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Melander, Margareta. "Transgenic resistance to pathogens and pests /." Alnarp : Dept. of Crop Science, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/a496.pdf.
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Geddes, Jennifer M. H., and University of Lethbridge Faculty of Arts and Science. "Fusarium head blight of barley : resistance evaluation and identification of resistance mechanisms." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2006, 2006. http://hdl.handle.net/10133/399.
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An evaluation of nineteen barley lines using three artificial inoculation methods concluded that spray inoculation was the most reproducible method and provided the greatest discrimination of resistance. Six of the nineteen barley lines were used for proteomic studies to identify defense responses following F. graminearum infection. All lines responded by inducing an oxidative burst and pathogenesis-related proteins. Differences in response magnitude and the proteins activated could be attributed to varying levels of FHB resistance amongst the barley lines. RNA microarray profiling and iTRAQ technology were used to study the interaction between two barley lines under five different treatments testing the effect of the fungus, trichothecene, and their interaction. Resistance was differentiated by the early induction of defense-related genes and the activation of the JA and ethylene defense pathways in Chevron, compared to the induction of a less efficient defense pathway in Stander; observed intra- and inter-cultivar differential responses are discussed.xvii, 196 leaves : ill. ; 29 cm.
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Soriano, Imelda Rizalina. "Novel inducible phytochemical defences against plant parasitic nematodes /." Title page, table of contents and summary only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phs7141.pdf.
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馮景良 and King-leung Fung. "Purification of Brassica juncea chitinase BJCHI1 from transgenic tobacco." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224374.
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Galagedara, Nelomie Nayanathara. "Identification of Quantitative Trait Loci for Resistance to Tan Spot in Durum Wheat." Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/28765.
Full textAbstract:
Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is a major foliar disease on wheat. The pathosystem involves three pairs of necrotrophic effector (NE) and host sensitivity (S) gene interactions, namely Ptr ToxA-Tsn1, Ptr ToxB-Tsc2 and Ptr ToxC-Tsc1. Additionally, genetic factors conferring race-nonspecific resistance have been identified. The objectives of this study were to map tan spot resistance QTL and investigate the role of NE-S interactions in disease in durum using association and bi-parental mapping. Evaluation of a worldwide collection of durum accessions allowed identifying highly resistant nineteen lines to multiple Ptr races. Association mapping revealed genomic regions on chromosomes 1A, 2B and 3B significantly associated with resistance to tan spot, which likely correspond to Tsc1, Tsc2 and racenonspecific resistance. Using a bi-parental population derived from Ben and PI 41025, we found that ToxA-Tsn1 interaction plays no significant role in disease, instead a major race-nonspecific QTL on chromosome 5A was identified.
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Freeborough, Michael-John 1971. "A pathogen-derived resistance strategy for the broad-spectrum control of grapevine leafroll-associated virus infection." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53285.
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Thesis (PhD)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: Grapevine leafroll-associated virus-3 is one of ten members of the C/osteroviridae that are known to infect grapevine. Nine of these viruses are associated with grapevine leafroll disease, of which GLRaV-1 and GLRaV-3 are the most important and widespread. Members of the C/osteroviridae are unique amongst the viruses, as it is the only known family whose members encode a heat shock protein 70 kOa homolog (Hsp70h). The Hsp70h is a movement protein (MP) that is required for the active translocation of the virion structure through the plasmodesmata into adjacent cells. Broad-spectrum resistance to unrelated viruses can be obtained by a pathogen-derived resistance (POR) strategy that is based on the expression of a dysfunctional MP in plants. The Hsp70h has two distinct domains. The N-terminal two thirds of the protein is an ATPase domain and shares high homology with the ATPase domains of all Hsp70h proteins from the C/osteroviridae and Hsp70 proteins from the prokaryote and eukaryote kingdoms. Conserved amino acids are found in the ATPase domain and are required for the positioning of the ATP at the catalytic site for ATP hydrolysis. The C-terminal domain is variable and the function of this domain in the Closteroviridae is not known. In prokaryote and eukaryote Hsp70 proteins, the C-terminal domain is required for protein-protein interactions. The American NY-1 isolate of GLRaV-3 has been sequenced and POR strategies have been attempted with the coat protein, divergent coat protein and replicase genes, but not with a dysfunctional form of the hsp70h gene. In this study, double-stranded RNA was isolated from a commercial vineyard with unknown virus status, but with distinct grapevine leafroll symptoms, and from two grapevine sources of known virus status, one with mild and one with severe symptoms. The GLRaV-3 hsp70h gene was amplified by RT-PCR from the dsRNA and the gene sequence was analysed. The hsp70h gene from the three virus sources contained more than 94% nucleotide sequence homology to the NY-1 isolate and the conserved amino acids required for ATPase activity were present. The hsp70h gene isolated from GLRaV-3 from a commercial Stellenbosch vineyard showing clear leafroll symptoms was selected for further work and was subjected to site-directed mutagenesis to engineer four point mutations in the gene. These four mutations resulted in the substitution of Asn for Asp", Gly for Thr1O, Lys for Glu 174 and Asn for Asp 197. The wild type (WT) and mutated (Mut) forms of the hsp 70h genes were cloned into a bacterial expression vector. Expression of both the WT- and Mut-Hsp proteins was achieved, and the protein was expressed in the insoluble inclusion bodies. All attempts to refold and isolate active proteins from the inclusion bodies were unsuccessful. Attempts to increase the concentration of soluble protein within the expressing bacteria were unsuccessful. Due to the lack of active protein, biochemical tests on the ATPase activity of the WT- and Mut-Hsp proteins could not be conducted. The wt- and mut-hsp genes were cloned into a plant expression vector for transformation into tobacco plants. These transformations were successful and gave rise to 22 Km' and 18 Km' plants from the WT- and Mut-Hsp constructs respectively. Two plant lines, M5 and M10, transformed with the mut-hsp transgene construct, appeared to have a high level of resistance to the challenging potato X potexvirus, whereas all the other tested plants were susceptible to the challenging virus. It was thus shown that a dysfunctional form of the GLRaV-3 Hsp70h could provide resistance to an unrelated virus in tobacco.
AFRIKAANSE OPSOMMING: Wingerdrolblaar-geassosieerde virus 3 (GLRaV-3) is een van 10 lede van die Closteroviridae wat wingerd kan infekteer. Nege van die virusse is met wingerdrolblaar geassosieer. Die GLRaV-1 en GLRaV-3 is die belangrikste en mees wyd verspreide lede van die rolblaar-geassosieerde Closteroviridae. Lede van die Closteroviridae is uniek in die opsig dat die virusse vir 'n 70 kDa-homoloë hitteresponsproteïen (Hsp70h) kodeer. Die Hsp70 is 'n bewegingsproteïen (MP) wat belangrik is vir die translokasie van die virus deur die plasmodesmata na die naasliggende sel. Breë-spektrum weerstand teen onverwante virusse kan behaal word deur 'n patogeen-afgeleide weerstandstrategie (POR), wat op die uitdrukking van 'n disfunksionele MP wat in plante uitgedruk word, gebaseer is. Die Hsp70hproteïen het twee gebiede. Die N-terminale gebied is In ATPase-gebied en toon hoë homologie met ander ATPase-gebiede van Hsp70h-proteïene van die Closteroviridae, asook die prokariotiese en eukariotiese koninkryke. Gekonserveerde aminosure wat belangrik is vir die posisionering van ATP in die katalitiese domein vir ATP-hidrolise is in die ATPase-gebied gevind. Die C-terminale gebied is variërend en die funksie van die gebied in die Closteroviridae is onbekend. In prokariotiese en eukariotiese Hsp70h-proteïene is die C-terminale gebied belangrik vir proteïenproteïen interaksies. Die nukleotiedvolgorde van die Amerikaanse NY-1-isolaat van GLRaV-3 is al bepaal en POR-strategieë is ook op die kapsiedproteïen, uiteenlopende kapsiedproteïen en die replikasie-proteïen uitgevoer, maar nog nie op 'n disfunksionele vorm van die Hsp70h-geen nie. In hierdie studie is dubbelstring-RNA (dsRNA) van 'n kommersiële wingerd met onbekende virusstatus wat rolblaarsimptome toon, geïsoleer, asook van twee wingerde met 'n bekende virusstatus, een met ligte en een met strawwe simptome. Die GLRaV-3 hsp70h-geen is met hulp van die polimerasekettingreaksie-metode (PKR) vanaf die dsRNA geamplifiseer en die geen se nukleotiedvolgorde is bepaal. Die hsp 70-gene van drie verskillende wingerde het meer as 94% homologie met die NY-1-isolaat getoon. Die gekonserveerde aminosure wat vir ATPase-aktiwiteit belangrik is, was teenwoordig. Die hsp70h-geen van GLRaV-3, wat uit 'n kommersiële wingerd met duidelike rolblaarsimptome in die Stellenbosch-gebied geïsoleer is, is vir verdere navorsing gekies en dit is aan setel-gerigte mutagenese blootgestelom vier mutasies van die geen te bewerkstellig. Die gevolg van hierdie vier mutasies was die verandering van Asn na Asp", Gly na Thr1o, Lys na Glu174 en Asn na Asp197. Die wilde (WT) en veranderde (Mut) vorms van die hsp-gene is in 'n bakteriese uitdrukkingsvektor gekloneer. Uitdrukking van beide die WT- en die Mut-Hspproteïene is behaal, maar die proteïene was in die onoplosbare fraksie geleë. Pogings om die onoplosbare proteïene te isoleer en in 'n aktiewe oplosbare vorm te verkry, was onsuksesvol. Verdere pogings om die proteïene in die oplosbare fraksie van die bakteriese ekspressiesisteem uit te druk, was ook onsuksesvol. As gevolg van die gebrek aan aktiewe proteïen kon biochemiese toetse nie op die ATPaseaktiwiteit van die WT- en Mut-Hsp proteïne gedoen word nie. Die wt- en mut-hsp-gene is ook in In plantekspressievektor gekloneer vir transformasie in tabakplante. Hierdie transformasies was suksesvol en het aanleiding gegee tot 22 kanamisienbestande (Km') en 18 Km' plante vanaf die WT- en Mut-Hspkonstrukte onderskeidelik. Twee plantlyne, M5 en M10, wat met die mut-hsptransgene getransformeer is, het 'n hoë vlak van weerstand teen die infekterende aartappelvirus X getoon in vergelyking met ander plante wat met die virus geïnfekteer is. Daar is dus bewys gelewer dat 'n disfunksionele vorm van die GLRaV-3 Hsp70h weerstand kan bied teen 'n onverwante virus in tabak.
