQ < 1, those of the USEPA, APVMA and the TSD threshold dose at the 5th percentile gave HQ > 1, suggesting adverse health effects would be observed among the applicators. The percentages of the applicators who were likely to suffer adverse effects due to chlorpyrifos exposure were quantified with the Overall Risk Probability (ORP) and the Monte Carlo Simulation (MCS) techniques. The ORP and the MCS techniques showed that between 1 to 3%, 2 to 4% and 5 to 8% of the applicators were likely to suffer chronic adverse effects due to chlorpyrifos exposure from background, occupational application and combined exposure from background and occupational application, respectively. Such chronic health effects may include altered thyroid functions and reductions in estradiol levels, based on the TSD. Also, the ORP and MCS techniques showed that between 31 to 33% and 32 to 34% of the applicators were likely to suffer acute health effects due to exposure from occupational application and combined exposure from background as well as occupational application, respectively. Comparison of these values with the TSD suggests that the acute health effects likely to be suffered by the applicators can include depression of cholinesterase activity, sub-clinical neuropathy and memory problems, particularly with occupational exposure. Recommendations proposed for adoption by government institutions to help reduce pesticide exposure and associated health effects among the applicators, include provision of training and technical services to enhance adoption of Integrated Pest Management (IPM), promoting use of less toxic pesticides, regular training of farmers and Agricultural Extension Officers (AEOs) on pesticide safety and regular monitoring of exposure among applicators. It is also recommended that farmers should avoid excessive pesticide use, reduce spray duration, reduce number of spray tanks, practice good hygiene and use adequate PPE, particularly for the hands and the lower anatomical regions of the body.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Environment and Sc<br>Science, Environment, Engineering and Technology<br>Full Text
27
Ortigues, I. "Nutrient supply, growth and calorimetric efficiency in heiffers offered straw rich diets." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376818.
Full text
28
Smith, Caroline Louise. "Biological control of root-knot nematodes (Meloidogyne spp.) with Pasteuria penetrans and Verticillium chlamydosporium in Costa Rica." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297317.
Full text
29
Tinjuangjun, Porntip. "Transfer of pest and disease resistance genes to varieties of Thai rice (Oryza sativa L.) : enhancing transformation efficiency using a novel bombardment and selection system." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323239.
Full text
30
Williams, Donald L. "Preliminary evaluation of the rice blast fungus (Magnaporthe grisea) as a potential bioherbicide control agent for crabgrass (Digitaria sanguinalis) infestations of tall fescue (Festuca arundinacea Schreb. cv. Fawn) turf." Virtual Press, 1998. http://liblink.bsu.edu/uhtbin/catkey/1117114.
Full textAbstract:
This study addressed the possibility of rice blast fungus (Magnaporthe grisea) as a potential bioherbicide for the control of crabgrass (Digitaria sanguinalis), in turf/lawn plantings. Experiments were: (i) evaluation of the effect of bioherbicide inoculum dosage (titer) on disease severity in crabgrass; (ii) competition between crabgrass and tall fescue (Festuca arundinacea Schreb. 'Fawn') and the additive effect of rice blast bioherbicide on the competitiveness of crabgrass; (iii) survival of rice blast spores under non-conducive infection conditions on crabgrass; and (iv) effect of multiple inoculations of rice blast fungus and subsequent disease on crabgrass.Spore concentrations of 5 x 105 to 1 x 106 conidia/mI had no significant difference in effect on mean biomass reduction of treated crabgrass. All produced tissue death and loss of vigor in treated crabgrass, but no plant death. In one trial, a spore concentration of 2 x 106 conidia/ml produced 100% biomass loss in treated crabgrass.Competition studies indicated crabgrass will out-compete fescue 'Fawn' in plots of equal numbers of each plant, i.e., 3 fescue and 3 crabgrass. In 10 x 10 cm mini-lawns of fescue interspersed with 5 crabgrass plants, fescue will out-compete the crabgrass. In mini-lawns of fescue and crabgrass, infection of crabgrass with non-lethal doses of rice blast fungus improved fescue's ability to out-compete crabgrass. Three methods of investigating competition were tested. Mini-lawns sown with 0.5 g fescue seed (approx. 200 seeds) with crabgrass seed sown into centers of the four quadrants and in center of the mini-lawn, worked best.Survival of Magnaporthe grisea conidia under non-conducive conditions was tested by drying inoculated crabgrass seedlings for 0-48 hours prior to dew-deposition. Treatments verified spores remain viable at least 24 hours on crabgrass leaves under greenhouse conditions (25-40° C and 25-75% relative humidity).Two successive inoculations (at 3 days and 7 days after primary inoculation) of crabgrass with M. grisea conidia (5 x 105 conidia/ml) resulted in significant reduction in growth compared to a single spore application.Results suggested Magnaporthe grisea exhibits potential for future development as a commercial bioherbicide to control crabgrass (Digitaria sanquinalis). Current studies investigated integration in lawn grass, but should be applicable to situations anywhere crabgrass is considered a weed e.g., in corn (Zea mans) or soybeans (Glycine max).<br>Department of Biology
31
Bayer, Jessica Christine. "Biotechnologies in the Philippines: The Cost of Regulation." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/33482.
Full textAbstract:
Biotechnologies potentially have significant benefits for developing countries but many countries lack complete regulatory processes to allow their release. In evaluating the potential benefits of genetically modified crops, one must be able to measure the true cost of regulations in addition to the other costs associated with bringing the crop to market. The objectives of this paper are to (1) identify the direct costs of the regulation of Bt eggplant, Bt rice, ringspot virus resistant (PRSV) papaya and virus resistant tomatoes in the Philippines, and (2) estimate the opportunity cost of time lost in the regulatory process. The study compares the cost of regulations as they differ by factors such as the existence of previous studies on the product or the intention for export or domestic use. It is hypothesized that the costs are greater for products that are intended for export or human consumption or are produced by the private sector. It is also hypothesized that these factors increase the time to complete the regulatory process, therefore increasing the opportunity cost of time.
This study evaluates the economic impact of the GMO regulatory process on the change in producer surplus, the net present value and the internal rate return using an economic surplus model. Scientists and other experts in the field of GMOs and regulation were interviewed to obtain the necessary data on the regulatory process. The evaluation was carried out for four different commodities in the Philippines, Bt Rice, Bt Eggplant, PRSV Papaya and MVR Tomato. The results for the open economy model revealed a change in producer surplus, as a result of the GMO research, of $418.3 million for Bt Rice and $353.7 million for PRSV Papaya. The closed economy model of Bt Eggplant has a change in producer surplus of $25.1 million and a change in total surplus of $40.8 million while the result for the change in producer surplus for MVR Tomato is $19.3 million and the change in total surplus is $51.6 million. A sensitivity analysis of the results was then carried out in which the elasticity of supply, the cost of regulation, and the release date were each varied in order to show the welfare impact of such changes. The sensitivity analysis revealed limited changes in surplus when elasticity and regulatory costs were changed. However, changing the date of release or commercialization resulted in monumental changes in surplus.<br>Master of Science
32
Taşcı, Yasemin. "Modeled Affinity Constants for Phosphorus Adsorption and Desorption due to Saltwater Intrusion." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7966.
