Tesis sobre el tema "Pyricularia grisea"

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Wheat (Triticum spp.) is a grass grown and used as an energy source worldwide being cultivated in several regions of Brazil. However, some diseases severity and ineffective chemical control have been threatening Brazilian wheat production. Among the diseases, the blast of wheat caused by the fungus Pyricularia grisea, is gaining a prominent role, being able to reduce crop yields by up to 70%. Chemical control of the disease has been unsatisfactory and there is little information on genetic resistance available in the literature. Resistance is the best way to control diseases by both economically and environmentally advantages. Given these facts, the objective of this study was to evaluate the resistance to blast of wheat genotypes for later use in breeding programs. It was obtained 10 different isolates of the cereal producing regions in Brazil. The isolates were transferred to PDA medium (potato dextrose agar) and after development and cleansing of the colonies were transferred to OA medium (oatmeal and agar) and maintained at a temperature of about 25 ° C and light regime of 12 hours for 10 days for sporulation of the fungus to occur. The concentration of the fungus used in the inoculations was adjusted to 1.2 x 105 spores / mL. In the first experiment, plants were inoculated when they had four leaves. The plants were kept under controlled conditions at 25° C and evaluated seven days after inoculation. Plants were classified according to the type of infection and later was calculated the Resistance Spectrum Relative (RSR) (percentage of isolates that the genotype expressed resistance) and the Disease Index (DI) (resistance of a genotype using all range of types of infection). The DI values were considered different (p≤0,05) if their confidence intervals (95%) did not overlap. Genotypes IVI 04033, VI 07443, VI 07505, IVI 04028, VI 07157, VI 04026, VI 98053 and VI 07160 were susceptible to more than 80% of isolates. Five varieties and four lines had a RSR greater than 50% and DIs smaller than 0.6. Among the lines stood out VI 04098 and VI 07094 with RSR greater than 80%, equating to the variety IPR 85. In the second experiment conducted under field conditions, inoculation was done staggered, according to the cycle of the genotypes, when plants reached the stage of 58-60 in Zadoks scale (1974), being applied 1L of suspension of P. grisea at a concentration of 1.2 x 105/mL per plot. Productivity was assessed by harvesting each plot area (3 m2). Disease incidence was assessed by the percentage of infected spikes and severity was assessed by the percentage of infected spikelets in each spike.The yield ranged from 879 to 3983 kg / ha, the incidence of the disease ranged from 0.86 to 84.24% and the severity ranged from 0.48 to 65.29%. Seven genotypes were classified as MR, three genotypes as MS and nine as S. The highlights were the cultivars CD 116, CD 104, IPR 85 and line VI 07094 with yields exceeding 3000 kg / ha and severity lower than 6%. The three variables yield, incidence and severity showed significant correlation with each other.
O trigo (Triticum spp.) é uma gramínea cultivada e utilizada como fonte de energia no mundo todo, sendo cultivado em várias regiões do Brasil. No entanto, a severidade de algumas doenças e o controle químico ineficaz, vêm ameaçando a triticultura brasileira. Entre as doenças, a brusone do trigo causada pelo fungo Pyricularia grisea, vem ganhando um papel de destaque, podendo reduzir a produtividade das lavouras em até 70%. O controle químico da doença tem sido insatisfatório e existem poucas informações sobre resistência genética disponível na literatura. O uso da resistência é a melhor maneira de controle de doenças, tanto pelas vantagens do ponto de vista econômico, quanto ambiental. Diante desses fatos, o objetivo deste trabalho foi avaliar a resistência de genótipos de trigo à brusone para posterior uso em programas de melhoramento genético. Foram obtidos 10 isolados de diferentes regiões produtoras do cereal no Brasil. Os isolados foram repicados para meio BDA (batata, dextrose e Agar) e após desenvolvimento e purificação das colônias foram transferidos para meio AV (aveia e Agar), sendo mantidos sob temperatura de aproximadamente 25ºC e regime de luz de 12 horas, durante 10 dias, para que ocorresse esporulação do fungo. A concentração do fungo empregada nas inoculações foi ajustada para 1,2 x 105 esporos/mL. No primeiro experimento, as plantas foram inoculadas quando apresentavam quatro folhas. As plantas foram mantidas em condições controladas a 25ºC e avaliadas sete dias após a inoculação. As plantas foram classificadas conforme o tipo de infecção e, posteriormente, foram calculados o Espectro de Resistência Relativo (ERR) (porcentagem de isolados que o genótipo expressou resistência) e o Índice de Doença (ID) (resistência de um genótipo usando toda a gama de tipos de infecção). Os valores