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Rodríguez, Baixauli Ana María. "Genetic engineering of plant volatiles in fleshy fruits: pest repellency and disease resistance through D-limonene downregulation in transgenic orange plants." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/31655.
Full textAbstract:
Los terpenos constituyen el mayor grupo de metabolitos secundarios, siendo
componentes de las glándulas de aceites esenciales, de las flores y de las resinas defensivas
de plantas aromáticas, a los que proporcionan sus aromas y sabores característicos. Los
terpenos volátiles se asocian a la defensa de muchas especies de plantas, animales y
microorganismos contra depredadores, patógenos y competidores. Por otra parte, estos
compuestos parecen servir como señales para atraer a los polinizadores y agentes dispersores
de semillas, así como a depredadores de plagas. El estudio de compuestos orgánicos volátiles
emitidos durante el desarrollo del fruto y después del desafío con diferentes agentes bióticos
puede ayudar a conocer las interacciones de los frutos carnosos no sólo con vertebrados
dispersores y depredadores, sino también con insectos y microorganismos.
Los frutos carnosos son particularmente ricos en volátiles. En los frutos cítricos, los
monoterpenos son los principales componentes de las glándulas del aceite esencial de la
cáscara (flavedo), siendo el D-limoneno el más abundante (hasta 95% en la naranja). Esta
característica hace que los cítricos sean un buen sistema modelo para el estudio de la función
de los terpenos en los frutos. La biología molecular moderna permite la realización de
experimentos para comprobar la función de terpenos por medio del uso de organismos
transformados genéticamente en los que se han manipulado los niveles de acumulación de
dichos compuestos. En este trabajo, se ha utilizado un plásmido que alberga el cDNA completo
del gen de una limoneno sintasa de cítricos (CiTMTSE1) en orientación antisentido (AS) o
sentido (S) para modificar la expresión y la acumulación de D-limoneno en plantas de naranjo
dulce (Citrus sinensis L. Osb.). La acumulación de D-limoneno en las frutas AS se redujo
drásticamente pero la acumulación de otros terpenos también se modificó, afectando a
compuestos tales como alcoholes monoterpenos, cuya concentración se incrementó en la
cáscara de las frutas. Las plantas transformadas fueron morfológicamente indistinguibles de las
plantas control (WT) y de las plantas transformadas con el vector vacío (EV).
Los frutos transgénicos fueron desafiados con un insecto plaga y con diferentes
patógenos para probar si la alteración de los niveles de acumulación de estos volátiles daba
como resultado una mejora en la respuesta del flavedo frente a plagas y patógenos. Los
machos de la mosca mediterránea de la fruta (Ceratitis capitata) expuestos a las frutas AS y EV
en ensayos en túnel de viento fueron significativamente más atraídos por el aroma de los frutos
control EV. En otros experimentos de desafío con el hongo de la podredumbre verde
Penicillium digitatum y la bacteria causante de la cancrosis de los cítricos Xanthomonas
axonopodis subsp. citri, las frutas transgénicas con un contenido reducido de D-limoneno
mostraron elevada resistencia a estos patógenos. El alto contenido en D-limoneno en la
cáscara de naranjas maduras puede ser una señal para la atracción de plagas y
microorganismos que podrían estar involucrados en la facilitación del acceso a la pulpa de los
frugívoros dispersores de semillas.
El análisis de la expresión génica global en el flavedo de las frutas transgénicas vinculó
la disminución de D-limoneno y la reducción de la expresión de genes del metabolismo de
monoterpenos con la activación de la expresión de genes implicados en inmunidad innata,
incluyendo factores de transcripción, genes de quinasas implicadas en la entrada de Ca2+ en la
célula y genes implicados en la activación de las cascadas de MAPKs, con la consiguiente
activación de la ruta de señalización de ácido jasmónico (JA), lo que provocó la activación del
metabolismo de JA y un aumentó drástico de la acumulación de JA en la cáscara de la naranja
tras el desafío con P. digitatum, lo que explicaría la resistencia al menos a hongos necrotrofos
observada en las frutas.
Estos resultados indican que la acumulación de D-limoneno en la cáscara de la naranja
estaría implicada en la interacción trófica entre las frutas, insectos y microorganismos, lo cual
proporciona una visión mucho más amplia de las funciones de los terpenos en la naturaleza.
También representa una alternativa muy prometedora para incrementar la resistencia o
tolerancia de las plantas frente a patógenos y plagas.Terpenes, the largest group of secondary metabolites, are well known as constituents of essential oils, floral scents and defensive resins of aromatic plants, to which they impart their characteristic aromas and flavors. Terpene volatiles defend many species of plants, animals and microorganisms against predators, pathogens and competitors. Moreover, those compounds seem to serve as advertisements to attract pollinators and seed-dispersal agents as well as pest predators. The study of VOCs emitted during fruit development and after challenge with different biotic agents may help to determine the interactions of fleshy fruits not only with legitimate vertebrate dispersers and predators, but also with insects and microorganisms. Fleshy fruits are particularly rich in volatiles. In citrus fruits, monoterpenes are the main components of the essential oil glands of the peel, being D-limonene the most abundant one (up to 95% in orange fruits). This characteristic makes citrus a good model system for studying the function of terpenes in plants. Modern molecular biology now enable experiments to test terpenoid function by the use of genetically transformed organisms in which terpene levels have been manipulated. In this work, a plasmid harboring the complete cDNA of a citrus limonene synthase gene (CiTMTSE1) in antisense (AS) or sense (S) orientation was used to modify the expression and accumulation of D-limonene of sweet orange (Citrus sinensis L. Osb) plants. D-limonene accumulation in AS fruits was dramatically reduced but the accumulation of other terpenoids was also modified, such as monoterpene alcohols, whose concentration increased in the peel of fruits. Genetically transformed plants were morphologically indistinguishable from wild-type (WT) and empty vector (EV) control plants. Transgenic fruits were challenged against a pest and different pathogens to test whether volatile profile alteration results in an improvement in the response of the fruit flavedo against them. Males of the Mediterranean fruit fly (Ceratitis capitata) exposed to AS fruits versus EV in wind tunnel assays were significantly more attracted to the odor of EV control fruits. In separate experiments with the green mould rot of citrus fruits and citrus canker caused by Penicillium digitatum and Xanthomonas axonopodis subsp. citri, respectively, transgenic fruits with a reduced content in D-limonene showed resistance to both pathogens. High D-limonene content in mature orange peels may be a signal for attractiveness of pests and microorganisms which might be likely involved in facilitating the access to the pulp of seed dispersal frugivores. A global gene expression analysis of the flavedo of AS transgenic fruits linked the decrease of D-limonene and monoterpene metabolism to the up-regulation of genes involved in the innate immunity response, including transcription factors together with Ca2+ entry into the cell and activation of MAPK cascades, contributing to activation of jasmonic acid (JA) signaling, which triggered the up-regulation of JA metabolism and drastically increased the accumulation of JA in orange peels upon fungal challenge, explaining the resistance to necrotrophic fungi observed in AS fruits. These results indicate that limonene accumulation in the peel of citrus fruit appears to be involved in the successful trophic interaction between fruits, insects, and microorganisms and provide a much more comprehensive view of roles of terpenes in nature. It also represents a very promising alternative for increasing resistance or tolerance of plants to pathogens.
Rodríguez Baixauli, AM. (2013). Genetic engineering of plant volatiles in fleshy fruits: pest repellency and disease resistance through D-limonene downregulation in transgenic orange plants [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31655
TESIS
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Njom, Henry Akum. "Mechanism and synchronicity of wheat (Triticum aestivum) resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1." Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2700.
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Wheat (Triticum aestivum and T. Durum) is an extremely important agronomic crop produced worldwide. Wheat consumption has doubled in the last 30 years with approximately 600 million tons consumed per annum. According to the International Maize and Wheat Improvement Center, worldwide wheat demand will increase over 40 percent by 2020, while land as well as resources available for the production will decrease significantly if the current trend prevails. The wheat industry is challenged with abiotic and biotic stressors that lead to reduction in crop yields. Increase knowledge of wheat’s biochemical constitution and functional biology is of paramount importance to improve wheat so as to meet with this demand. Pesticides and fungicides are being used to control biotic stress imposed by insect pest and fungi pathogens but these chemicals pose a risk to the environment and human health. To this effect, there is re-evaluation of pesticides currently in use by the Environmental Protection Agency, via mandates of the 1996 Food Quality Protection Act and those with higher perceived risks are banned. Genetic resistance is now a more environmental friendly and effective method of controlling insect pest and rust diseases of wheat than the costly spraying with pesticides and fungicides. Although, resistant cultivars effectively prevent current prevailing pathotypes of leaf rust and biotypes of Russian wheat aphid from attacking wheat, new pathotypes and biotypes of the pathogen/pest may develop and infect resistant cultivars. Therefore, breeders are continually searching for new sources of resistance. Proteomic approaches can be utilised to ascertain target enzymes and proteins from resistant lines that could be utilised to augment the natural tolerance of agronomically favourable varieties of wheat. With this ultimate goal in mind, the aim of this study was to elucidate the mechanism and synchronicity of wheat resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1. To determine the resistance mechanism of the wheat cultivars to leaf rust infection and Russian wheat aphid infestation, a proteomics approach using two-dimensional gel electrophoresis was used in order to determine the effect of RWA SA1 on the wheat cultivars proteome. Differentially expressed proteins that were up or down regulated (appearing or disappearing) were identified using PDQuestTM Basic 2-DE Gel analysis software. Proteins bands of interest were in-gel trypsin digested as per the protocol described in Schevchenko et al. (2007) and analysed using a Dionex Ultimate 3000 RSLC system coupled to an AB Sciex 6600 TripleTOF mass spectrometer. Protein pilot v5 using Paragon search engine (AB Sciex) was used for comparison of the obtained MS/MS spectra with a custom database containing sequences of Puccinia triticina (Uniprot Swissprot), Triticum aestivum (Uniprot TrEMBL) and Russian wheat aphid (Uniprot TrEMBL) as well as a list of sequences from common contaminating proteins. Proteins with a threshold of ≥99.9 percent confidence were reported. A total of 72 proteins were putatively identified from the 37 protein spots excised originating from either leaf rust or Russian wheat aphid experiments. Sixty-three of these proteins were associated with wheat response to stress imposed by RWA SA1 feeding while 39 were associated with infection by Puccinia triticina. Several enzymes involved in the Calvin cycle, electron transport and ATP synthesis were observed to be differentially regulated suggesting greater metabolic requirements in the wheat plants following aphid infestation and leaf rust infection. Proteins directly associated with photosynthesis were also differentially regulated following RWA SA1 infestation and P.