Full textAbstract:
It is important to understand the processes that regulate phosphorus (P) fluxes to coastal environments, because P is an important nutrient in coastal ecosystems. Phosphorus adsorbs to the surface of minerals in sediment and bedrock, and an influx of seawater can cause some of that P to desorb, raising the P concentration of ambient water. Although seawater-induced P desorption is thought to be an important source of P to coastal environments, the chemical reactions that underlie it have not been established. Previous work provides some relevant surface reactions and associated affinity constants between various aqueous P species and the surface of calcite and in dilute calcium carbonate-P solutions. However, these reactions with their respective affinity constants from the literature fail to predict the behavior of P with calcite in seawater. In this study, we conducted a series of batch experiments involving both adsorption and desorption of P in seawater, freshwater, dilute seawater, and mixtures of seawater and freshwater. We used these results in the geochemical model PHREEQC and the parameter estimation model PEST to optimize the affinity constants for the existing surface reactions. We found that after making minor adjustments to the affinity constants, the existing surface complexation models of calcite surface reactions from the published literature are sufficient to explain seawater-induced P desorption. Specifically, our results suggest that CaPO4- and either CaHPO40 or HPO42- may be important species in the P adsorption/desorption reactions in freshwater-seawater mixing.
33
Gidoin, Cynthia. "Relations entre structures de peuplement végétal et bioagresseurs de la culture principale dans les agroforêts tropicales. Application aux agroforêts à cacaoyers et à 3 bioagresseurs : la moniliose (Moniliophthora roreri) au Costa Rica, la pourriture brune (Phytophthora megakarya) et les mirides (Sahlbergellasingularis) au Cameroun." Thesis, Montpellier, SupAgro, 2013. http://www.theses.fr/2013NSAM0027/document.
Full textAbstract:
La valeur potentielle des agro-forêts tropicales comme modèle d'intensification écologique de l'agriculture est un sujet d'intérêt croissant. Les agro-forêts tropicales sont des agroécosystèmes caractérisés par une forte diversité végétale et une diversité d'organisation spatiale des individus. Les structures complexes de ces agroécosystèmes en font des systèmes « proches » des écosystèmes naturels. Cette complexité améliorerait la fourniture de nombreux services écosystémiques. Dans ce travail, nous nous sommes intéressés au service de régulation naturelle des bio-agresseurs des cultures. Notre hypothèse est que la complexité de structure (composition et structure spatiale) des agro-forêts influence la présence et l'intensité d'attaque des bio-agresseurs de la culture principale. En effet, l'augmentation de la diversité végétale à l'échelle de la parcelle diminuerait l'intensité d'attaque de bio-agresseurs spécialistes via la diminution de l'abondance de la ressource. Inversement, cette diversité amplifierait celle des bio-agresseurs généralistes via l'introduction potentielle d'hôtes alternatifs. Une diversité de structures spatiales d'individus associés est aussi susceptible d'influencer le microclimat et par son biais les bio-agresseurs des cultures. Pourtant, l'importance relative de l'effet de la composition (via la dilution ou l'amplification de la ressource) et de la structure spatiale (via l'altération du microclimat) du peuplement végétal sur l'intensité d'attaque de bio-agresseurs a rarement été étudiée. L'objectif de ce travail est de quantifier les interactions entre les caractéristiques de composition et de structure spatiale du peuplement végétal d'agroécosystèmes complexes et l'intensité d'attaque de bio-agresseurs de la culture principale à l'échelle de la parcelle. Ce travail est appliqué aux agro-forêts à cacaoyers du Costa Rica et du Cameroun. En effet, la culture du cacaoyer est l'une des rares encore réalisée traditionnellement au sein d'agro-forêts dans la majorité des pays producteurs. Nous nous intéresserons à trois bio-agresseurs du cacaoyer choisis pour leurs caractéristiques de dissémination et de développement contrastées : au Costa Rica, la moniliose sur un réseau de parcelles installées dans la région de Talamanca ; au Cameroun la pourriture brune et les mirides sur un réseau de parcelles installées dans la région Centre. Dans un premier temps nous avons construit des typologies descriptives des structures spatiales des agro-forêts à cacaoyers du Costa Rica et du Cameroun afin d'identifier la variabilité des structures spatiale des agro-forêts au sein d'une même région. Ces typologies ont permis d'identifier des structures spatiales horizontales variées allant de la régularité à l'agrégation significatives des arbres d'ombrage selon les pays étudiés. Dans un deuxième temps nous avons identifié et hiérarchisé les caractéristiques de composition et de structure spatiale à l'échelle de la parcelle agroforestière qui influencent l'intensité d'attaque de la moniliose au Costa Rica ; et de la pourriture brune et des mirides au Cameroun. La structure spatiale du peuplement végétal joue un rôle prépondérant dans l'ensemble de nos résultats. L'agrégation des arbres forestiers augmente l'intensité d'attaque de la moniliose au Costa Rica et la densité des mirides au Cameroun. La pourriture brune quant à elle augmente lorsque la densité des individus de la strate basse augmente à l'échelle de la parcelle. Pour finir, nous montrons que la quantité de tissus sensible plutôt que la composition en hôte explique l'intensité de la moniliose et la densité en miride. Ces résultats sont discutés en fonction des nombreux mécanismes qui relient la structure de la végétation aux bio-agresseurs et des caractéristiques de ces bio-agresseurs. Notre travail fournit une description précise de la structure d'agro-écosystèmes tropicaux complexes<br>The potential value of tropical agroforests as a model for ecological intensification of agriculture is a subject of increasing interest. Tropical agroforests are agroecosystems characterized by high plant diversity and a complex spatial structure of individuals. With their forest-like structures, agroforests are close to natural ecosystems. The complex structure of agroforests would seem to improve the provision of numerous ecosystem services.This work concerned natural pest and disease regulation services in complex agroecosystems. Our hypothesis was that complex agroforest structures (composition and spatial structure) influence the pest and disease attack intensity on the main crop. Indeed, an increase in plant diversity in agroecosystems is known to reduce specialized pest and disease attack intensity due to a decrease in resource abundance and density on a plot scale. Conversely, plant diversity could increase the generalist pest and disease attack intensity due to the potential introduction of alternative hosts. Moreover, diversity in plant spatial structure has an impact on microclimatic conditions and, thereby, on the pest and disease attack intensity. However, the relative importance of host composition effects on pest and disease intensity, due to resource dilution or amplification, and plant spatial structure effects, due to microclimatic alteration, is still unknown.Our objective was to quantify interactions between the composition and spatial structure characteristics of agroforests and the pest and disease attack intensity on a plot scale.This work was applied to cacao agroforests in Costa Rica and Cameroon. Indeed, cacao is one of the last crops still to be grown in traditional agroforests in the majority of producing countries. The study was conducted on two cacao diseases and one pest chosen for their contrasting spread and development characteristics: in Costa Rica, Frosty Pod Rot (FPR) intensity was studied in cacao agroforests in the Talamanca region; in Cameroon, Black Pod (BP) intensity and mirid density were studied in cacao agroforests in the Centre region.Firstly, we established shade tree spatial structure typologies for cacao agroforests in Costa Rica and Cameroon, in order to identify spatial structure diversity in the same region. A diversity of spatial structures was identified ranging from significant regularity to significant aggregation, depending on the shade tree stand and country studied.Secondly, we identified and classified the host composition, amount of sensitive tissue and the spatial structure characteristics of the associated plants, according to their explanatory power in explaining FPR intensity, BP intensity and mirid density in cacao agroforests. The spatial structure of the associated plants was a crucial characteristic of agroforests in explaining FPR and BP intensity and mirid density. Indeed, forest tree regularity decreased FPR intensity in Costa Rica and mirid density in Cameroon. The BP intensity was reduced by a decrease in the density of individuals belonging to strata lower than or equal to the cacao tree stratum. Lastly, the amount of sensitive tissue rather than the host composition variables explained the increase in FPR intensity in Costa Rica and the mirid density in Cameroon. Our results are discussed in line with several mechanisms that explain plant diversity and pest and disease relationships.Our work provides a precise description of complex tropical agroecosystem structures. We quantified the relationship between observed plant structures and the pest and disease regulation ecosystem service. In the context of agroecology, this work opens up prospects for identifying and understanding ecological mechanisms involved in natural pest and disease regulation in cacao agroforests on a plot scale
34
Lin, Wan-Ru, and 林宛儒. "A Monitoring and Forewarning System for Rice Pests." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/xr83py.