de ID foram considerados diferentes (p≤0,05) caso seus intervalos de confianças (95%) não se sobrepusessem. Os genótipos IVI 04033, VI 07443, VI 07505, IVI 04028, VI 07157, VI 04026, VI 98053 e VI 07160 apresentaram suscetibilidade a mais de 80% dos isolados. Cinco cultivares e quatro linhagens apresentaram ERR maior que 50% e IDs menores que 0,6. Dentre as linhagens, destacaram-se VI 04098 e VI 07094 com ERR maiores que 80%, se equiparando a variedade IPR 85. No segundo experimento, conduzido em condições de campo, a inoculação foi feita de forma escalonada, de acordo com o ciclo dos genótipos de trigo, quando as plantas atingiram o estádio 58-60 da escala de Zadoks (1974), sendo aplicado 1L de suspensão de conídios de P. grisea na concentração de 1,2 x 105/mL por parcela. A produtividade foi avaliada pela colheita de cada parcela útil (3 m2). A incidência da doença foi avaliada pela porcentagem de espigas infectadas e a severidade foi avaliada pela porcentagem de espiguetas infectadas em cada espiga. A produtividade variou de 879 a 3983 kg/ha; a incidência da doença variou de 0,86 a 84,24% e a severidade variou de 0,48 a 65,29%. Sete genótipos que foram classificados como MR, três genótipos como MS e nove como S. Destacaram-se as cultivares CD 116, CD 104, IPR 85 e a linhagem VI 07094 com produtividades superiores a 3000 kg/ha e severidades menores que 6%. As três variáveis: incidência, produtividade e severidade, apresentaram correlação significativa entre si.

Le beta-1,3-d-glucane est un constituant essentiel de la paroi cellulaire des champignons, synthetise chez les vegetaux principalement dans la fonction cicatricielle (callose). L'enzyme qui le synthetise, joue un role important dans la croissance mycelienne et peut etre une cible interessante pour des fongicides. La beta-1,3-d-glucane synthase (ec 2. 4. 1. 34) de pyricularia oryzae, champignon responsable de la fletrissure du riz, a ete caracterisee. Nous avons dans un premier temps mis au point un protocole d'extraction des membranes par des centrifugations fractionnees. L'enzyme a ensuite ete solubilisee a l'aide du detergent polyoxyethylene ether w1. Le produit synthetise a ete identifie par digestion a l'aide d'hydrolases specifiques, puis par chromatographie. En conditions optimales, l'activite specifique de l'extrait enzymatique partiellement purifie peut atteindre 10 nmoles de glucose incorporees / mg de proteines / minute. Les etudes biochimiques ont montre les caracteristiques de regulation du systeme enzymatique: l'activation par les ions calcium et magnesium, l'activation par les nucleotides triphosphates a faible concentration (gtp 10#-#8m, atp 10#-#6m) et l'absence de forme zymogene. L'importance de la partie lipophile des molecules inhibitrices a ete montree en etudiant l'inhibition par les detergents de la famille de l'octylglucoside. La fraction enzymatique solubilisee, puis purifiee par centrifugation en gradient de densite, a ete analysee par electrophorese en condition denaturante. Les peptides de 32, 46 et 54 kda sont correles a l'activite et pourraient correspondre a des sous-unites du complexe enzymatique. Une banque d'adn genomique en phage de p. Oryzae a ete construite. Un fragment du gene etg1 de s. Cerevisiae, codant pour une proteine membranaire impliquee dans la synthese de beta-1,3-glucane, a ete amplifie par pcr et utilise comme sonde. Des experiences d'hybridation ont revele la presence de sequences homologues chez p. Oryzae. Le criblage de la banque genomique a permis d'isoler un clone, en cours de sous-clonage pour le sequencage

Mestrado em Engenharia Agronómica - Proteção de Plantas - Instituto Superior de Agronomia
The present work had as objective to determine the duration of the cycle vegetative and to evaluate the susceptibility to rice blast disease of 19 rice advanced lines resulting from the improvement works performed by INIAV,I.P. in collaboration with the COTArroz, in “Salvaterra de Magos” and 12 commercial varieties. The susceptibility was determined under field conditions and greenhouse inoculation studies, having been used five isolated of Magnaporthe grisea of the Portuguese population of the pathogen and one isolated of reference of the Japanese population (JP 56 ). The beginning of tillering of the advanced lines and the varieties occurred between 19 and 29 days after sowing, the booting between 74 and 84 days and heading between 80 and 92 days. The duration of the vegetative cycle varied between 121 days and 140 days, having the majority of the studied advanced lines presented cycle greater than 130 days. In field test 60% of the advanced lines and 58% of commercial varieties were susceptible to leaf or panicle blast, having the advanced lines OP 1227 and OP 1229 and the commercial varieties “Ariete” and “Dardo” been most susceptible to leaf blast. In the study of inoculation 15.8% of the advanced lines presented susceptibility to all isolates, while no commercial variety presented susceptibility to all isolates.