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Maios, Claudia. "Expression of defence-related genes in sugar beet plants infected with Rhizoctonia solani and treated with benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH)." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99349.
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The chemicals inducers SA, BABA, and BTH were tested as seed treatment and soil drench on a partial-resistant cultivar of sugar beet grown in sand infested with the Rhizoctonia solani AG 2-2IIIB. In another series of experiments, BTH was applied as soil drench on sugar beet plants inoculated with R. solani. The chemical inducers were ineffective in reducing pre-emergence damping-off and post-emergence plant mortality. Despite these results, treatment with BTH altered the levels of expression ratios of four defence encoding genes associated with systemic resistance: chitinase, peroxidase, chalcone isomerase, and chalcone synthase. BTH sensitised sugar beet plants without the necessity of R. solani infection to up-regulate substantially the transcript level ratios of chalcS and chit3, while levels of chalcI were down-regulated levels below 1. Of interest, was the significant increase of transcript levels of chit3 in sugar beet plants infected with R. solani and treated with BTH. In conclusion, sugar beet plants were capable of over expressing selected genes in response to a chemical inducer, but contrary to what had been reported, gene activation in sugar beet as a result of BTH treatment does not confer disease resistance against R. solani.
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Williams, Kevin John. "Biological and genetic studies of wheat resistance to Heterodera avenae." Title page, summary and contents only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phw7238.pdf.
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Du, Min. "A greenhouse screening method for resistance to gray leaf spot in maize." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/42953.
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Filkowski, Jody, and University of Lethbridge Faculty of Arts and Science. "The effect of pathogens on plant genome stability." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, 2004, 2004. http://hdl.handle.net/10133/254.
Full textAbstract:
Resistance (R) genes, a key factor in determining the resistance of plants, have been shown often to be highly allelic entities existing in duplicated regions of the genome. This characteristic suggests that R-gene acquisition may have arisen through frequent genetic rearrangements as a result of transient, reduced genome stability. Tabacco plants transgenic for a recombination construct exhibited reduced genome stability upon infection with a virulent pathogen (tobacco mosaic virus). The reduced genome stability manifested as an increase in recombination events in the transgene. Such increases were observed following a virulent pathogen attack. This increase in recombination was shown to be systemic and was observed prior to systemic viral movement suggesting the presence of a systemic recombination signal. Further molecular analyses revealed that specific R-gene loci experience a large frequency of rearrangements following a virulent pathogen encounter. The possible targeting of instability to R-gene regions may be controlled through epigenetic processes, in particular, DNA methylation.xiii, 119 leaves ; 29 cm.
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Suidgeest, Faira. "Evaluation of two pathogen-derived resistance strategies for Grapevine leafroll-associated virus 3." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96776.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Grapevine leafroll disease (GLD), caused by the members of the family Closteroviridae, is one of the most economic important viral diseases affecting grapevine. Grapevine leafroll associated virus 3 (GLRaV-3), of the genus Ampelovirus, is the most widespread member of the leafroll associated virus family. To prevent the spread of GLD, management strategies such as rogueing and insect vector control are required to limit crop losses. Alternative control strategies based on genetic modification of the grapevine genome, such as pathogen-derived resistance (PDR), is proven to be effective in conferring resistance to several viruses. Therefore, the focus of this study was to evaluate pathogen-derived resistance strategies for GLRaV-3 using the following two approaches; 1) evaluation of transgenic plants expressing a dysfunctional GLRaV-3 heat shock protein 70 homolog (HSP70h) in order to confer resistance against GLRaV-3, and 2) the construction of artificial microRNAs (amiRNAs) to use as a tool for silencing specific sequences of GLRaV-3 in the grapevine host and the development of an amiRNA-mediated silencing validation system. In the first part of this study, six transgenic plant lines (plant lines #1, #3, #9, #14, #15 and #17) as well as a non-modified plant line, were inoculated with GLRaV-3 by grafting buds of each onto GLRaV-3 infected plant material. After approximately five months, GLRaV-3 virus titres of all grafted plants were quantified relative to two reference genes using RT-qPCR. Results were evaluated by comparing the relative virus titre of each transgenic plant line to that of the non-modified control plant line. Results showed that resistance levels of plant line #3 was significantly enhanced (>99%) and remarkably, plant line #14, showed to be more susceptible to the virus. The second part of the study was the construction and validation of amiRNAs targeting GLRaV-3 sequences. Two 21 nt regions of GLRaV-3 were successfully incorporated into miRNA backbone vvi167b of grapevine. Moreover, target constructs were developed by incorporating corresponding GLRaV-3 target sequences into the 3’ UTR of a green fluorescence protein (GFP) gene. Subsequently, the target constructs were co-infiltrated with the constructed amiRNA in Nicotiana benthamiana and GFP expression levels were quantified to determine the silencing efficiency of the amiRNAs. Results showed that the amiRNAs were successful in silencing the GFP target construct, however, they were not specific in silencing exclusively their corresponding target. These amiRNA constructs are ideal for further viral studies to determine the efficiency of silencing GLRaV-3 in GLD infected grapevines.
AFRIKAANSE OPSOMMING: Wingerd rolblaar siekte (GLD), wat veroorsaak word deur die lede van die familie Closteroviridae, is een van die ekonomies mees belangrike virus siektes van wingerd. Grapevine leafroll-associated virus 3 (GLRaV-3), van die genus Ampelovirus, is die mees wydverspreide lid van die rolblaar geassosieerde virus familie. Om die verspreiding van GLD te voorkom, is bestuur strategieë, soos die verwydering van geïnfekteerde plante en insekvektor beheer, ’n vereiste om oes verliese te beperk. Alternatiewe beheer strategieë gebaseer op genetiese modifikasie van die wingerdgenoom, soos patogeen-afgeleide weerstand (PDR), is bewys om effektief te wees in die verlening van weerstand teen verskeie virusse. Daarom was die fokus van hierdie studie om patogeen-afgeleide weerstand strategieë vir GLRaV-3 te evalueer met behulp van die volgende twee benaderings; 1) die evaluering van transgeniese plante wat 'n disfunksionele GLRaV-3 hitte-skok proteïen 70 homoloog (HSP70h) uitdruk, ten einde weerstand te verleen teen GLRaV-3, en 2) die konstruksie van kunsmatige mikroRNAs (amiRNAs) om te gebruik as 'n instrument vir die ondrukking van spesifieke genoomvolgordes van GLRaV-3 in die wingerd gasheer en die ontwikkeling van ’n stelsel om amiRNA-bemiddelde onderdrukking te bevestig. In die eerste deel van hierdie studie, is ses transgeniese plant lyne (plant lyne # 1, # 3, # 9, # 14, # 15 en # 17) sowel as 'n nie-gemodifiseerde gesonde plant lyn, geïnokuleer met GLRaV- 3 deur enting van ogies van elk op GLRaV-3 besmette plantmateriaal. Na ongeveer vyf maande, is GLRaV-3 virus konsentrasies van alle ingeënte plante gekwantifiseer relatief tot twee verwysing gene deur gebruik te maak van tru-transkripsie kwantitatiewe PCR (RTqPCR). Resultate is geëvalueer deur die relatiewe virus konsentrasie van elke transgeniese plant lyn te vergelyk met dié van die nie-gemodifiseerde kontrole lyn. Resultate het getoon dat weerstand vlakke van plant lyn # 3 beduidend verbeter is (> 99%) en merkwaardig is plant lyn # 14 bewys om meer vatbaar vir die virus te wees. Die tweede deel van die studie was die konstruksie en bevestiging van kunsmatige mikroRNAs (amiRNAs) wat GLRaV-3 genoomvolgordes teiken. Twee 21 nt streke van GLRaV-3 is suksesvol geïnkorporeer in die ruggraat van wingerd mikroRNA vvi167b. Verder is teiken konstrukte ontwikkel deur die inkorporering van ooreenstemmende GLRaV-3 teiken genoomvolgordes in die 3'UTR (3’ ongetransleerde area) van 'n groen fluoressensie proteïen (GFP) geen. Daarna is die teiken konstrukte gesamentlik geïnfiltreer met die gekonstrueerde amiRNA in Nicotiana benthamiana en GFP uitdrukkingsvlakke is gekwantifiseer deur die onderdrukkingsdoeltreffendheid van die amiRNAs te bepaal. Resultate het getoon dat die amiRNAs suksesvol was in die onderdrukking van die GFP teiken konstruk, maar hulle was egter nie-spesifiek in die eksklusiewe onderdrukking van die ooreenstemmende teiken. Hierdie amiRNA konstrukte is ideaal vir verdere virus studies om die doeltreffendheid van GLRaV-3 onderdrukking in GLD besmette wingerdstokke te bepaal.
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Presello, Daniel A. "Studies on breeding of maize for resistance to ear rots caused by Fusarium spp. and on the occurrence of viruses in maize in eastern Canada." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38260.