Full textAbstract:
碩士<br>國立交通大學<br>電子研究所<br>106<br>Planthopper is a kind of rice pest that travels from Philippines to Taiwan every year. These pests are able to polish off rice in a short time and spread quickly to a large area. Moreover, they carry some sort of disease that makes rice sick. When they travel from one place to another, the disease spreads along these areas and cause huge damage to the agricultural industry. For these reasons, it is urgent to construct a system that is capable of detecting rice pests in time.
Our detection model consists of two stages. At the first stage, traditional image processing technique conducts to detect the main part of the plant. We reserve this part and discard the remaining of the image. At the second stage, we use the convolutional neural network to detect pests. The model is based on the Single Shot Multi-box Detector which performs classification and localization at the same time. However, SSD has a serious problem for discarding too much background information at the max pooling layers. It is easy for the model to misrecognize reflected light as positive due to their similar shape and color. To solve this problem, we introduce a new way of pooling. Instead of reserving the max value, our model intends to save the local difference. This model can reserve more background information and obtain better results when evaluating.
35
Cheng, Yuan-Wei, and 鄭元瑋. "Image Recognition Technology of Rice Diseases and Insect Pests." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7bvuz6.
Full textAbstract:
碩士<br>國立中正大學<br>電機工程研究所<br>104<br>Rice is one of the most important agricultural products in ROC . In order to ensure the productivity of rice , the prevention and treatment of disease and pest is an important issue . Nowadays , the mainstream of rice cultivation is high density planting , witch make us hard to discover disease and pest of rice at the very first time . As a result , those plants with illness may infect other plants , and it will affect the total yield of rice . Therefore we design a recognition system based on image processing technology helping users recognize illness easily .
In our article , we first generalize the symptom of diseases and pest of rice . Then we choose leaf disease as the target , and analyze the key point of recognition of each illness with image . Therefore we may use some features to fit those points to recognize what illness occurred . In our research , one big difficulty is that there is no big and reliable database available from internet . It is hard for us to design a good algorithm from such a few samples . Overall , we propose a recognition system based on eight kind of symptoms , and we test our system with five kind of symptoms which include 150 pictures . Finally we get 84.67% matching rate for our testing .
36
Su, Yun-Kai, and 蘇筠凱. "A Monitoring and Forewarning System for Rice Pests via Multi-Scale Feature Mixture." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6w72tz.
Full textAbstract:
碩士<br>國立交通大學<br>電子研究所<br>107<br>Rice planthopper is a kind of global pest which can travel worldwide. They can survive in Taiwan even in winter and cause damage to the rice plant. In addition, some also spread disease that can cause immense loss in agriculture industry. Therefore, building a system that can detect rice planthoppers so that we can properly spray pesticide to minimize the damage is an important topic.
In this thesis, we develop a rice pest monitoring and forewarning system that can locate and count the number of pests. In the first phase, we use traditional image processing technique to detect the plant and ground. We reserve the major part of plant for the second phase process, which uses deep learning techniques to locate the pests and determine its species. Our model is based on Faster R-CNN and Feature Pyramid Network, which can handle multi-scale object detection. Feature pyramid network uses different resolutions to predict objects of different scales. We propose a Mixture block which combines multi-scale feature under the same resolution to provide better features for prediction. Additionally, we use negative data training strategy to handle hard negative. As a result, we obtain better results which contain fewer mistakes.
37
Yao, Nasser Kouadio. "A genetic study of resistance to African Rice Gall Midge in West African rice cultivars." Thesis, 2012. http://hdl.handle.net/10413/7989.
Full textAbstract:
The African Rice Gall Midge (AfRGM), Orseolia oryzivora Harris and Gagné (Diptera: Cecidomyiidae), is an endemic rice pest found throughout Africa. The failure of most other control methods imposes the need to use crop resistance. This study was initiated: (1) to develop an accurate method for assessing damage caused by AfRGM; (2) to determine AfRGM resistance genes’ modes of action, the heritability estimates of their resistance to AfRGM and the behavioural pattern of progenies with resistance to AfRGM attack; (3) to reveal convergent evolution of same or similar resistance gene(s) in geographically distinct landraces, or divergent evolution of genotypes carrying the same gene, by analysing the genetic diversity among five AfRGM parental lines; (4) to build a core sample of progenies to be used as a reduced mapping population, largely reflecting the entire genome of the whole population, after an estimate of the heritability of 15 agro-morphological descriptors and; (5) determine Simple Sequence Repeat (SSR) markers flanking genes or quantitative trait loci (QTLs) linked to resistance to AfRGM.
A method of accurately assessing damage caused by AfRGM was determined by comparing four methods of assessment including the International Rice Research Institute’s (IRRI) Standard Evaluation System (SES) for rice and three methods based on resistance index (RI) assessments differing in the computing of the percentage of tillers with galls on a resistant check variety. The RI-based assessment (RI-BA) methods consistently provided a better evaluation of AfRGM damage than the SES, regardless of the trial size. Within RI-BA methods, RI-BA2 was always more accurate than RI-BA1 and RI-BA3 when the plot was large. RI-BA2 and RI-BA3 were equally accurate when the plot size was small, and they provided better estimates than RI-BA1. When the plot was of medium size, RI-BA2 was more accurate than RI-BA3; RI-BA3 also surpassed RI-BA1. Overall, the best method of assessing AfRGM damage was RI-BA2, regardless of the plot size.
Five rice populations including F1, F2 and F3 generations involving ITA306, a susceptible variety of Oryza sativa subsp. indica, and four varieties having different reactions against AfRGM were used to determine the genetic basis of resistance and estimate the heritability of resistance to AfRGM. All the F1s were susceptible, suggesting recessive gene inheritance. The F2 generations’ segregation pattern of 1R:15S in both ITA306-TOS14519 and
ITA306-TOG7106 crosses as well as the segregation of 1R:8Seg:7S in ITA306-TOS7106 F3 families indicated that the AfRGM resistance expression being studied is governed by two genes. The deviation of the segregation patterns of crosses involving ITA306 and the tolerant parental lines from Mendelian segregation ratios suggests that the tolerance to AfRGM shown by BW348-1 and Cisadane is under complex mechanisms of control rather than under simple genetic control. The narrow-sense heritability estimates of resistance to AfRGM were low in populations involving tolerant varieties and were high in populations involving resistant varieties. They ranged from 0.086 in the ITA306-Cisadane population, to 0.4 in the ITA306-TOG7106 population. Conversely, the broad-sense heritability estimates ranged from 0.23 (ITA306-Cisadane) to 0.63 (ITA306-TOS14519).