Gray leaf spot, induced by Pyricularia grisea, is a disease of increasing importance in tall fescue in the southeastern United States. Previous research has shown that several herbicides may predispose turfgrasses to some diseases and that certain essential nutrients may have antagonistic effects on fungal plant pathogens. The objectives of this research were to evaluate the effects of herbicide and nutrient treatments on gray leaf spot development in tall fescue. Inoculation techniques were also evaluated for establishing gray leaf spot on tall fescue in controlled environments. Field studies revealed that 2,4-D applications resulted in significantly higher quality turf and lower gray leaf spot incidence than the untreated control. Turf treated with 2,4-D amine + mecoprop + dicamba also exhibited significantly less foliar blight symptoms than the untreated control. In vitro experiments revealed the growth-inhibiting effects of 2,4-D on P. grisea implicated in the field, as mycelial growth was completely inhibited at concentrations of 500 and 1000 mg L^-1. Colony growth was not affected at 2,4-D concentrations up to 100 mg L^-1. Phosphorous acid treatments resulted in a reduction in turf quality compared to an untreated control, as did manganese and zinc treatments. Foliar blight caused by P. grisea was substantially increased in H₃PO₃-treated plots in 2003, where a 40% difference in blighted turf was observed between plots that received H₃PO₃ treatments every 14 days and the untreated control. Area under the disease progress curve (AUDPC) analysis also revealed the significant detrimental effects of the phosphorous acid treatments. No significant differences in disease incidence or leaf spot size among nutrient treatments were observed in greenhouse treatments. Isolate selection was a significant factor for disease development and leaf spot size following spray inoculation under optimal environmental conditions. In general, disease incidence increased as inoculum density increased. Placing plants in covered containers or plastic bags immediately following inoculation for a 24-h period also appeared to promote disease development. Seeding rate did not have a significant effect on gray leaf spot development. We conclude that herbicide applications do not predispose tall fescue to gray leaf spot development and that applications of nutrients alone do not suppress development of gray leaf spot in tall fescue. Adjusting cultural practices as additional control measures for gray leaf spot does not appear to be a successful approach to managing this increasingly important disease.

A cultura de trigo (Triticum aestivum L.) é a segunda maior do mundo e o Brasil ocupa o segundo lugar de produção na América do sul. Entretanto, a produtividade desta cultura pode ser limitada devido à ocorrência de doenças como a brusone, causada pelo fungo Pyricularia grisea e a doença denominada giberela, causada pelo fungo Fusarium graminearum Populações bacterianas associadas à rizosfera de trigo podem apresentar potencial como agentes de controle biológico de diferentes fitopatógenos. Neste contexto, esta pesquisa foi direcionada ao estudo da composição da comunidade bacteriana rizosférica do trigo e a busca por micro-organismos com potencial para o controle biológico da brusone e da giberela. Assim, para melhor compreensão das comunidades associadas ao trigo, foram realizadas coletas em duas regiões diferentes no Brasil, sendo possível a obtenção de 606 estirpes entre bactérias e actinobactérias da rizosfera do trigo e de solo de cultivo da mesma cultura. Destas, 16 apresentaram, em testes in vitro, potencial antagonista diante dos fungos fitopatogênicos Pyricularia grisea e Fusarium graminearum com diferentes porcentagens de inibição. Dez dos isolados selecionados apresentaram similaridade com a família Streptomycetaceae, porém, quatro linhagens necessitam de estudos mais detalhados, pois a similaridade foi baixa, podendo indicar uma espécie ainda não descrita; quatro linhagens demonstraram similaridade com a família Bacillaceae e dois com a família Paenibacillaceae. Na avaliação de produção de metabólitos secundários com efeito inibitório, apenas dez apresentam potencial, porém estudos mais detalhados se fazem necessários para a confirmação deste mecanismo. A análise de diversidade bacteriana demonstrou uma maior abundância do filo Actinobacteria, seguido pelo filo Proteobacteria e Acidobacteria em ambas as áreas amostradas, entretanto, o filo Acidobacteria foi o que demonstrou a maior variação entre as classes presentes nas diferentes regiões estudadas, indicando uma seleção da comunidade de acordo com a variedade do cultivar e o estádio de desenvolvimento do vegetal. A comunidade bacteriana de trigo apresenta micro-organismos com potencial para a inibição dos fungos causadores da brusone e da giberela, porém o efeito destas linhagens deve ser melhor investigado em condições de campo. A compreensão das comunidades bacterianas associadas ao trigo pode se apresentar como uma importante ferramenta para direcionar a busca por antagonistas.