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Responses from pedigree selection for resistance to gibberella ear rot were assessed in four maize (Zea mays L.) populations, two selected after inoculation of Fusarium graminearum (Schwabe) macroconidia into the silk channel and two selected after inoculation into developing kernels. Responses were significant in both populations selected for silk resistance and in one of the populations selected for kernel resistance. Selection was more effective in later generations and genetic gains were associated with among-family selection but not with within-family selection. Results obtained here indicate that responses to selection could be more efficiently obtained by applying high selection intensities in advanced generations, by managing earlier generations as bulks and by reducing the number of plants per family. In another experiment, a wide sample of Argentine maize germplasm was evaluated for silk and kernel resistance to gibberella ear rot and to fusarium ear rot (caused by F. verticillioides (Saccardo) Nirenberg [=F. moniliforme (Sheldon)]. Several entries exhibited disease resistance in comparison with local check hybrids, particularly for fusarium ear rot, the most prevalent ear rot in Argentina. Results obtained in this study suggested the presence of general mechanisms controlling silk and kernel resistance to both diseases. In a supplementary study, viral diseases were surveyed in maize fields from the provinces of Ontario and Quebec in 1999 and 2000. Barley yellow dwarf was found in 1999. Sugarcane mosaic, maize dwarf mosaic and wheat streak mosaic were found in 2000. These diseases were not important for grain-maize planted in May, the most prevalent kind of maize crop in these provinces. Some of these diseases, such as sugarcane maize mosaic and maize dwarf mosaic were found important only in maize fields planted during or after the month of June, and this is of commercial relevance only for sweet corn.
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Rufener, George Keith. "A genetic and biochemical study of the antibiosis mechanism of host-plant resistance in soybeans to the Mexican bean beetle /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487335992902504.
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Podrebarac, Frances Ann. "The Relative Nitrogen Fixation Rate and Colonization of Arbuscular Mycorrhizal Fungi of Iron Deficient Soybeans." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29600.
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Soybeans (Glycine max L. Merr.) are a symbiont of two beneficial associations:
biological nitrogen fixation (BNF) with Bradyrhizobium japonicum, and arbuscular
mycorrhizal fungi (AMF). Within the Northern Great Plains of the USA, iron deficiency
chlorosis (IDC) of soybean is a yield-limiting factor. The effects of IDC on BNF and AMF
are not well defined. This study was conducted to determine the effects of IDC on BNF
and AMF. A laboratory study was performed to compare three methods of measuring
ureide-N, a product of BNF in soybeans. Field studies in soybean were performed at three
locations at eastern N011h Dakota. The experimental design was a factorial combination of
three cultivars and three treatments. The three cultivars, in order of decreasing chlorosis
susceptibility, were NuTech NT-0886, Roughrider Genetics RG 607, and Syngenta S01-C9
RR. The three treatments were control, Sorghum bicolor L. companion crop planted with
the soybean seed, and FeEDDHA applied with the soybean seed. Chlorosis severity was
the greatest and least for the NuTech and Syngenta cultivars, respectively. The FeEDDHA
treatment decreased chlorosis severity. Ureide levels were abnormally high in plants
severely stunted by JDC. The excess accumulation of ureides in IDC-stunted plants
suggests that plant growth was reduced more than the rate of nitrogen fixation. The AMF
population \vas at an adequate level at all locations and not affected by cultivar or
treatment, in general. In the laboratory study, the Patterson et al. method had greater ureide
concentrations due to the non-specific measuring of ammonium compounds compared to
the Vogels and Van der Drift and Goos methods.North Dakota Soybean Council
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Ramburan, Viresh Premraj. "Genetic mapping of adult plant stripe rust resistance in the wheat cultivar Kariega." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53438.
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Thesis (PhD (Agric)) -- Stellenbosch University, 2003.ENGLISH ABSTRACT: Stripe (yellow) rust of wheat, caused by Puccinia striiformis f.sp. tritici, was first detected as a single introduction into South Africa in 1996. Two additional pathotypes have since been identified. Control of the disease may be achieved by use of genetic adult plant resistance (APR) as is present in the local cultivar 'Kariega'. The aim of this project was to understand the genetic basis of the APR in 'Kariega' to facilitate breeding of new varieties with genetic resistance to stripe rust. A partial linkage map of a 'Kariega X Avocet S' doubled haploid population covering all 21 wheat chromosomes was generated using 208 DNA markers, viz, 62 SSR, 133 AFLP, 3 RGA and 10 SRAP markers, and 4 alternative loci. The different marker techniques detected varying polymorphism, viz, overall SSR: 46%, AFLP: 7%, SRAP: 6% and RGA: 9%, and the markers produced low levels of missing data (4%) and segregation distortion (5%). A significant feature of the linkage map was the low polymorphism found in the D genome, viz, 19% of all mapped DNA markers, 11% of all AFLP markers and 30% of the total genome map distance. A region exhibiting significant segregation distortion was mapped to chromosome 4A and a seedling resistance gene for stem rust (Puccinia graminis f.sp . tritici), Sr26, mapped to chromosome 6A close to three SSR markers. The leaf tip necrosis gene, Ltn, which was also segregating in the population, mapped to chromosome 7D. Protocols for SRAP and RGA were optimised, and SRAP marker use in wheat genetic linkage studies is reported for the first time. The linkage map was used together with growth chamber and replicated field disease scores for QTL mapping. Chromosomes showing statistically significant QTL effects were then targeted with supplementary SSR markers for higher resolution mapping. The quality of disease resistance phenotypic data was confirmed by correlation analysis between the different scorers for reaction type (0.799±0.023) and for transformed percentage leaf area infected (0.942±0.007). Major QTL were consistently identified on chromosome 7D (explaining some 25-48% of the variation) and on chromosome 2B (21-46%) using transformed percentage leaf area infected and transformed reaction type scores (early and final) with interval mapping and modified interval mapping techniques. Both chromosomal regions have previously been identified in other studies and the 7D QTL is thought likely to be the previously mapped APR gene Yr 18. Minor QTL were identified on chromosomes lA and 4A with the QTL on 4A being more prominent at the early field scoring for both score types. A QTL evidently originating from 'Avocet S' was detected under growth chamber conditions but was not detected in the field, suggesting genotype-environment interaction and highlighting the need for modifications of growth chamber conditions to better simulate conditions in the field. The genetic basis of the APR to stripe rust exhibited by 'Kariega' was established by mapping of QTL controlling this trait. The linkage map constructed will be a valuable resource for future genetic studies and provides a facility for mapping other polymorphic traits in the parents of this population with a considerable saving in costs.
AFRIKAANSE OPSOMMING: Streep of geelroes van koring word veroorsaak deur Puccinia striiformis f. sp tritici, en is die eerste keer in 1996 in Suid-Afrika na introduksie van 'n enkele patotipe waargeneem. Twee verdere patotipes is sedertdien in Suid-Afrika gei"dentifiseer. Beheer van die siekte word veral moontlik gemaak deur die gebruik van genetiese volwasseplantweerstand soos gei"dentifiseer in die plaaslike kultivar 'Kariega'. Die doel van hierdie studie was om die genetiese grondslag van die streeproesweerstand te ontrafel ten einde die teling van nuwe bestande kultivars moontlik te maak. 'n Verdubbelde haplo1ede populasie uit die kruising 'Kariega X Avocet S' is aangewend om 'n gedeeltelike koppelingskaart vir die volle stel van 21 koring chromosome saam te stel. Die kaart het uit 208 DNA merkers, nl., 62 SSR, 133 AFLP, 3 RGA, 10 SRAP merkers en 4 ander lokusse bestaan. Totale polimorfisme wat deur die verskillende merkersisteme opgespoor is, was as volg: SSR: 46%, RGA: 9%, AFLP: 7% en SRAP: 6%. Die mate van ontbrekende data was gering (4%) asook die mate van segregasie distorsie (5%) van 'n enkele geval wat op chromosoom 4A gekarteer is. 'n Prominente kenmerk van die koppelingskaart is die relatiewe gebrek aan polimorfiese merkers op die D-genoom, nl., slegs 19% van alle DNA merkers en 11% van alle AFLP merkers wat slegs 30% van die totale genoom kaartafstand bestaan het. Die stamroes (Puccinia graminis f. sp. tritici) saailingweerstandsgeen, Sr26, karteer op chromosoom 6A naby drie SSR merkers. Die geen vir blaartipnekrose, Ltn, karteer op chromosoom 7D. Protokolle vir SRAP en RGA merkers is ge-optimiseer en gebruik van SRAP merkers in koppelings-analise word vir die eerste keer in koring gerapporteer. Die koppelingskaart is in kombinasie met groeikamerdata en gerepliseerde veldproefdata gebruik om die gene (QTL) vir volwasseplant streeproesweerstand te karteer. Chromosome met statisties betekenisvolle QTL is met aanvullende SSR merkers geteiken om die resolusie van kartering verder te verhoog. Die kwaliteit van fenotipiese data, soos in die proewe aangeteken, is bevestig deur korrelasies te bereken tussen lesings geneem deur onafhanklike plantpataloe (0.799 ± 0.023 vir reaksietipe en 0.942 ± 0.007 vir getransformeerde persentasie blaaroppervlakte besmet). Hoofeffek QTL vir die twee maatstawwe van weerstand is deur middel van die metodes van interval QTL kartering en gemodifiseerde interval QTL kartering konsekwent op chromosome 7D (25-48% van variasie verklaar) en 2B (21-46% van variasie verklaar) ge"identifiseer. In vorige studies is aangetoon dat beide chromosome 7D en 2B QTL vir volwasseplant streeproesweerstand dra. Die 7D QTL is waarskynlik die weerstandsgeen, Yr 18. QTL met klein effekte op weerstand is op chromosome lA en 4A ge"identifiseer. Die effek van laasgenoemde geen was meer prominent in die velddata in die vroee datum van weerstandsbeoordeling. Een QTL, afkomstig van 'Avocet S', is slegs onder groeikamertoestande identifiseerbaar. Dit dui op moontlike genotipe-omgewing wisselwerking en beklemtoon die noodsaaklikheid om aanpassings te maak in groeikamertoestande vir beter simulasie van veldproeftoestande. Die genetiese grondslag van volwasseplantweerstand teen streeproes in die kultivar 'Kariega' is deur QTL kartering bepaal. Die 'Kariega X Avocet S' koppelingskaart kan as 'n waardevolle basis dien vir toekomstige genetiese ontledings van ander polimorfiese kenmerke in die populasie.
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McQualter, Richard Bruce. "Production and evaluation of transgenic sugarcane plants with pathogen-derived resistance to Fiji disease virus." Thesis, Queensland University of Technology, 2003.