The behavioural patterns of progenies against AfRGM attack were evaluated for 532, 413 and 479 F2 progenies from ITA306-BW348-1, ITA306-Cisadane and ITA306-TOS14519 crosses, respectively, in addition to 90 BC1F2 progenies from the ITA306 and TOG7106 cross. One F3 generation of 649 families from a cross between ITA306 and TOS14519 was also tested. Four types of behavioural pattern categories were observed: (1) progenies were more resistant than the resistant check entry at 45 DAT and 70 DAT; (2) progenies were more resistant at 45 DAT and became susceptible at 70 DAT; (3) progenies were susceptible at both 45 DAT and 70 DAT; (4) progenies were susceptible at 45 DAT but reverted to resistant at 70 DAT. The first three categories were the most frequently observed and occurred in all cross combinations. The last category was observed only for a few progenies from the ITA306-TOS14519 F2 and F3 generations and, surprisingly, many from the ITA306 and BW348-1 cross.
Heritability estimates were calculated for 15 major traits in an F3 population in order to predict the genetic gain associated with each trait, together with the resistance to AfRGM and to estimate the influence of the environment on phenotypic values. Broad-sense heritability (H2) estimates were high for the penultimate leaf length (PLL) - 0.99, penultimate leaf width (PLW) – 1.0, flag leaf length (FLL) - 0.99, flag leaf width (FLW) – 1.0, ligule length (LigL) - 0.99, tillering ability (Til) - 0.99, number of days to booting (DB) - 0.95, number of days to first heading (DFH) - 0.96, number of days to heading (DH) - 0.89, number of days to maturity (DM) - 0.98, culm length (CL) - 0.99, plant height (PH) - 0.99, panicle length (PanL) - 0.95, secondary branching (SB) - 0.95 and the thousand grains weight (TGW) - 0.71. Conversely,
narrow-sense heritability estimates were very low (nearly 0) in PLL, FLL, Lig, DB, DFH, DM and SB or low (at most 0.267) in PLW, FLW, DH and PH, with a high value of 0.727 for TGW. Inheritance of the traits studied was therefore under non-additive gene effects rather than additive genetic effects and can therefore be improved using pedigree breeding schemes along with breeding for AfRGM resistance.
Fine genetic evaluation of five AfRGM parental lines was studied in terms of polymorphisms using 303 SSR primers covering the rice genome. Of the 178 polymorphic primers identified, 60 were highly polymorphic and informative. The number of alleles amplified by these primers ranged from one to five for a total of 1,041 alleles. The polymorphism rate was globally high, ranging from 45.2% to 66.8%. The mean of the polymorphism information content (PIC) was 0.553. Factorial analysis, based on the allelic diversity, demarcated the parental lines into Oryza glaberrima Steud, Oryza sativa subsp. japonica and O. sativa subsp. indica groups, while a cluster analysis distinguished them into four groups: AfRGM resistant, susceptible, moderately resistant and tolerant. BW348-1 and Cisadane showed the least diversity, despite their distant geographical origins. TOS14519 and TOG7106 showed more divergence to ITA306 despite their common West African origin. This variability amongst the genotypes tested is the result of farmer-based selection for AfRGM resistance rather than direct breeding efforts through breeder intervention.
A method of selecting individuals for a mapping population, based on a core sample, was developed in order to speed up the mapping procedure. A diversity study amongst F2 and F3 generations involving 15 quantitative and 26 qualitative agro-morphological characters was carried out and led to the dropping of seven non-discriminant descriptors. The diversity index (H) was calculated for each remaining character and the discriminant descriptors were selected based on a diversity index threshold value above 0.4. Four descriptors of H values less than 0.35 were therefore dropped. The sizing of the core collection of 64 individuals and the selection of these individuals were done using MSTRAT version 4.1 package in redundancy mode, a construction run of 100 times with an iteration number of 500. The core sample was similar to the whole population for clustering pattern, minimum and maximum quantitative values and diversity index, while mean values and coefficient of variation distinguished them. The core sample, which represents 10% of the whole population, also revealed the same phenotypic variation and the same genotypic segregation according to two SSR markers. It can therefore efficiently reflect the whole population as a mapping population.
Finally, a study was undertaken to identify flanking markers to the gene/QTL involved in the resistance against AfRGM using bulked segregant analysis (BSA). A polymorphism study between ITA306 and TOS14519 displayed 145 polymorphic SSR markers, which were used to screen the bulks that originated from the two tails, and depicted only two SSRs as candidate markers linked to gall midge resistance. These markers included RM317 and RM17303 which displayed strong significance after an analysis of variance using an F test, meaning that they were segregating with the resistant alleles.<br>Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
38
Rehman, Faiz-Ur. "Serological and pathological evaluations of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice." Thesis, 1995. http://hdl.handle.net/10125/9463.
Full text
39
Ge, Wen-Zun, and 葛文俊. "Vertical distributions, Seasonal population changes and post-fumigation reinfestation of insect pests in stored rice." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/97113403986663504200.
Full text
40
Sow, Mounirou El-Hassimi. "Genetic diversity of Oryza species in Niger ; screening and breeding for resistance to rice yellow mottle virus (RYMV)." Thesis, 2012. http://hdl.handle.net/10413/8520.
Full textAbstract:
Rice is a staple food in many West African countries, including Niger. However, both regional and national rice production have failed to meet demand due to several constraints, among which is the Rice yellow mottle virus (RYMV). Moreover, attempted intensification of rice cultivation and the introduction of modern cultivars are encouraging farmers towards abandoning local landraces for high yielding, but often susceptible varieties. The study was primarily oriented towards rice pre-breeding, and identifying priorities for rice breeding in Niger in relation to farmers' preferences and their environment. A secondary aim was the development and evaluation (for release at the regional level) of new breeding lines with resistance to RYMV. This study aimed to: 1) Establish farmers' perception of rice varieties as well as the main constraints on rice production in Niger and particularly those posed by RYMV; 2) Create a collection of rice species from Niger for ex- situ conservation, and to determine the phenotypic variability within this collection; 3) Determine the genetic diversity and population structure of the collection; 4) Screen the collection for resistance to RYMV, so that new sources of resistance could be detected; 5) Improve five elite varieties from West Africa for resistance to RYMV using marker-assisted selection (MAS). The germplasm collection and PRA of this study were conducted in 2008 and 2009 in Niger, while the field and the laboratory researches were conducted in 2008 and 2009 at the Africa Rice Center (AfricaRice) in Benin. For the PRA, data was obtained from a semi-structured group discussion carried out in 14 villages, individual questioning of 153 farmers and visits to farmers' field and storage facilities. The local farmers' union was the only formal seed dissemination system. Seed exchanges between farmers and the use of seeds from previous harvests were important. The RYMV and the bacterial leaf blight (BLB) were cited as the prevalent biotic stresses in the irrigated agrosystem, where the varieties IR1529-680-3 and Waihidjo were found to be the most popular. Flood, birds and hippopotamus were the most damaging agents in the lowland cropping system, and the landrace Degaulle/ D5237 was the preferred variety. Apart from the yield, farmers preferred varieties with good grain quality (milling quality and good taste), high market value, stress tolerance (drought, flood, disease, birds, rodents), and those recommended by the local farmers' association. These findings should be included in breeding goals, seed production and dissemination systems. During collection, a total of 270 rice accessions were assembled, comprising the two cultivated rice species Oryza sativa L. and O. glaberrima Steud. and its two wild relatives Oryza barthii A. Chev. and O. longistaminata Chev. et Roehr. The region of the Niger River and its tributary (the Dallol Maouri) provided the majority (80.7%) of the accessions. Apart from a few wild O. barthii accessions, the accessions found around Lake Chad and the Komadougou river (South-East) were also collected in the Niger River area. Farmers' naming and ecological classification of rice varieties was generally consistent. Three major phenotypic groups were found during the field trials, and the overall phenotypic variability of the collection (as measured by the Shannon-Weaver Diversity Index) was relatively high. There was no significant difference in diversity between the main eco-geographical zones of collection, as well as between the identified phenotypic groups, suggesting a high level of germplasm exchange between the regions in Niger.