Wheat (Triticum aestivum) is the second largest crop in the world and Brazil is in the second position in the ranking of production in South America. However, its productivity can be limited due to the occurrence of diseases like wheat blast, caused by the fungus Pyricularia grisea and the disease called Fusarium head blight (FHB), caused by the fungus Fusarium graminearum. Bacterial populations associated to wheat rhizosphere may have potential to act as biological control agents of different plant pathogens. In this context, this research aimed to look at wheat rhizosphere bacterial community and the pursuit of microorganisms with potential for the biological control of wheat blast and FHB. Given this, in order to study wheat bacterial communities, data collection was carried out in two different regions in Brazil, returning 606 bacterial and actinomycetes isolates from wheat rhizosphere and bulk soil. Among these,, 16 strains revealed antagonistic potential against both plant pathogens Pyricularia grisea and Fusarium graminearum, with different percentages of inhibition. Ten strains were selected out of the 16 and showed similarity with the family Streptomycetaceae, whereas four of them displayed a low similarity, requiring a deeper analysis and might indicate new species. Four isolates showed similarity with the family Bacillaceae and two with the family Paenibacillaceae. On the assessment of production of secondary metabolites with inhibitory effects, only ten strains were positive, but more detailed studies are necessary to confirm this mechanism. The analysis of bacterial diversity revealed a larger abundance of the phylum Actinobacteria, followed by the phylum Proteobacteria and Acidobacteria in both areas, however, the phylum Acidobacteria revealed more variation among its classes when both araes were compared, indicating a selection of the community according to the cultivar and the developmental stage. Wheat bacterial community presents microorganism with inhibition potential against fungi responsible for wheat blast and FHB, yet the effect of such strains should be investigated closely under field conditions. The understanding of bacterial communities associated to wheat may be seen as an important tool to help in the search for antagonists.

Orientador: Paulo Cezar Ceresini
Resumo: Fungos do gênero Pyricularia apresentam uma ampla gama de plantas hospedeiras, com capacidade de infectar mais de 50 espécies de gramíneas nas quais causam a doença brusone. Há relatos que a espécies forrageira braquiária (Urochloa brizantha) é hospedeira de muitas espécies deste fungo. Muito embora a brusone em braquiária não cause prejuízos à produção de pastagens, a distribuição generalizada desta forrageira no país a torna uma importante fonte de inóculo do patógeno para diversas outras culturas de importância agrícola severamente danificadas pela brusone, em especial o trigo. A brusone do trigo é causada principalmente por Pyricularia graminis-tritici (Pygt), pode ser também ser atribuída a duas outras espécies de Pyricularia, P. pennisetigena (Pp) e P. urashimae (Pu). Dessa forma o objetivo deste estudo foi determinar a suscetibilidade bem como a reação de nove espécies e/ou cultivares do gênero Urochloa aos patógenos Pygt, Pp, Pu e P. grisea (Pg), a única espécie, até então, relatada como patógeno de braquiária no Brasil. De Pygt, foi avaliado também a virulência de sete raças do patógeno em espécies/cultivares de braquiária. Houve variação significativa na patogenicidade e na virulência e agressividade de espécies Pyricularia à diferentes espécies de Urochloa. As cultivares Ipypoã, BRS Tupi e Xaraés foram as mais resistentes às diferentes espécies Pygt, Pg, Pp e Pu do patógenos da brusone. Quando avaliamos a reação de Urochloa às raças B, C e D de P. graminis-tritici ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Fungi of the genus Pyricularia have a wide range of host plants, and are capable of infecting more than 50 species of grasses in which they cause blast disease. There are reports that the signal grass forage species (Urochloa brizantha) is host to many species of this fungus. Although the blast disease in signal grass does not cause damage to pasture production, the widespread distribution of this forage in the country makes it an important source of pathogen inoculum for several other crops of agricultural importance severely damaged by blast, especially wheat. The wheat blast is caused mainly by Pyricularia graminis-tritici (Pygt), but it can also be associated with to two other species of Pyricularia, P. pennisetigena (Pp) and P. urashimae (Pu). Therefore, the objective of this study was to determine the susceptibility and the reaction of nine species and / or cultivars of the genus Urochloa to the pathogens Pygt, Pp, Pu and P. grisea (Pg), the only species hitherto reported as a pathogen of Urochloa in Brazil. For Pygt, the virulence of seven pathogen races or virulence groups to Urochloa species / cultivars was also evaluated. There was significant variation in the pathogenicity and virulence and aggressiveness of Pyricularia species to different Urochloa species. When we evaluated the reaction of Urochloa to P. graminis-tritici races B, C and D, the Urochloa species / cultivars tested showed susceptibility. However, resistance was detected for the other Pygt races. The ... (Complete abstract click electronic access below)
Mestre

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).