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Van, Straten Celene Debra. "The construction of plant expression vectors for the introduction of leafroll disease resistance in grapevine." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51950.
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Thesis (MSc)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: Grapevine leafroll is one of the most damaging viral diseases that affect many viticultural regions of the world. Numerous reports over the last few years have associated closterovirus-like particles with leafroll disease. To date, eight serologically distinct closteroviruses have been isolated from leafroll infected vines, of which grapevine leafroll associated closterovirus-3 (GLRaV-3) is the best characterized. Virus resistance in transgenic plants based on the expression of a virusderived gene is known as pathogen-derived resistance. The viral coat protein (CP) gene, which expresses a structural protein responsible for coating the virus particles, was used in the first demonstration of virus-derived resistance. Coat protein-mediated resistance is currently the most feasible and most widely used method to obtain virus resistance in crop plants. The CP gene of a South African isolate of GLRaV-3 infected grapevine was isolated, cloned and sequenced. Double stranded RNA (dsRNA) was extracted from GLRaV-3 infected material and a high molecular weight band, of -18 kb was identified from infected vines. The dsRNA was used as a template in a reverse transcription PCR together with GLRaV-3 CP gene specific primers for the amplification of the GLRaV-3 CP gene (975 bp). The GLRaV-3 CP gene was cloned into the pGem®-T Easy vector. Clones hosting the CP gene in the sense (pLR3CP+) and antisense (pLR3CP-) orientations respectively were obtained. The sequence obtained from these two clones showed 99.26 % similarity to the only other GLRaV-3 CP nucleotide sequence available. The GLRaV-3 CP gene was excised from pLR3CP+ and pLR3CP- and subcloned into a plant expression vector, pCAMBIA 3301 in the sense (pCamBLR3CP+) and antisense (pCamBLR3CP-) orientations respectively, therefore enabling sense and antisense gene expression in transgenic plants. The GLRaV-3 CP gene was also subcloned from pCamBLR3CP+ into another plant expression vector, pCAMBIA 2301 in the sense orientation and designated as pCVSLR3CP+. These three constructs were given to Dr. M. Vivier (Institute for Wine Biotechnology, Stellenbosch) for grapevine transformation experiments. Two of these constructs, pCamBLR3CP+ and pCamBLR3CP- as well as pCAMBIA 3301 were used to transform Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. Plants were selected for their ability to withstand the herbicide, Basta. This resistance is due to the presence of a plant selectable marker gene on each of these constructs, known as the bar gene. PCR with GLRaV-3 CP gene specific primers showed no amplification of the GLRaV-3 CP gene in the plants transformed with pCamBLR3CP+ and pCamBLR3CP-. Southern blot analysis with the GLRaV-3 CP gene as hybridization probe showed no signal for these plants, thus confirming the PCR results. PCR with bar gene specific primers showed no amplification of the bar gene in the plants infected with pCAMBIA 3301. The plants transformed with pCamBLR3CP+ and pCamBLR3CP- were also screened for the presence of the bar gene. Three of the eight plants tested showed amplification of the -560 bp bar gene. This result suggests that these plants were transformed with pCAMBIA 3301 (vector without the ligated GLRaV-3 CP gene) and not pCamBLR3CP+ or pCamBLR3CP- as had been expected. This project provides preliminary work for the subsequent transformation of grapevine with the GLRaV-3 CP gene, in an attempt to impart virus resistance.
AFRIKAANSE OPSOMMING: Wingerd rolblaar is een van die mees beskadigende virale siektes wat baie wingerd areas in die wêreld aantas. In Aantal verslae oor die afgelope jare het closterovirus partikels met wingerd rolblaar geassosieer. Tot hede, is agt serologiese onderskeibare closterovirusse geïsoleer vanuit geaffekteerde wingerde, waarvan wingerd rolblaar geassosieerde closterovirus-3 (GLRaV-3) die beste gekarakteriseerd is. Virus bestandheid in transgeniese plante gebaseer op die uitdrukking van gene afkomstig vanaf virusse, staan bekend as patogeen-afgeleide weerstand. Die virale kapsule protein (CP) geen vervaardig In strukturele protein wat verantwoordelik is vir die bedekking van die virus partikel. Dié geen was gebruik in die eerste demonstrasie van patogeen-afgeleide weerstand. Kapsuul protein-bemiddelde weerstand is tans die mees praktiese en algemene gebruikte metode om virus weerstand in plant gewasse te verkry. Die CP geen van In Suid Afrikaanse isolaat van GLRaV-3 geïnfekteerde wingerde is geïsoleer, gekloneer en die volgorde is bepaal. Dubbelstring RNA (dsRNA) was uit GLRaV-3 geïnfekteerde materiaal geëkstraheer en In hoë molekulêre gewig band van -18 kb is geïdentifiseer. Die dsRNA is gebruik as In templaat vir In omgekeerde transkripsie PKR saam met GLRaV-3 CP geen spesifieke inleiers vir die amplifikasie van die GLRaV-3 CP geen (975 bp). Die GLRaV-3 CP geen is gekloneer in die pGem®-T Easy vektor. Klone met die CP geen in die sin (pLR3CP+) en teensin (pLR3CP-) oriëntasies respektiewelik is verkry. Die volgorde wat verkry is vanuit hierdie twee klone dui op In 99.26 % ooreenstemming met die enigste ander GLRaV-3 CP geen volgorde wat beskikbaar is. Die GLRaV-3 CP geen is uit pLR3CP+ en pLR3CP- gesny en is gesubkloneer in In plant ekspressie vektor, pCAMBIA 3301 in die sin (pCamBLR3CP+) en teensin (pCamBLR3CP-) oriëntasies respektiewelik, wat die sin en teensin geen ekspressie in transgeniese plante in staat stel. Die GLRaV-3 CP geen was ook gesubkloneer vanaf pCamBLR3CP+ in In ander plant ekspressie vektor, pCAMBIA 2301 in die sin orientasie en is as pCVSLR3CP+ benoem. Hierdie drie konstruksies is aan Dr. M. Vivier (Instituut vir Wyn Biotegnologie, Stellenbosch) gegee vir wingerd transformasie eksperimente. Twee van hierdie konstruksies, pCamBLR3CP+ en pCamBLR3CP- asook pCAMBIA 3301 is gebruik om Nicotiana tabacum deur middel van Agrobacterium tumefaciens-bemiddelde transformasie te transformeer. Plante is geselekteer vir hul vermoë om die onkruiddoder, Basta, te weerstaan. Die teenwoordigheid van die plant selekteerbare merker geen, bar, op elke konstruksie lui tot dié weerstand. Die plante wat getransformeer is met pCamBLR3CP+ en pCamBLR3CP- is deur PKR saam met die GLRaV-3 CP geen spesifieke inleiers getoets, en geen amplifikasie van die GLRaV-3 CP geen is getoon nie. Southern blot analise met die GLRaV-3 CP geen as hibridisasie peiler het geen sein gewys vir hierdie plante nie, wat die PKR resultate bevestig. Die plante wat getransformeer is met pCAMBIA 3301 is deur PKR saam met die bar geen spesifieke inleiers getoets, en geen amplifikasie van die bar geen is getoon nie. Die plante wat getransformeer is met pCamBLR3CP+ en pCamBLR3CP- is ook getoets vir die teenwoordigheid vir die bar geen. Drie van die agt plante wat getoets is, het amplifikasie van die -560 bp bar geen getoon. Hierdie onverwagte resultate stel voor dat dié plante met pCAMBIA 3301 (vektor sonder die geligeerde GLRaV-3 CP geen) en nie met pCamBLR3CP+ en pCamBLR3CPgetransformeer is nie. Hierdie projek verskaf voorlopige werk vir die daaropvolgende transformasie van wingerd met die GLRaV-3 CP geen in 'n poging om virus bestandheid te verskaf.
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De, Ascensao Ana. "Isolation and characterisation of a polygalacturonase-inhibiting protein (PGIP) and its encoding gene from Vitis vinifera L." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52312.
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Thesis (PhD)--Stellenbosch University, 2001.ENGLISH ABSTRACT: Polygalacturonase-inhibiting proteins (PGIPs) are present in the cell walls of a variety of plant species. These proteins have been shown to specifically inhibit endopolygalacturonases (endo-PGs) secreted by invading fungal pathogens as part of the induced disease resistance mechanism of plants. This is the first report on the isolation and characterisation of a pgip gene from Vitis vinifera L., designated grapevine pgip1. A single open reading frame encoding a deduced polypeptide of 333 amino acids with a predicted molecular mass of 37.1 kOa and a calculated isoelectric point of 8.61 was identified from a 5.6 kb subgenomic fragment of V. vinifera cv Pinotage. Nucleotide and derived amino acid sequence analysis of grapevine pgip1 showed significant homology with other characterised PGIP encoding genes and revealed features characteristic of PGIPs found in several other plant families. Genomic DNA analysis showed that grapevine pgip1 belongs to a small multigene family in Vitis cultivars. From Northern blot analysis it was evident that expression of the PGIP family is both tissue- and developmental stage specific. The grapevine pgip1 was transiently expressed in Nicotiana benthamiana L. with potato virus X (PVX) as a vector. Grapevine PGIP1 isolated from crude protein extracts of PVX-infected N. benthamiana were tested and showed inhibitory activity against polygalacturonases (PGs) from Botrytis cinerea. Grapevine PGIPs have not previously been purified and characterised. Molecular analyses have confirmed that PGIPs are typically encoded by multigene families and that the inhibitor specificities and kinetics of the isolated proteins differ within and among species. In this study, two PGIP isomers from V. vinifera berries were isolated. The one isomer, designated PGIP-A, was partially purified and had a molecular mass of 39 kOa, whereas the other PGIP, designated PGIP-B, was purified and had a molecular mass of 42 kOa as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SOS-PAGE) and Western blot analysis. Both proteins were cell wall-bound. Enzymatic deglycosylation confirmed that PGIP-B is a glycosylated protein. Grapevine PGIP-A showed strong inhibitory activity against a homogeneous PG from Aspergillus niger and to a lesser extent against PG from Fusarium moniliforme, but was unable to interact with a crude PG preparation from B. cinerea. Grapevine PGIP-B was able to strongly inhibit PGs from B. cinerea as well as from Colletotrichum gleosporoides, yet showed no inhibition towards PG from A. niger. The grapevine pgip1 gene was expressed under the control of the Cauliflower mosaic virus (CaMV) 35S promoter in tobacco plants via Agrobacterium tumefaciensmediated transformation. Transgenic tobacco plants expressing the grapevine PGIP (gPGIP1) were used to demonstrate the effectiveness of this inhibitor against fungal PGs and to investigate whether gPGIP1 influences disease development. Northern blot analysis identified 19 transgenic plants expressing pgip1 transcript levels. Crude PGIP extracts from the transgenic tobacco plants inhibited PGs from B. cinerea and C. gleosporoides, but not PG from A. niger. Leaves from untransformed tobacco plants, from transgenic tobacco lines showing high and low PG inhibition, and from transgenic plants that did not express pgip1, were inoculated with B. cinerea. Transgenic leaves showed a reduction in the size of necrotic lesions of macerated tissues of approximately 45% relative to control and non-expressing transgenic leaves. The results from the heterologous expression of gPGIP1, together with the results from the protein purifications and inhibition studies, indicate that the isolated grapevine pgip1 gene encodes the isolated PGIP-B isomer. This work has ; established a good model system to study certain aspects of plant-pathogen interactions in grapevine. Heterologous expression of gPGIP1 has demonstrated that PGIP inhibition of fungal PGs slows disease development of B. cinerea in planta.