From the collection, 264 accessions were genotyped from the collection using 18 well distributed SSR markers and two main genetic compartments were detected, comprising O. sativa subsp. indica varieties and O. glaberrima and its wild relative O. barthii and O. longistaminata. The O. sativa group in Niger was divided into irrigated and floating rice, bound by lowland rice. The wild progenitor O. barthii was widespread but without any clear genetic differentiation from O. glaberrima, probably due to the presence of admixtures within the collected samples of O. barthii. Allelic diversity was relatively high, despite the geographical distance from the centre of domestication of African rice, and the points of entry of Asian rice to Africa. The findings reflect the underuse of Niger's rice landraces genetic potential for rice breeding, given that all the "improved" varieties released during the last 25 years in Niger were clustered together on the dendrogram. The response of a set of the rice collected from Niger and some accessions from Mali to inoculation by RYMV was evaluated using five different virus isolates from Niger (3), Benin (1) and Burkina Faso (1). All rice varieties were susceptible to the disease. However, depending on the virus strain, a few O. glaberrima accessions displayed partial resistance, similar to the highly resistant TOG5681. Allelic research based on primers derived from the RYMV1 gene revealed one accession with allele rymv1-3, and two accessions with allele rymv1-4, and one accession with a different resistance gene. The implications of the finding were discussed and a strategy proposed for breeding varieties with a comprehensive resistance to RYMV.
After three generations of backcrossing, the major resistance gene of the variety Gigante was successfully introgressed into five elite rice varieties of West Africa by Marker-Assisted Backcross (MABC). The newly developed BC3F3 progenies were screened for resistance to RYMV in farmers' fields in Guinea and Mali and also under controlled conditions in a screenhouse in Benin. As shown by low virus content and level of disease incidence, low tiller number and plant height reduction, the transferred gene was fully functional in the new genetic background. Moreover, some lines also displayed a high level of resistance to rice blast (Pyricularia oryzae) and stem borer infestation in Guinea. Four of those lines are in the second year of multi-location trial in seven West African countries. Therefore, effective deployment of the newly developed varieties, coupled with good cultural practices, should reduce the damaging effects of RYMV in lowland and irrigated rice cropping systems and thereby increase the income of small scale farmers from rice cultivation.<br>Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
41
"The potential role and mechanism of an unconventional GTPase and its interacting partner in rice defense response." 2009. http://library.cuhk.edu.hk/record=b5894091.
Full textAbstract:
Xue, Yan.<br>Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.<br>Includes bibliographical references (leaves 95-102).<br>Abstract also in Chinese.<br>Thesis committe --- p.2<br>Statement --- p.3<br>Abstract --- p.4<br>Acknowledgement --- p.8<br>General abbreviations --- p.10<br>Abbreviations of chemicals --- p.13<br>List of figures --- p.15<br>List of tables --- p.16<br>Table of contents --- p.17<br>Chapter Chapter 1 --- General Introduction<br>Chapter 1.1 --- Impact of bacterial blight on rice production --- p.25<br>Chapter 1.2 --- The plant immune system --- p.25<br>Chapter 1.2.1 --- Preformed resistance --- p.25<br>Chapter 1.2.2 --- PAMP triggered immunity (PTI) --- p.26<br>Chapter 1.2.3 --- Effecter triggered immunity (ETI) --- p.27<br>Chapter 1.2.3.1 --- R genes --- p.27<br>Chapter 1.2.3.2 --- Hypersensitive responses (HR) --- p.27<br>Chapter 1.2.3.3 --- Systemic acquired resistance (SAR) --- p.28<br>Chapter 1.2.3.3.1 --- Salicylic acid is required for SAR establishment --- p.28<br>Chapter 1.2.3.3.2 --- Involvement of lipid-based molecules in SAR signaling --- p.28<br>Chapter 1.2.3.3.3 --- NPR1: the master regulator of SAR --- p.29<br>Chapter 1.2.3.3.4 --- Expression of pathogenesis related (PR) genes --- p.29<br>Chapter 1.2.4 --- Interaction between SA and JA --- p.29<br>Chapter 1.2.5 --- Other important signaling components in plant defense responses --- p.30<br>Chapter 1.2.5.1 --- G proteins --- p.30<br>Chapter 1.2.5.2 --- G proteins in defense responses --- p.30<br>Chapter 1.3 --- OsGAPl is a C2 (protein kinase C conserved region 2) domain harboring GTPase activating protein --- p.32<br>Chapter 1.4 --- OsYchFl is a GTPase and an interacting partner of OsGAPl --- p.32<br>Chapter 1.5 --- Hypothesis and objectives of this research --- p.33<br>Chapter Chapter 2 --- materials and methods<br>Chapter 2.1 --- Materials --- p.35<br>Chapter 2.1.1 --- Chemicals and reagents --- p.39<br>Chapter 2.1.2 --- Commercial kits --- p.40<br>Chapter 2.1.3 --- Primers used --- p.41<br>Chapter 2.1.4 --- Equipment and facilities used: --- p.47<br>Chapter 2.1.5 --- "Buffer, solution, gel and medium:" --- p.47<br>Chapter 2.2 --- Methods: --- p.51<br>Chapter 2.2.1 --- Culture of bacterial strains --- p.51<br>Chapter 2.2.2 --- Composition of medium used in this work for cultivating bacterial strains: --- p.51<br>Chapter 2.2.3 --- Plant growth and treatment --- p.52<br>Chapter 2.2.3.1 --- Surface sterilization of Arabidopsis thaliana seeds --- p.52<br>Chapter 2.2.3.2 --- Seed germination and Arabidopsis plant growth --- p.52<br>Chapter 2.2.4 --- Generation of transgenic Arabidopsis --- p.53<br>Chapter 2.2.4.1 --- Agrobacterium-mediated Arabidopsis transformation --- p.53<br>Chapter 2.2.5 --- Pathogen inoculation test --- p.54<br>Chapter 2.2.6 --- Molecular cloning --- p.54<br>Chapter 2.2.6.1 --- DNA sequencing: --- p.55<br>Chapter 2.2.6.2 --- Transformation of E. coli strains: --- p.55<br>Chapter 2.2.6.3 --- Transformation of Agrobacteria by electroporation --- p.55<br>Chapter 2.2.7 --- DNA and RNA extraction --- p.56<br>Chapter 2.2.7.1 --- Plasmid DNA extraction from bacterial cells --- p.56<br>Chapter 2.2.7.2 --- Genomic DNA extraction from plant tissues --- p.56<br>Chapter 2.2.7.3 --- RNA extraction from plant tissues --- p.56<br>Chapter 2.2.8 --- Northern blot --- p.57<br>Chapter 2.2.9 --- Subcellular localization studies --- p.58<br>Chapter 2.2.9.1 --- Transformation of tobacco BY-2 cells --- p.58<br>Chapter 2.2.9.2 --- Maintenance of transgenic tobacco BY-2 cells --- p.59<br>Chapter 2.2.9.3 --- Confocal microscopy --- p.59<br>Chapter 2.2.9.4 --- Electron microscopy --- p.59<br>Chapter 2.2.10 --- Bimolecular fluorescence complementation studies (BiFC) --- p.60<br>Chapter 2.2.10.1 --- Construct making --- p.61<br>Chapter 2.2.10.2 --- Preparation of rice protoplasts --- p.61<br>Chapter 2.2.10.3 --- PEG-mediated transfection --- p.62<br>Chapter 2.2.10.4 --- Detection of protein-protein interaction --- p.62<br>Chapter Chapter 3 --- Results<br>Chapter 3.1 --- OsGAPl interacts with OsYchFl in vivo --- p.63<br>Chapter 3.1.1 --- Construction of vectors for BiFC transient assay in rice