Department of Biology

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Financiadora de Estudos e Projetos
Blast disease, caused by Magnaporthe grisea (anamorph Pyricularia grisea), is one of the main diseases of wheat and is disseminated throughout main producing states of the Country. It has been causing significant yield loss and is a limiting factor for the crop s expansion in central Brazil where the weather is highly favorable. The use of resistant cultivars can be influenced by weather conditions and concentration of inoculum. Chapter 1 of the present dissertation describes the influence of period of foliar wetness on the occurrence of blast in wheat seedlings in two experiments. The first one employed cultivars BH1146 (resistant) and BR40 (susceptible) inoculated with the Pyricularia isolate PR06- 03. In the second assay, the cultivars were BR18 (resistant) and Anahuac (susceptible) inoculated with the fungal isolate PR01-23. Five treatments were the period of wetness (6, 10, 14, 18 and 24h) in ten replications. Analysis was performed using a completely randomized design with a factorial plan of the treatments (five foliar wetness periods and 2 cultivars). Results showed that the minimum period needed for the development of the disease was 10 hours when inoculated with the isolate PR06-03. The longer the foliar wetness period the higher the incidence and severity of the disease regardless the resistance of cultivars. Chapter 2 aimed to determine the influence of the weather and concentration of P. grisea on the incidence and severity of blast. The experiment used totally randomized design with a factorial plan of the treatments: four concentrations (10³, 104, 105, 106 spores/ml) and two cultivars, ten repetitions. The wheat cultivars were BR18 (resistant) and Anahuac (susceptible) which were inoculated with 50ml of P. grisea suspension (isolate PR06-03) at the concentrations 10³, 104, 105, 106 spores/ml. The seedlings were submitted to temperatures of 22ºC and 28ºC for 18 hours of foliar wetness. The results showed that at 22ºC higher disease severity occurred on susceptible cultivar whereas the disease was the same for both cultivars at 28ºC. The resistant cultivar reacted like a susceptible when submitted to high temperature and high concentration of pathogen.
A brusone é uma das principais doenças do trigo e está disseminada nos principais estados produtores do país, causando danos significativos e sendo fator limitante para a expansão da cultura no Brasil central, principalmente por ser uma doença altamente influenciada pelo clima. Seu controle através de cultivares resistentes pode ser influenciado pelas condições climáticas e pela concentração de inóculo na lavoura. O Capítulo 1 desta dissertação descreve a influência do período de molhamento foliar na ocorrência da brusone, em plântulas de trigo, em dois experimentos. O primeiro com o isolado do fungo Pyricularia grisea (PR01-23) e duas cultivares de trigo no estádio de plântula, com reação diferenciada ao isolado (Anahuac suscetível e BR18 resistente) e o segundo com o isolado do fungo (PR06-03) e duas cultivares de trigo no estádio de plântula (BR40 suscetível e BH1146 resistente). Foram empregadas dez repetições de cinco tratamentos com os diferentes períodos de molhamento foliar (6, 10, 14, 18 e 24h). Avaliou-se a incidência e a severidade da brusone em porcentagem. A análise foi feita através de um delineamento estatístico inteiramente casualizado, com um esquema fatorial dos tratamentos (cinco períodos de molhamento e duas cultivares). Os resultados mostraram que o tempo mínimo requerido para o aparecimento da doença nas plântulas foi de 10 horas, quando inoculadas com o isolado PR01-23 e de 14 horas, quando inoculadas com o isolado PR06-03. Quanto maior o período de molhamento foliar, maior a incidência e a severidade da doença, independente da resistência da cultivar. O Capítulo 2 teve como objetivo determinar a influência da temperatura e concentração de inóculo de Pyricularia grisea na incidência e na severidade da brusone. O delineamento experimental utilizado foi inteiramente casualizado, com um esquema fatorial dos tratamentos: quatro concentrações de inóculo (10³, 104, 105 e 106 esporos/mL) e duas cultivares, dez repetições. Utilizou-se duas cultivares de trigo no estádio de plântula (BR18 resistente e Anahuac suscetível) que foram inoculadas com 50 mL de suspensão de P. grisea (isolado PR06-03) nas concentrações 10³, 104, 105 e 106 esporos/mL. As plantas foram submetidas às temperaturas de 22ºC e 28ºC por 18 horas de molhamento foliar. Avaliou-se a incidência e a severidade da brusone em porcentagem. Os resultados obtidos mostraram que à 22ºC a severidade foi maior na cultivar suscetível e igual para as cultivares a 28ºC. A cultivar resistente se comportou de forma semelhante a suscetível, quando submetida à alta temperatura e altas concentrações de inóculo.