AFRIKAANSE OPSOMMING: Sien volteks vir opsomming
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Wann, Steven R. "In vitro isolation and propagation of mammatoxin-resistant aspen." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/5742.
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Vanstone, Vivien Alison. "The role of fungi and the root lesion nematode, Pratylenchus neglectus, in damaging wheat roots in South Australia." Title page, summary and contents only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phv281.pdf.
Full textAbstract:
Includes bibliographical references (leaves 265-296). Pathogens associated with root damage were investigated in the Murray Mallee region of South Australia over the 1987-1989 growing seasons. Occurence of fungal species and the root lesion nematode (Pratylenchus neglectus) was assessed, and related to the appearance and severity of symptoms on the roots. Field experiments were supplemented with innoculation tests in the glasshouse and laboratory.
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MacKenzie, Donald J. "Molecular characterization of potato virus S and genetic engineering of virus resistant plants." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30622.
Full textAbstract:
The sequence of 3553 nucleotides corresponding to the 3'-terminal region of potato virus S (PVS) has been determined from cloned cDNA. The sequence obtained contains six open reading frames with the potential to encode proteins of Mr 10,734, Mr 32,515, Mr 7,222, Mr 11,802, Mr 25,092 and at least Mr 41,052. The amino acid sequence of the 33K ORF has been confirmed to be that of the viral coat protein gene. The nucleotide sequence of this ORF was obtained from expression plasmids which were isolated by binding with a specific monoclonal antibody to PVS, and the expression of coat protein fusion products was verified by Western blots of bacterial cell lysates. The deduced amino acid sequence of a 70 amino acid portion from the central region of the PVS coat protein was 59% identical to the analogous region of potato virus X. In addition, the 7K, 12K and 25K ORF's displayed significant sequence homology with similar sized ORF's from a number of potexviruses. The partial 41K ORF was homologous with the C-terminal portion of the viral replicase proteins of potato virus X and white clover mosaic virus. While the biological functions of the 12K and 25K non-structural proteins coded for by PVS and members of the potexvirus group remain unknown, the 12K protein displays a hydropathicity profile consistent with a membrane associated protein and the 25K protein contains a conserved sequence motif found in a number of nucleoside triphosphate binding proteins. Members of the carlavirus group are distinguished from the potexviruses by the presence of a small [11K (PVS, potato virus M) - 16K (lily symptomless virus)] 3' terminal ORF which appears to contain a sequence motif similar to the 'zinc-finger' domain found in many nucleic acid binding proteins.
The coat protein gene from potato virus S (PVS) was introduced into Nicotiana debneyii tobacco as well as a commercial potato cultivar, 'Russet Burbank', by leaf disc transformation using Agrobacterium tumefaciens. Transgenic plants expressing the viral coat protein were highly resistant to subsequent infection following mechanical inoculation with the Andean or ME strains of PVS as indicated by a lack of accumulation of virus in the upper leaves. The coat protein mediated protection afforded by these transgenic plants was sufficient to prevent the accumulation of virus in the tissues of non-transformed 'Russet Burbank' shoots which had been grafted onto transgenic plants inoculated with PVS, and in reciprocal grafts, transgenic shoots accumulated less than 2% (6 weeks after grafting) of the concentration of PVS found in non-transformed shoots similarly grafted onto plants systemically infected with PVS. These transgenic plants also displayed a measure of resistance to inoculation with a related carlavirus from potato, potato virus M. In agreement with previous reports for plants expressing PVX coat protein, plants expressing PVS coat protein were also protected from inoculation with PVS RNA. These results provide further evidence that coat protein mediated protection for these two groups of viruses, which share similar genome organizations, may involve inhibition of some early event in infection, other than, or in addition to, virus uncoating.
Specific monoclonal antibodies were prepared against a C-terminal derived 18 kDa portion of the 25K protein of PVS expressed as an in-frame chimeric fusion protein with the glutathione S-transferase gene. The in vivo expression of this non-structural protein in virus infected tissue, as well as tissue from transgenic tobacco (var Xanthi-nc) engineered to contain the entire 25K gene, was verified by Western immunoblot labelling.Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
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Van, Eeden C. (Christiaan). "The construction of gene silencing transformation vectors for the introduction of multiple-virus resistance in grapevines." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/53764.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: Viruses are some of the most important pathogens of grapevines. There are no effective chemical treatments, and no grapevine- or other natural resistance genes have been discovered against grapevine infecting viruses. The primary method of grapevine virus control is prevention by biological indexing and molecular- and serological screening of rootstocks and scions before propagation. Due to the spread of grapevine viruses through insect vectors, and in the case of GRSPaV the absence of serological screening, these methods of virus control are not always effective. In the past several methods, from cross-protection to pathogen derived resistance (PDR), have been applied to induce plant virus resistance, but with inconsistent results. In recent years the application of post-transcriptional gene silencing (PTGS), a naturally occurring plant defense mechanism, to induce targeted virus resistance has achieved great success. The Waterhouse research group has designed plant transformation vectors that facilitate specific virus resistance through PTGS. The primary focus of this study was the production of virus specific transformation vectors for the introduction of grapevine virus resistance. The Waterhouse system has been successfully utilised for the construction of three transformation vectors with the pHannibal vector as backbone. Each vector contains homologous virus coat protein (CP) gene segments, cloned in a complementary conformation upstream and downstream of an intron sequence. The primary vector (pHann-SAScon) contains complementary CP gene segments of both GRSPaV and GLRaV-3 and was designed for the introduction of multiple-virus resistance. For the construction of the primary vector the GRSPaV CP gene was isolated from RSP infected grapevines. A clone of the GLRaV-3 CP gene was acquired. The second vector (pHann- LR3CPsas) contains complementary CP gene segments of GLRaV-3. The third vector (pHann-LR2CPsas) contains complementary CP gene segments of GLRaV-2. The cassette containing the complementary CP gene segments of both GRSPaV and GLRaV-3 was cloned into pART27 (pART27-HSAScon), and used to transform N tabacum cv. Petit Havana (SRI), through A. tumefaciens mediated transformation. Unfortunately potential transformants failed to regenerate on rooting media; hence no molecular tests were performed to confirm transformation. Once successful transformants are generated, infection with a recombinant virus vector (consisting of PYX, the GFP gene as screenable marker and the complementary CP gene segments of both GRSPaV and GLRaV-3) will be used to test for the efficacy of the vectors to induce resistance. A secondary aim was added to this project when a need was identified within the South African viticulture industry for GRSPaV specific antibodies to be used in serological screening. To facilitate future serological detection of GRSPaV, the CP gene was isolated and expressed with a bacterial expression system (pETI4b) within the E. coli BL2I(DE3)pLysS cell line. The expressed protein will be used to generate GRSPaV CP specific antibodies.
AFRIKAANSE OPSOMMING: Virusse is van die belangrikste patogene by wingerd. Daar bestaan geen effektiewe chemiese beheer nie, en geen wingerd- of ander natuurlike weerstandsgene teen wingerdvirusse is al ontdek nie. Die primêre metode van beheer t.o.v. wingerdvirusse is voorkoming deur biologiese indeksering, en molekulêre- en serologiese toetsing van onderstokke en entlote voor verspreiding. As gevolg van die verspreiding van wingerdvirusse deur insekvektore, en in die geval van GRSPa V die tekort aan serologiese toetsing, is dié metodes van virusbeheer nie altyd effektief nie. In die verlede is metodes soos kruis-beskerming en patogeen-afgeleide weerstand (PDR) gebruik om virusweerstand te induseer, maar met inkonsekwente resultate. In onlangse jare is post-transkripsionele geenonderdrukking (PTGS), 'n natuurlike plantbeskermingsmeganisme, met groot sukses toegepas om geteikende virusweerstand te induseer. Die Waterhouse-navorsingsgroep het planttransformasievektore ontwerp wat spesifieke virusweerstand induseer d.m.v. PTGS. Die vervaardiging van virus spesifieke tranformasievektore vir die indusering van wingerdvirusweerstand was die primêre doelwit van hierdie studie. Die Waterhouse-sisteem was gebruik vir die konstruksie van drie transformasievektore, met die pHannibal vektor as basis. Elke vektor bevat homoloë virus kapsiedproteïen (CP) geensegmente, gekloneer in 'n komplementêre vorm stroom-op en stroom-af van 'n intronvolgorde. Die primêre vektor (pHann-SAScon) bevat komplementêre CP geensegmente van beide GRSPaV en GLRaV-3, en was ontwerp vir die indusering van veelvoudige-virusweerstand. Die CP-geen van GRSPa V was vanuit RSP-geïnfekteerde wingerd geïsoleer, vir die konstruksie van die primêre vektor. 'n Kloon van die GLRa V-3 CP-geen was verkry. Die tweede vektor (pHann-LR3CPsas) bevat komplementêre CP geensegmente van GLRaV-3. Die derde vektor (pHann-LR2CPsas) bevat komplementêre CP geensegmente van GLRa V-2. Die kasset bestaande uit die komplementêre CP geensegmente van beide GRSPaV en GLRaV-3, was gekloneer in pART27 (pART27-HSAScon), en gebruik om N tabacum cv. Petit Havana (SRI) te transformeer d.m.v. A. tumefaciens bemiddelde transformasie. Ongelukkig het potensiële transformante nie geregenereer op bewortelingsmedia nie; gevolglik was geen molekulêre toetse gedoen om transformasie te bevestig nie. Na suksesvolle transformante gegenereer is, sal infeksie met 'n rekombinante-virusvektor (bestaande uit PYX, die GFP geen as waarneembare merker en die komplementêre CP geensegmente van beide GRSPa V en GLRa V-3) gebruik word om die effektiwiteit van die vektore as weerstandsinduseerders te toets. 'n Sekondêre doelwit is by die projek gevoeg toe 'n behoefte aan GRSPaV spesifieke teenliggame binne die Suid-Afrikaanse wynbedryf geïdentifiseer is, vir gebruik in serologiese toetsing. Om toekomstige serologiese toetsing van GRSPa V te bemiddel, was die CP-geen geïsoleer en in 'n bakteriële uitdrukkingsisteem (PETI4b) uitgedruk, in die E. coli BL21(DE3)pLysS sellyn. Die uitgedrukte proteïne sal gebruik word vir die vervaardiging van GRSPa V CP spesifieke antiliggame.