protoplasts --- p.64<br>Chapter 3.1.2 --- BiFC assay in rice protoplasts revealed in vivo interaction between the OsGAPl and the OsYchFl proteins --- p.66<br>Chapter 3.2.1 --- Subcellular localization of OsGAPl --- p.68<br>Chapter 3.2.2 --- Localization of OsGAPl and OsYchFl in rice leaves revealed by electron microscopy --- p.70<br>Chapter 3.3 --- Functional characterization of OsYchFl<br>Chapter 3.3.1 --- Characterization of Arabidopsis YchF1 knockdown mutant --- p.75<br>Chapter 3.3.2 --- Complementation of AtYchF1 knockdown Arabidopsis --- p.77<br>Chapter 3.3.3.1 --- Pathogen inoculation test --- p.80<br>Chapter Chapter 4 --- Discussion<br>Chapter 4.1 --- Significance of the project --- p.85<br>Chapter 4.2 --- In vivo interaction between OsGAPl and OsYchFl --- p.86<br>Chapter 4.3 --- OsGAPl is located either inside the cytosol or on the plasma membrane in transgenic tobacco BY-2 cells --- p.87<br>Chapter 4.4 --- Study of wounding effect on the subcellular localization of OsGAPl and OsYchFl at whole plant level by EM --- p.88<br>Chapter 4.5 --- OsYchFl functions as a negative regulator of defense responses in A.thaliana --- p.90<br>Chapter 4.6 --- Conclusion --- p.92<br>References --- p.95<br>Appendix --- p.103
42
Kam, Honore. "A study of the diversity of Burkina Faso rice landraces and identification of source of resistance to rice yellow mottle virus (RYMV)." Thesis, 2011. http://hdl.handle.net/10413/8518.
Full textAbstract:
The main goals of this study were to ascertain farmers' preferred traits in rice landraces and their perception of Rice yellow mottle virus, to collect rice landraces across Burkina Faso, investigate their genetic diversity, and to exploit this diversity in a search for varieties resistant and tolerant to RYMV, for their utilisation in rice breeding. Farmers' preferred traits, approaches to crop management, and disease perceptions were assessed using a Participatory Research Appraisal (PRA) approach. In the main rice growing regions of Burkina Faso, 330 rice landraces were collected. The agro-morphological diversity of the germplasms was evaluated in the field with 20 quantitative and 30 qualitative agro-morphological parameters. Thereafter, 22 Simple Sequence Repeat molecular markers were used to assess the genetic diversity and the population structure of the collection. Finally, the rice landraces were screened against four RYMV isolates to assess the susceptibility, tolerance and resistance of the landraces in the collection using visual assessment and Enzyme Linked Immunosorbent Assay. The PRA identified sweet taste, grain expansion when cooking, easy cooking and yield as paramount selection criteria in rural rice farming communities in Burkina Faso. Drought and disease resistance are characters that farmers wish to have in their varieties. The PRA also highlighted that farmers are conscious of RYMV disease in their fields. However, they are unaware about the epidemiology of the disease.
An agro-morphological study of the phenotypic diversity of the collection confirmed the presence of the two cultivated rice species: O. glaberrima and O. sativa. There were more O. sativa accessions than O. glaberrima landraces. There were 48 O. glaberrima and 282 O. sativa accessions in the collection. Both species were divided into four clusters, reflecting the richness of the collection. The underlying genetic diversity of the collection was confirmed by the use of 22 Simple Sequence Repeat molecular markers. The neutral markers confirmed the existence of two substructures, namely O. glaberrima and O. sativa, and the presence of admixture varieties. However, a core collection of 52 individuals was developed. This included 13 O. glaberrima and 39 O. sativa accessions. It reflects the genetic diversity of the sub-clusters present in each species. This core collection contains 89% of the allelic richness of the collection. Its small size will facilitate the maintenance and active use of diversity of germplasm in the core collection. The entire collection was utilised to search for varieties resistant and tolerant to RYMV disease. The screening of the collection with different RYMV isolates exposed the susceptibility of most of the accessions in the collection. Most of the O. sativa indica accessions were highly susceptible. However, ten O. glaberrima accessions displayed a delay of symptom expression, and moderate resistance. However, their resistance was overcome later by a particularly virulent RYMV isolate BF1. Remarkably, a single moderately resistant cultivar, BM24, showed that partial resistance and tolerance to RYMV can be found in an O. sativa variety. Serological evaluation of this local variety in comparison with the partially resistant variety, Azucena, showed that BM24 and Azucena expressed similar resistance patterns. A genetic profile of both varieties showed that both had an identical allele status at RM101, which is a marker bracketed in the same zone as the QTL12.<br>Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
43
Hossain, Mohammed Tufazzal. "Studies of the impact of mycoflora associated with oryza sativa (rice) in South Africa." Thesis, 2014. http://hdl.handle.net/10500/13266.
Full textAbstract:
The objective of this research was to investigate the occurrence of mycoflora in rice plants and rice seeds in South Africa and their negative impact.
A total of six species of Fusarium were isolated from diseased rice plants and rice seeds and identified as F. anthophilum, F. chlamydosporum, F. compactum, F. equiseti, F. fujikuroi and F. semitectum. In the translation elongation factor data set, Fusarium equiseti isolates grouped together within the F. incarnatum - equiseti Species Complex (FIESC). The isolates from rice clustered together in a single clade with the F. equiseti and F. incarnatum isolates forming two separate sub-clades.The isolates of F. equiseti present a new phylogenetically distinct species in FIESC.
In the pathogenicity tests, isolates of both F. anthophilum and F. fujikuroi caused bakanae disease to rice plants. Fifty four rice cultivars and lines were tested by the standardized test tube inoculation method for resistance and susceptibility against bakanae isolate of F. anthophilum and the bakanae isolate of F. fujikuroi. None of the rice cultivars and lines was found to be resistant to bakanae isolates of Fusarium spp.
The fungicide, benomyl was found to be most effective as a seed treatment for controlling bakanae disease of rice due to isolates of both F. anthophilum and F. fujikuroi. Thiram was found to be the least effective fungicide for controlling bakanae disease of rice caused by isolates of both the Fusarium spp.
Apart from Fusarium species, other fungi that were also isolated from diseased rice plants and rice seeds were identified as Alternaria alternata, Alternaria longipes, Cochliobolus miyabeanus, Nigrospora sphaerica, Phoma eupyrena, Phoma jolyana, Phoma sorghina and Pithomyces sp. In mycotoxin tests, the isolates of both F. anthophilum and F. fujikuroi produced moniliformin. None of the isolates of F. anthophilum and F. fujikuroi produced fumonisins.