Tobacco phylloplanins (T-phylloplanin) are a group of closely-related glycoproteins that are formed and disposed at the interface between the plant aerial surface (the phylloplane) and the atmosphere. They are synthesized in short procumbent trichomes and are secreted to aerial surfaces where they are thought to serve the plant as a first line of defense against fungal pathogens. Here it is shown using in vitro and in planta assays that tobacco and sunflower phylloplanins have broad-spectrum antifungal activities against spores - and also hyphae for two species - of several true fungi. Field tests show that T-phylloplanin reduces diseases caused by three important fungal pathogens of turf grasses. Tobacco phylloplanins are distinct proteins but they have properties in common with small, membrane-pore-forming, antimicrobial peptides formed by other organisms. To directly determine if T-phylloplanin has pore-forming activity we monitored conductivity change and specific ion leakage from spores and hyphae in suspension. Results indicate that phylloplanin causes fungal membrane disruption that leads to ion depletion and cell death. Having observed broad efficacy of T-phylloplanin against spores and/or hyphae of several true fungi, but no activity towards hyphae of the oomycetes, Pythium and Peronospora parasitica, we tested for possible effects on zoospores of the latter two pathogens. T-phylloplanin was shown to be effective against their zoospores, extending the efficacy of T-phylloplanin to include water molds. In the course of these experiments we also tested the effects of the diterpene cis-abienol that is secreted from tall trichomes of tobaccos and found this compound impacted zoospores and could prevent black shank disease caused by P. parasitica when applied to soil-grown tobaccos as a root drench. Thus, results of these studies with phylloplanins and cis-abienol, two different tobacco surface accumulated compounds are consistent with their serving the plant as first line of defense systems against a wide array of invading fungal pathogens. Phylloplanins and cis-abienol may be useful for controlling fungal diseases in tobacco float beds. The efficacy shown here for T-phylloplanin control of fungal pathogens of turf grasses in the field suggests that this natural product may find use in IPM of turf and other crops.

博士
國立臺灣大學
農藝學研究所
91
The rice breeding programs in Taiwan for developing high quality varieties with resistance to disease and insect usually use japonica rice as parents. To facilitate the breeding goals, the molecular linkage maps based on japonica × japonica crosses was developed. In this study, a molecular linkage map of japonica rice was constructed by 160 F2-derivided lines of TNG69 × Koshihikari population. It consisted of 135 DNA markers, totally spanning 1,350cM with an average interval of 14.67cM. According to the genotypic frequencies of molecular markers, segregation distortion was found in the F2 population. About 37.0% of investigated markers, or 50 out of 135, segregated distortedly from Medelian ratios. Distortion segregation was clustered on the linkage group A and H. Most makers of distortion segregation originated from male parent Koshihikari, with about 70.0%. The F2-derivded lines from TNG69×KHK were screened by greenhouse inoculation and field test. Both methods revealed resistance to rice blast was controlled by two major genes and several modifying genes in TNG69. Broad-sense heritability (H2B) was estimated on the combined analysis of variance. The value was 85.4% in greenhouse inoculation and 73.7% in field test. The eight sets data of disease test from 1999 to 2001 in two locations were analyzed using Mapmaker-QTL system. The result showed that all of DNA segments linkage with resistance to rice blast was detected in the interval of linkage group A, from R165 to R750-1 with the interval of 12.4cM. The resistance to rice blast of the CK block in nitrogen fertilizer treatment was detected in this interval, too. The phenotypic contribution value were from 21.3 to 74.2% and LOD score from 7.43 to 24.42 for all test data except the field test of the 1999. It was suggested that QTL in the interval R165-R750-1 of linkage A contained a major gene. The result of resistant test of brown plant hopper (BPH) showed that there were five major gene mechanism and one of them was recessive. The H2B value of BPH resistance was 73.9%. The BPH test at the year 2000 to 2002 was analyzed using Mapmaker-QTL system, and the result showed that all of the DNA segments linkage with BPH resistance were detected in the interval OPK16-R736 of linkage group G, with the length of 15.5cM. The phenotypic contribution value were from 36.8 to 79.9% and LOD score from 4.88 to 11.96 which suggested that QTL in interval OPK16-R736 of linkage G is a major gene. Twenty-three makers on linkage A (chromosome 12) were detected significantly related to rice blast resistance, and five makers on linkage G were detected significantly related to BPH at 0.01% resistance. The twenty-eight makers linkage with resistance were useful tools to be applied in marker-assisted-selection (MAS) for rice varieties resistant to rice blast or BPH with the stable yield. In the present, it was determined that expression consistent QTLs related with rice blast and BPH of F2-derivded lines in different environment. It is helpful that a substantial proportion of QTL affecting trait are consistent and stable across different environments. The QTLs related with rice blast were detected in greenhouse test, and all of them were expressed at least twice in the four time tested. This shows that disease test in greenhouse is more stable and representative than field test is. The effect of QTL mapping on the basis of different recording methods showed that recording serious scores of disease or insect resistance was better than recording the mean score. Two false QTLs were detected by recording mean score of rice blast resistance during three-year test in field. Therefore, it is suggested that recording serious scores gives meaningful results than recording mean score does.