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Guillon, Christopher. "Systemic alteration of defense-related gene transcript levels in mycorrhizal bean plants infected with Rhizoctonia solani." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33767.
Full textAbstract:
A time course study was conducted to monitor disease development and expression of the defense-related genes phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and hydroxyproline-rich glycoprotein (HRGP) in bean (Phaseolus vulgaris L.) plants colonized by the arbuscular mycorrhizal (AM) fungus Glomus intraradices , and post-infected with the soil-borne pathogen Rhizoctonia solani. Pre-colonization of bean plants by the AM fungus did not significantly reduce the severity of rot symptoms. RNA blot analysis revealed a systemic increase in transcript levels of the four defense-related genes in response to R. solani infection. On the other hand, pre-colonization of bean plants with G. intraradices elicited no change in PAL, CHS and CHI transcripts, but an increase of HRGP transcripts in leaves was detected. A differential and systemic alteration in the expression of all four defense genes was observed in AM beans post-infected with R. solani. Depending on the time after infection with R. solani and the tissue examined, varying responses from stimulation, suppression, to no change in transcript levels were detected.
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Chen, Chunquan 1958. "Induced systemic resistance against Pythium aphanidermatum by plant growth-promoting rhizobacteria on cucumber (Cucumis sativus L.)." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35862.
Full textAbstract:
Cucumber root rot caused by Pythium aphanidermatum can be suppressed by introduced plant growth-promoting rhizobacteria (PGPR). Preliminary experiments clarified that this root disease could be suppressed by strains of Pseudomonas aureofaciens, P. corrugata, and P. fluorescens. To determine whether the mechanism was a systemic resistance induced by PGPR, a split root technique was employed on greenhouse cucumbers grown in soilless substrates. On the split roots, bacteria which were introduced into one side of the root were completely separated from pathogen challenged-inoculated roots-on the other side of the roots. Results from the series of experiments conducted with this design demonstrated that (i) the resistance against root rot induced by PGPR was systemic, (ii) germination of P. aphanidermatum zoospores was reduced in extracts from bacterized roots compared to non-treated control, and (iii) spread of Pythium mycelia was delayed and zoospore germination was inhibited on the distant induced root, compared to the non-bacterized control. Furthermore, enzyme analysis indicated that phenylalanine ammonia lyase, peroxidase and polyphenoloxidase increased on cucumber roots two days after they were bacterized with Pseudomonas strains 13 or 63--28. When the bacterized roots were challenged with P. aphanidermatum, these plant defense enzymes increased as the symptoms appeared, but this accumulation of enzymes was not any higher on roots induced with each of the Pseudomonas strains compared to the Pythium inoculated control. This enzyme stimulation was also systemically induced by PGPR or P. aphanidermatum on cucumber roots. The patterns of iso-peroxidase induced with the PGPR and P. aphanidermatum treatments were different. High levels of salicylic acid (SA) accumulated in bacteria-induced roots, as well as in pathogen-infected roots, which suggests that SA may be associated with cucumber resistance response. But exogenous application of SA did not induce any systemi
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Taylor, Sharyn Patricia. "The root lesion nematode, Pratylenchus neglectus, in field crops in South Australia." Title page, contents and summary only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09pht2462.pdf.
Full textAbstract:
Includes bibliographical references (leaves 241-25). Aims to evaluate sampling procedures; assess the extent and magnitude of yield loss caused by Pratylenchus neglectus; assess the population dynamics of Pratylenchus neglectus in cereals; determine whether resistance occurs in field crops; and, assess whether variation occurs between geographically isolated species of Pratylenchus neglectus
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O'Connell, Dean Michael, and n/a. "Plant-arthropod interactions : domatia and mites in the genus Coprosma (Rubiaceae)." University of Otago. Department of Botany, 2009. http://adt.otago.ac.nz./public/adt-NZDU20090807.160026.
Full textAbstract:
Plant-based defence mutualisms involve aspects of plant morphology that influence the performance of plant parasites, their natural enemies and trophic interactions. Leaf domatia, small indentations on the underside of leaves, can be structurally complex, and are often inhabited by potentially beneficial mites and other arthropods. Plant morphological traits such as domatia that enhance mutualistic relationships may result in increased plant growth rates, and reproductive success. New Zealand supports ~60 plant species that have domatia, the most speciose genus being Coprosma. The aim of this thesis was to examine factors that affect the production of leaf domatia and their relationship with foliar mite assemblages. The three main objectives of this thesis are: First, to investigate the production of foliar domatia and their susceptibility to limited resources, particularly to carbon availability. Second, to test if domatia are inducible structures during leaf ontogeny in the presence of foliar mites and/or fungi. Finally, to explore the effect of domatia availability on foliar mite assemblages on leaves with and without resident mites. This thesis tested the stated objectives using C. lucida, C. ciliata, C. foetidissima and C. rotundifolia, with a combination of field investigations and controlled manipulative experiments. The cost of domatia production was investigated using two field surveys and two controlled experiments. Under natural conditions the relationship between leaf morphology and domatia were measured in situ and across an altitudinal gradient. The experimental manipulations used carbon and nutrient stress, induced by temperature, light and fertilizer application. The second objective was experimentally tested under field conditions by manipulating foliar mites and fungal densities on C. rotundifolia. The third objective was investigated by manipulating domatia availability on C. lucida shrubs across three different vegetation types. Under field conditions, the number of domatia per leaf was associated with leaf morphology in C. lucida and C. foetidissima, but not C. rotundifolia. Foliar carbon showed a positive, but weak association with domatia production in C. foetidissima and C. ciliata. Altitudinal induced-carbon stress on domatia production was ambiguous. Domatia production in C. foetidissima was positively associated to altitude in field survey (1), and negatively associated in the second survey, with no correlation found between carbon and altitude. Experimental C. rotundifolia shrubs held under elevated night-time temperatures showed a 2.5 fold increase in respiration, a 34% to 91% decrease in daily carbon gain, and 38% decrease in domatia per leaf mass. Domatia production showed no significant differences under nutrient stress. The results showed little evidence to support a role for induction of domatia. Domatia production in new leaves was similar across all experimental treatments. Diverse vegetation types supported 60% higher mite species. Leaves with domatia supported ~22 to 66% higher mite densities, greater colonisation success and more diverse mite assemblages, than those without domatia. In the pastoral vegetation, the absence of predatory mites on experimental shrubs resulted in no differences in fungivorous mite densities regardless of domatia availability. Plant investment in foliar domatia appears associated with the number of available sites on the leaf under field conditions. The role of carbon availability during leaf ontogeny suggests a complex and highly variable association with domatia production. Domatia are constitutive defence structures that influence mite assemblages, mediating both beneficial and antagonistic relationships. This thesis concludes that domatia are in part, carbon-based non-inducible structures that influence mite assemblages, plant-mite and mite-mite interactions, and increase the probability of successful colonisation.
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Ntushelo, Khayalethu. "Comparative studies on genetic variability and fungicide resistance in Tapesia yallundae." Thesis, Stellenbosch : Stellenbosch University, 1998. http://hdl.handle.net/10019.1/55834.