This research is important as it identifies many fungal species in rice plants and seeds in South Africa for the first time. Currently, there is very little literature that makes reference to such findings under South African conditions. In addition, this investigation unravels previously unknown information on the resistance of rice to bakanese disease. Finally, information is provided on the effectiveness of commonly used fungicides (benomyl and thiram) to control rice diseases. This knowledge is crucial information that is useful to plant pathologists, the farming community and the scientists that are involved in strategies of fighting or reducing rice diseases so as to help contribute to food security.<br>Environmental Sciences<br>D. Phil. (Environmental Science)
44
Chambers, Craig Brian. "Development of fungal biological control of four agriculturally important pests, Sitophilus oryzae, Trialeurodes vaporariorum, Planococcus ficus and Eldana saccharina, in South Africa." Thesis, 2005. http://hdl.handle.net/10413/4062.
Full textAbstract:
The use of entomopathogenic fungi to control agriculturally important pests, both in
greenhouses and in the field, has been demonstrated by various authors for a number of
years. This has been brought about by the development of resistance in certain pest
species to chemical applications and a growing public awareness of the safety
implications of residual insecticides. Several entomopathogenic fungi were tested
against four insect pests found in the Republic of South Africa (RSA), the greenhouse
whitefly, Trialeurodes vaporariorum, the rice weevil, Sitophilus oryzae, the grapevine
mealybug, Planococcusficus and the sugarcane stem borer, Eldana saccharina. Further
concentration, temperature and humidity studies were conducted with selected isolates
on the rice weevil, S. oryzae.
Sitophilus oryzae is considered one ofthe most important pests of stored grain. Several
fungal isolates were tested against the rice weevil, four of which, B1, PPRI 6690, PPRI
6864 and PPRI 7067, were selected for further testing based on the mortality results over
a 21 d period. Varying conidial concentrations were applied and at high doses of 1x10 -6
conidia ml -1 with mortality rates of to 84% achieved. LT 50 values ranged from 6 - 68d.
Increased spore concentration resulted in an increase in overall mortality.
Temperature and humidity was found to affect the infection potential of the four isolates
tested. Four temperatures ranging from 15 - 30°C were tested. The highest mortality
rates were obtained at 25°C where mortality ranged from 46 - 65% in 14d. Mortality
rates decreased with decreasing temperature, and no mortality was recorded at 30°C.
Temperature was found to significantly alter the LT 50 values, increasing the LT 50 with
decreasing temperatures. Decreasing the humidity resulted in an increased LT 50 and a
reduction in the overall mortality rates. The mortality of S. oryzae ranged according to
the RH and isolate. Isolates Bland PPRI 6690 resulted in the highest mortalities of 80
and 83% at 92.5% RH, with LT 50's of 6.3d and 6.4d, respectively.
Several entomopathogenic fungi were tested against T vaporariorum, P. ficus and E.
saccharina, three key pests of South African crops. Nine fungal isolates were tested
against the greenhouse whitefly, T vaporariorum, with mortalities ranging from 26.7 - 74.7% over 14d. Beauveria bassiana Isolates Bl and PPRl 6690 produced the highest
mortality rates and were recommended for further pathogenicity testing against T.
vaporariorum.
Planococcus ficus is a common pest ofvineyards in the Western Cape Province, South
Africa. Nine entomopathogenic fungi were screened against P.ficus, only two of which
produced mortality. Eldana saccharina is a stalk borer, which infests sugarcane in large
areas of Southern Africa. Five isolates were tested against second and third instar larvae,
three of which, B1, PPRl 6864 and PPRl 6690 resulted in mortalities. Mean percentage
mortality was low for all three isolates.
From the study it was evident that two of the isolates tested, Bland PPRI 6690 (B.
bassiana), showed potential against three of the four pests, and two isolates of
Lecanicillium lecanii caused mortality in P. ficus. Further research and understanding of
the effect of environmental conditions, spore concentration and epizootic potential
would result in the further development of these isolates as future biological control
agents.<br>Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
45
Yahya, Husnawati, and Husnawati Yahya. "Review of Taiwanese and Indonesian Rice Planting Methods and Insect Pest Management." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/67446558506391774968.
Full textAbstract:
碩士<br>國立東華大學<br>自然資源與環境學系<br>101<br>Every country has developed rice planting methods and insect pest management. Rice planting methods and pest management strategies in Taiwan and Indonesia was reviewed to gather current information concerning rice planting methods and development of sustainable management strategies. By optimizing these aspects, farmers can obtain optimal production of their crop. Interviews and website reviews are the methods used to get more information about rice farming and pest management in both countries. Taiwan has developed superior rice varieties in different counties. Using natural fertilizers and organic fertilizers are commonly applied by Taiwanese rice farmers. The benefit of organic fertilizer is to provide nitrogen, phosphate, and potassium as naturally without using urea, ammonium sulfate, or super phosphate as chemical fertilizer. Interview results showed that there were no greatly differences between rice planting methods in Indonesia and Taiwan. Both countries use transplanting method for rice planting. Tractors are commonly used for land preparation. Integrated crop management is the common method that applied by Indonesian farmers. Using superior rice varieties that resistant to the pest is one concept of integrated crop management. Natural fertilizers and organic pesticides are the way for reducing chemical residues in ecosystems. Using chemical fertilizer is the last choice for controlling pest population. Reviewed agriculture websites in both countries shows that many information about chemical pesticides, especially registered chemical pesticides by council of agriculture. The limitation of this study is on study sites. The numbers of study sites of both countries are around six study sites. By searching agriculture websites, the general information of rice planting methods and insect pest management in Taiwan and Indonesia can be solved and described. Transition agriculture from conventional to organic is a program that still continues in Taiwan and Indonesia. Cultural control is the best pest management in the future. The goals of applying superior rice varieties (by rice breeding) and transition from conventional to organic are for increasing rice quality and quantity and keeping environmental balances.
46
"A novel simple extracellular leucine-rich repeat (eLRR) domain protein from rice (OsLRR1) enters the endosomal pathway and interacts with the hypersensitive induced reaction protein 1 (OsHIR1)." Thesis, 2009. http://library.cuhk.edu.hk/record=b6074981.
Full textAbstract:
Receptor-like protein kinases (RLKs) containing an extracellular leucine-rich-repeat (eLRR) domain, a transmembrane domain, and a cytoplasmic kinase domain play important roles in plant disease resistance. Simple eLRR domain proteins structurally resembling the extracellular portion of the RLKs may also participate in signaling transduction and plant defense response. Yet the molecular mechanisms and subcellular localization in regulating plant disease resistance of these simple eLRR domain proteins are still largely unclear. We provided the first experimental evidence to demonstrate the endosomal localization and trafficking of a novel simple eLRR domain protein (OsLRR1) in the endosomal pathway, using both confocal and electron microscopy. Yeast 2-hybrid and in vitro pull-down assays show that OsLRR1 interacts with the rice hypersensitive induced response protein 1 (OsHIR1) which is localized on plasma membrane. The interaction between LRR1 and HIR1 homologs was shown to be highly conserved among different plant species, suggesting a close functional relationship between the two proteins. The function of OsLRR1 in plant defense response was examined by gain-of-function tests using transgenic Arabidopsis thaliana. The protective effects of OsLRR1 against bacterial pathogen infection were shown by the alleviating of disease symptoms, lowering of pathogen titers, and higher expression of defense marker genes.<br>Zhou, Liang.<br>Adviser: Hon Ming Lam.<br>Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: .<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2009.<br>Includes bibliographical references (leaves 90-107).<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Abstract also in Chinese.
47
Chiu, Yi-Chia, and 邱怡嘉. "Functional Annotation of Rice Expressed Sequence Tag Induced by Important Disease and Pest." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/6z25qv.