Finger millet is the second most important cereal in Uganda after maize. The yields however, have remained low due to several constraints, such as finger millet blast disease and limited technology options. Therefore breeding investigations were conducted to determine farmer preferred traits, genetic variation, combining ability and genetic effects for head blast disease and head shapes, and other quantitative traits in finger millet. Among other traits, farmers preferred high grain yield potential, brown seed colour, compact head shape, tolerance to blast disease, high tillering ability, medium plant height, early maturity, tolerance to shattering and ease of threshing in new finger millet varieties. Path coefficient analysis indicated that the most important traits were grain mass head-1, tillering ability and reaction to head blast disease. Overall, the high heritabilities and genetic advance (GA) as a percentage of mean revealed the existence of variability which can be utilised through selection and/or hybridisation. The genotype x environment interaction (GEI) and stability analysis showed significant differences due to genotypes (58%), environments (10%) and GEI (32%). Twelve genotypes that combined high yield potential and stability were identified for advancement in the program. Both general (GCA) and specific combining ability (SCA) were significant for most traits, but GCA effects were more important for all the traits except for number of fingers head-1, finger width and panicle width. The Hayman genetic analysis confirmed importance of additive gene action for most of the traits and that additive-dominance model was adequate for explaining genetic variation in finger millet. The results also indicated that yield was controlled by recessive genes whereas blast resistance was controlled by dominant genes. At least two genes, probably three gene pairs and their interactions seemed to control head shape in finger millet. The interactions observed suggest recessive and dominant epistasis, and probably an inhibitor were involved. Seemingly, the gene for curving of fingers, when present in a dominant form prohibits opening of the heads; whereas the recessive form leads to open head shape irrespective of the gene conditions in the other loci. This study forms the baseline for future investigations and the basis for devising breeding strategy on finger millet head shapes.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Finger millet (Eleusine coracana) productivity in East Africa has remained low in all production agro-ecologies for decades owing to the low yielding potential of existing that are susceptible to the blast disease caused by the fungus Magnaporthe grisea (Hebert) Barr. and the limited research on the crop. The region holds large finger millet germpasm collections whose value is not yet been fully exploited. However, with the ongoing breeding efforts through hybridization, there is a need to comprehensively characterize the germplasm to identify valuable traits to address biotic and abiotic stresses that affect finger millet productivity. Studies on gene action and inheritance of key traits that contribute to yield improvement are also required to help formulate an effective breeding strategy for finger millet improvement. The objectives of this study were to (i) determine the genetic diversity in a set of germplasm from East Africa (ii) determine association between grain yield and its component traits (iii) identify genotypes for target production agro-ecologies (iv) identify blast resistant finger millet genotypes for use in breeding and production and (v) generate information on the inheritance of blast, grain yield and yield components for the development of an effective breeding strategy. A total of 340 finger millet accessions were collected from three countries in East Africa: Kenya, Tanzania and Uganda and 80 global minicore accessions sourced from ICRISAT-India. High phenotypic variability in the germplasm was recorded for 23 quantitative traits, blast reaction and five qualitative traits. Both morphological and molecular characterization (using SSR markers) of the 340 accessions revealed higher diversity within than among the countries Kenya, Tanzania and Uganda. Seven morphological clusters and three major genetic clusters were detected. Morphological diversity delineation was largely influenced by leaf sheath length, plant height, peduncle length, panicle exertion and grain yield. The mean polymorphic information content (PIC) of 19 polymorphic markers was 0.606 with mean alleles of 195 with sizes that ranged from 148-474 base pairs. The Kenyan and Tanzanian accessions had higher diversity than the Ugandan with the Kenyan and Ugandan, and the Kenyan and Tanzanian accessions being closely related than the Tanzanian and Ugandan. The low diversity in the Ugandan accessions could be attributed to higher research intervention in the country leading to the promotion and use of improved cultivars. Efforts have to be directed towards collection and conservation of valuable diversity before it is lost. The diversity in plant height, maturity, yield and blast reaction and the cluster groups detected in the germplasm should provide a basis for finger millet improvement through hybridization and selection. Higher genotypic than phenotypic correlations were recorded for most of the traits studied with grain yield having high positive correlations with finger width, grains per spikelet, threshing percent, peduncle length and panicle exertion. Both grain yield and days to flowering had negative correlations with all three blast types (leaf, neck and finger). Path coefficient analysis revealed that productive tillers per plant, 1000 grain mass, grains per spikelet and threshing percent had positive direct genetic effects on grain yield with strong indirect effects from several of the other traits which necessitates simultaneous selection for those traits with strong direct effects and those with strong indirect effects for grain yield improvement. High broad sense heritability estimates and high genetic advance as percent of mean were recorded in fingers per panicle, flag leaf sheath length, 1000 grain mass, finger length, peduncle length, panicle exertion, number of leaves per plant and leaf sheath length probably indicating the predominance of additive gene effects in controlling these traits hence the potential for improvement through selection. Adaptation and stability analysis using the GGE biplot model identified Lanet 2012 long rains, Serere 2012 long rains and Miwaleni 2012 long rains as the most discriminating environments for the low temperature, sub-humid mid altitude and dry lowland areas, respectively. Alupe 2012 long rains was the ideal environment for genotype discrimination for blast while Lanet 2012 long rains was best for grain yield. Genotypes G3, G5, G17, G25, G28, G36 and G71 were identified as being stable across environments and G1, G18, G19, G37, G54, G61, G74, G75, and G77 were found ideal for specific adaptation. Disease severity scores were highly negatively (P<0.01) correlated with days to flowering and grain yield suggesting that early lines suffered more disease damage leading to reduced yield. Resistant genotypes were slow blasting (probably associated with horizontal resistance) which may enable them to withstand blast pathogen variability for longer periods. Nine genotypes were identified with high resistance to blast and will be useful for breeding as blast resistance sources. Resistant genotypes had low AUDPC values and disease severity rating for the three blast types and vice-versa for susceptible genotypes. Further investigations need to be carried out to determine the possibility of the three blast types being controlled by the same genes. Early maturing blast susceptible genotypes with good yield potential could be utilized in areas with low blast prevalence. To understand the gene action for inheritance of the various traits 16 F2 families plus their four female and four male parents were evaluated at Alupe and Kakamega western Kenya under artificial blast inoculation. Significant additive genetic effects were recorded for all traits (except for finger width and grains per spikelet) meaning that improvement for these traits would be possible through the common selection methods for self pollinating crops. Parent lines KNE 392, and KNE 744 and IE 11 were found to be suitable for blast resistance breeding while Okhale 1 was found to be suitable for high grain yield and blast resistance improvement due to their high desirable GCA effects. Most of the F2 families showed transgressive segregation for the three blast types in either direction which gives hope for the development new pure lines with better blast resistance than the parents. Crosses IE 3104 x KNE 796, KAT FM 1 x Okhale 1, IE 11 x Okhale, IE 11 x P 224 and KNE 744 x KNE 392 have potential to generate lines with blast resistance due to their high desirable SCA effects. The F2 segregation distributions for blast indicated quantitative inheritance. However the one to four minimum number of genes (effective factors) detected for resistance control in all the three blast types was not in sync with the segregation patterns in the F2 families and further investigations are required. There were differences in segregation patterns between crosses which may suggest the presence of different resistance genes in the different parents used. This would call for gene pyramiding for durable resistance. These results confirm the potential of sourcing valuable parental stocks in the local germplasm for the development of genotypes to improve finger millet productivity in East Africa. Already some of the high yielding and blast resistant genotypes identified here have been incorporated in the regional cultivar trials. The diversity information generated will facilitate effective conservation and utilization of this germplasm. Results of gene action for inheritance of the various traits from this study will enable breeders to develop sound breeding strategies for finger millet improvement in the region.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.