Full textAbstract:
碩士<br>朝陽科技大學<br>生物技術研究所<br>94<br>Abstract
Rice (Oryza sativa L.) is the most important crop in the world. Brown planthopper is the major pest so is the rice blast disease the most serious problem. Expressed sequence tag (EST) is the fragment of cDNA sequence. Therefore, direct studies of EST is helpful to obtain the gene expression information. In order to know the functional mechanisms of the resistant gene which cause the brown planthopper and rice blast, this study firstly accessed rice EST sequences induced by brown planthopper from NCBI-dbEST database (with the total amounts as 188), and compared the gene expression difference between the resistant and sensitive varieties of rice. An analytic procedure of rice EST functional annotation was established as: Firstly, using unique sequences of high quality from removing redundancy after clustering and assembling by CAP3 software to homology search TC(tentative consensus sequence) database of TIGR (The Institute of Genomic Research), then linking to the functional catalogs of GO (Gene Ontology) and MIPS (Munich Information Center for Protein Sequences) from tentative annotation of the selected TC sequences, and finally calculating the statistics of gene functional representation. Based on this procedure, an automated system of functional annotation was developed. All programs of this system were written in perl language under local Linux platform. The automated system was implemented in the huge amount of rice ESTs induced by M. grisea (with the total amounts as 84,705) to investigate the gene expression differences among different varieties, tissues and developmental stages of rice. The results showed that (1) based on GO functional category, biological process was the dominant gene function of rice ESTs induced by brown planthopper. According to minute classification of MIPS functional category system, the genes of resistant rice variety expressed richer metabolism function than that of sensitive rice variety. The resistant rice variety switched on the functions related to cell rescue/defense and virulence, transcription, and cell growth/morphogenesis, but sensitive variety did not. (2) When rice ESTs induced by M. grisea were mixtures of sequences with different varieties, tissues or developmental stages, it appeared diversity of gene expression from those of rice ESTs from single source. The genes of wild rice expressed richer metabolism function than those of Indian rice and Japanese rice. The findings of this study will help clarify the mechanisms of rice genes resistant to disease and pest.
48
Li, Zhongyi. "Molecular analysis of genome segment 5 of rice ragged stunt virus and transformation of Indica rice with segment 5 based genes." Phd thesis, 1996. http://hdl.handle.net/1885/144402.
Full text
49
"Comparative analysis of disease resistance related genes in rice." 2004. http://library.cuhk.edu.hk/record=b6073736.
Full textAbstract:
by Zeng Naiyan.<br>"December 2004."<br>Thesis (Ph.D.)--Chinese University of Hong Kong, 2004.<br>Includes bibliographical references (p. 185-213)<br>Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.<br>Mode of access: World Wide Web.<br>Abstracts in English and Chinese.
50
Collins, Nicholas Charles. "The genetics of barley yellow dwarf virus resistance in barley and rice." Thesis, 1996. http://hdl.handle.net/2440/46063.
Full textAbstract:
Barley yellow dwarf virus (BYDV), an aphid transmitted luteovirus, is the most widespread and economically damaging virus of cereal crops. The work in this thesis aims to characterise the basis of the naturally occurring resistance to BYDV in cereals in three ways: Firstly, by facilitating the isolation of the Yd2 gene for BYDV resistance from barley by a map-based approach. Secondly, by determining if a BYDV resistance gene in rice is orthologous to Yd2. Thirdly, by establishing if other BYDV resistance genes in non- Ethiopian barleys are allelic to Yd2. It is hoped that the information generated in this study will ultimately assist in the production of BYDV resistant cereal cultivars.
A detailed genetic map of the Yd2 region of barley chromosome 3 was constructed, containing 19 RFLP loci, the centromere and the Yd2 gene. Yd2 mapped on the long arm, 0.5 cM from the centromere, and in the mapping population of 106 F2 individuals, perfectly cosegregated with the RFLP loci XYlp, and Xwg889. This map represents the first stage in a project to isolate the Yd2 gene by a map-based approach. The isolation of Yd2 could help to elucidate the molecular mechanism of the Yd2-mediated BYDV resistance, and may allow the production of BYDV resistant cereals by genetic transformation. The RFLP markers mapped closest to Yd2 could also be useful in barley breeding, by enabling selection for both the presence of Yd2 and the absence of agronomically undesirable traits known to be closely linked to Yd2.
Genetically Directed Representational Difference Analysis (GDRDA) is a technique based on subtractive hybridisation, which can be used to identify RFLP markers closely linked to a gene of interest. Two GDRDA experiments were performed with the intention of generating additional RFLP markers close to Yd2. However, the first experiment yielded RFLP probes that were not derived from the barley genome, while the second experiment yielded probes that detected repetitive sequences. It was concluded that GDRDA is of limited use in generating further markers close to Yd2.
To isolate the Yd2 gene by a map-based approach, a much larger mapping population will need to be analysed to genetically resolve markers tightly linked to Yd2. If the two morphological markers uzu dwarf and white stripe,,j flank Yd2, then they could assist in this task by enabling the visual identification of F2 seedlings resulting from recombination close to Yd2. However, in this study, both morphological markers were found to be located distal to Yd2. Therefore, these two morphological markers can not be used together to facilitate high resolution genetic mapping of the Yd2 locus.
It may be possible to use large-insert genomic DNA clones from the relatively small genome of rice to generate further RFLP markers close to the Yd2 gene in barley, provided that the order of orthologous sequences in barley and rice is conserved close to the Yd2 locus. To assess the feasibility of this approach, RFLP probes used to identify loci close to Yd2 were mapped in rice using a segregating rice F2 population. Five of the RFLP loci mapped together and in the same order as RFLP loci mapped close to Yd2 in barley using the same probes. By comparing the location of RFLPs mapped by other researchers in rice using probes mapped close to Yd2, the region of conserved linkage between rice and the Yd2 region was tentatively identified as the central portion of rice chromosome 1. The collinearity shown by orthologous sequences in barley and rice indicated that it may indeed be possible to use rice to assist in generating RFLP markers close to Yd2.
Of all the cereals, rice is the most amenable to map-based gene isolation, due to its small genome, well developed physical and genetic maps, and its ability to be genetically transformed with high efficiency. If a BYDV resistance gene that is orthologous to Yd2 could be identified in rice, this gene could be isolated with relative ease, and then used to identify barley cDNA clones corresponding to Yd2 gene by virtue of the sequence homology expected between these genes. To test if a BYDV resistance gene from an Italian rice line is orthologous to Yd2, recombinant-inbred rice lines previously characterised for this gene were analysed using probes mapped close to Yd2 in barley. No genetic linkage was detected between the RFLP loci and the BYDV resistance gene, indicating that the gene is unlikely to be orthologous to Yd2.
BYDV resistance alleles at the Yd2 locus which are of a non-Ethiopian origin may show interesting differences to Ethiopian Yd2 resistance alleles. To identify barleys which may contain resistance alleles of Yd2, ten BYDV resistant barleys not known to contain Yd2 were assessed for their resistance to the PAVadel isolate of BYDV in the glasshouse. CI 1179, Rojo, Perry, Hannchen, Post and CI 4228 were found to be the most resistant under these conditions, and were analysed further. If the resistance from these barleys is controlled by alleles of Yd2, RFLP markers close to Yd2 will be expected to cosegregate with the resistance in F2 families derived from crosses between these resistant barleys and the BYDV susceptible barleys Atlas and Proctor. RFLPs suitable for use in these allelism tests were identified using probes mapped close to Yd2. However, time did not permit the analysis of these F2 populations.<br>Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Science, 1996