Full textAbstract:
Thesis (MScAgric)--Stellenbosch University, 1998.ENGLISH ABSTRACT: Eyespot is an important disease of spring wheat (Triticum aestivum L.). Four species of Ramulispora are associated with this disease, of which Tapesia yallundae and T. acuformis. are common. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance in Tapesia yallundae. Each of the chapters treats specific but related topics. T. yallundae, which is the only species thus far reported from South Africa, has been associated with yield losses of up to 50%. To enable the implementation of more accurate and effective control measures, understanding the dynamics of reproduction and the genetics of the pathogen is of utmost importance. Of the many plant disease control measures such as cultural practices, sanitation, biological control, etc., fungicide application is the most commonly resorted to measure in eyespot control. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance of Tapesia yallzll7dae. Fungicide application, however, is not without problems. The pathogen can build up resistance to fungicides. The most commonly used fungicides in eyespot control include the benzimidazole carbendazim, triazoles such as flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol, fenbuconazole, triademinol, and the imidazole, prochloraz. Cases of resistance to the groups listed above have been reported. Frequent monitoring for resistance is thus crucial to prevent wastage of fungicide and unnecessary impregnantation of the environment with potentially ineffective chemicals. In chapter 2 of this thesis 300 isolates of T. yallundae from 15 fields were evaluated for resistance against carbendazim, flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol and fenbuconazole. These results indicated that to some triazoles, such as fenbuconazole, a high level of resistance was already present in field populations. In a sexually reproducing fungus such as T. yallundae, knowledge pertaining to its ability to pass resistance factors to offspring is equally important. Mating studies were, therefore, also conducted with parental strains that showed signs of triazole resistance. Three generations were subsequently tested for resistance to five triazoles, namely flusilazole, tebuconazole, propiconazole, bromuconazole and flutriafol. Results of this study showed variable sensitivity in progeny, which indicated quantitative inheritance of resistance to triazoles. Although the sexual stage has not yet been observed in the field in South Africa, this knowledge lays the foundation for the long-term understanding of the population dynamics of the fungus. The ability of a heterothallic ascomycete population to reproduce sexually is dependent on the availability of its two mating types, MATI-I and MATI-2, their distribution, and female fertility amongst other factors. In the UK. the teleomorph is commonly observed in the field, which is in contrast to the situation in South Africa, where it has only been induced in the laboratory. A comparative study between the South African and the UK. populations was therefore undertaken. Isolates representative of the two populations were mated with tester strains as both sperm recipients and as sperm donors. This allowed the percentage of hermaphrodites to be determined. No difference in terms of female fertility was observed between the South African and the UK. populations, with both populations showing low effective population numbers. These data suggested, therefore, that the teleomorph would also occur more frequently in South Africa if the climate was more indusive to its development. The overall results of this study indicated that eyes pot could still be controlled by means of fungicide application in South Africa. Although a shift in sensitivity was observed towards fenbuconazole and flusilazole, no resistance was detected towards carbendazim. The latter might be due to the absen<.:eof the sexual stage in the field, coupled by the monocyclic nature of the pathogen and sensible fungicide regimes. The absence of T. acujormis makes the disease situation less complicated in terms of fungicide application and management. Continuous surveys will have to be conducted, however, to monitor this situation in future.
AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die genetiese variasie, reproduksie dinamika en fungisied weerstand in Tapesia yallundae. Elke hoofstuk handel oor spesifieke maar verwante onderwerpe. Oogvlek is 'n belangrike siekte van lentekoring (Triticum aestivum L.). Vier spesies van Ramulispora word geassosieer met die siekte, waarvan Tapesia yallundae en T. acuformis mees algemeen voorkom. T. yallundae, wat tans die enigste spesie is wat in Suid-Afrika aangeteken is, het al verliese van tot 50% veroorsaak. Om meer akkurate en effektiewe beheermaatreels te implementeer, is dit noodsaaklik om die oorlewingsdinamika van die patogeen te verstaan. Van al die siektebeheermaatreels soos kulturele praktyke, sanitasie, biologiese beheer ens., bly fungisiedbehandeling die mees algemene maatreel vir die beheer van oogvlek. Fungisiedtoediening het egter ook verskeie probleme. Die patogeen kan weerstand opbou teen die fungisied. Die mees algemene fungisiedes wat vir oogvlekbeheer aangewend word sluit onder meer die benzimidasool karbendazim in, triasole soos flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol, fenbukonasool, triadimenol, en die imidasool, prochloraz. Weerstand is egter reeds teen hierdie middels bekend. Gedurige monitering vir weerstand is dus krities om die vermorsing van fungisied en besoedeling van die omgewing met oneffektiewe middels te beperk. In hoofstuk 2 van hierdie manuskrip word 300 isolate van T. yallundae van 15 lande geevalueer vir weerstand teenoor karbendazim, flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol en fenbukonasool. Resultate dui daarop dat teen sommige van hierdie triasole, soos bv. fenbukonasool, daar reeds 'n hoe vlak van weerstand teenwoordig was in veldpopulasies. In 'n seksueel reproduserende fungus soos T. yalluJ1dae, is dit noodsaaklik om te bepaal wat sy vermoe is om weerstandbiedenheid aan die nageslag oor te dra. Om die rede is paringstudies ook op ouers wat tekens van weerstand teenoor triasole getoon het uitgevoer. Drie generasies was gevolglik getoets vir weerstand teenoor vyf triasole, naamlik flusilasool, tebuconasool, propikonasool, brumukonasool en flutriafol. Resultate van die studie het 'n variasie in sensitiwiteit van die nageslag getoon, wat op 'n kwantitatiewe oorerwing van weerstand teen £riasole dui. Alhoewel die teleomorf nog nie in lande in Suid-Afrika opgemerk is nie, Ie hierdie kennis die fondament vir die langtermyn vertolking van die populasie dinamika van hierdie fungus. Die vermoe van 'n heterotalliese askomiseet populasie om seksueel voort te plant is afhanklik van die beskikbaarheid van sy twee paringstipes, MATI-I en MATl-2, hul verpreiding, vroulike vrugbaarheid en ander faktore. Alhoewel die teleomorf algemeen in lande in die Verenigde Koninkryk opgemerk word, is dit in kontras met die situasie in Suid-Afrika, waar hierdie stadium nog slegs in die laboratorium gelnduseer kon word. 'n Studie is dus onderneem om die Suid-Afrikaanse en V.K. populasies met mekaar te vergelyk. Isolate van die twee populasies is dus gepaar met paringsisolate as beide sperm ontvangers en sperm donors. Hierdie prosedure het dit moontlik gemaak om die persentasie hermafrodiete te bepaal. Geen verskille in vroulike fertiliteit is tussen die Suid-Afrikaanse en V.K. populasies bespeur nie, en beide populasies het ook 'n lae effektiewe populasie getal getoon. Hierdie data het dus voorgestel dat die teleomorf ook meer algemeen in Suid-Afrika sou voorkom as die klimaat meer geskik was vir teleomorf vormmg. Die resultate van hierdie studie het tot die slotsom gelei dat oogvlek steeds deur fungisiedbehandeling in Suid-Afrika beheer kan word. Alhoewel daar 'n merkbare verskuiwing in sensitiwiteit teenoor fenbukonasool en flusilasool was, was geen weerstand teenoor karbendazim waargeneem nie. Laasgenoemde kan dalk toegeskryf word aan die afwesigheid van die teleomorf in die veld, gekombineer met die monosikliese natuur van die patogeen en gebruik van alternerende fungisiedes. Die afwesigheid van T. acuformis maak die plaaslike siektetoestand minder gekompliseerd in terme van fungisied aanwending en bestuur. Voortdurende opnames sal egter uitgevoer moet word om hierdie situasie ook in die toekoms te monitor.
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"Comparative analysis of disease resistance related genes in rice." 2004. http://library.cuhk.edu.hk/record=b6073736.
Full textAbstract:
by Zeng Naiyan."December 2004."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (p. 185-213)
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
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Plett, JONATHAN. "Developmental Regulation of Cell Fate And Disease Resistance in Plants." Thesis, 2009. http://hdl.handle.net/1974/6139.
Full textAbstract:
Plant-wide communication between tissues and cells is organized, in part, by a suite of compounds called hormones. I have chosen to focus on the effects of one plant hormone, ethylene; how its synthesis is controlled and how its perception is mediated to differentially control cell development and response to pathogens.
In the production of ethylene, one level of control is by modulating the levels of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC). I characterize here a plant encoded gene homologous to bacterial ACC Deaminases, AtACD1, and show through up- and down-regulation of the gene that it can modulate the plants sensitivity to exogenous ACC. Once ethylene is produced, it is sensed in Arabidopsis thaliana by a family of 5 receptors. I show that ETR2 in Arabidopsis is responsible for modulation of the microtubule cytoskeleton assembly as loss-of –function mutations to this gene cause randomized microtubule assembly in trichomes and increase sensitivity to microtubule depolymerising drugs in root hairs. In studies of plant:pathogen interactions, ethylene is a central signaling agent required for plant resistance. While it has been shown that etr1 mutants show increased susceptibility to fungal pathogens, exogenous ethylene has also been shown to speed the progress of pathogenesis. Using Fumonisin B1 (FB1) to induce cell death I show that etr1-1 has accelerated cell death while ein4-1 has a reduced rate of necrosis. Further to this, mutations to the other three ethylene receptors do not have any effect on the rate of cell death.
My interest in cell development led to the characterization of an activation tagged Populus tremula x P. alba line with increased trichome initiation. The gene responsible for these phenotypes was identified as PtMYB186, which also affected growth rate, transpiration rate, photosynthetic capacity, and resistance to the Tussock moth larvae.
Together these studies provide a new framework for our understanding of how the ethylene signal is modulated in plants and the controls behind cellular development. This knowledge will help reconcile studies which show that ethylene has different effects on plant development and provide new avenues of research into trichome development.Thesis (Ph.D, Biology) -- Queen's University, 2009-01-13 10:08:03.605
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Soriano, Imelda Rizalina. "Novel inducible phytochemical defences against plant parasitic nematodes / Imelda Rizalina Soriano." Thesis, 2004. http://hdl.handle.net/2440/22121.
Full textAbstract:
"August 2004"Bibliography: leaves 146-169.
vi, 169 leaves : ill, (some col.), photos (col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004
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Coventry, Helen. "Induced defense responses in plants by bacterial lipopolysaccharides." Thesis, 2012. http://hdl.handle.net/10210/5911.
Full textAbstract:
M.Sc.Plant disease can be naturally suppressed by plant growth promoting rhizobacteria and endophytic / endorhizosphere bacteria. Apart from direct antagonism against pathogenic organisms, these plant growth promoting bacteria and endophytes can induce a form of systemic resistance (ISR) in plants. The main bacterial inducing component has been suggested to be the outer membrane lipopolysaccharides (LPS), found in the cell walls of Gramnegative bacteria. Burkholderia cepacia (Pseudomonas cepacia) is a bacterial endophyte that has potential as a biocontrol agent. Although a few studies have indicated that LPS from, certain Pseudorrionads has a protective effect in plants against disease, a controlled investigation has not been attempted previously with a purified preparation of LPS. LPS was isolated from the bacterial cell wall, prepared and characterized by denaturing electrophoresis. Characterization of the LPS also included the determination of 2-keto-3-deoxyoctonate, carbohydrate —, as well as the protein content. The purified LPS was found to possess activity as an elicitor of plant defence responses in tobacco where the induction of pathogenesisrelated (PR) proteins were investigated and electrophoretically analysed. An optimum LPS concentration range of 50-150 14/m1 was determined by studying cell death using the Evans blue procedure. Time and concentration ranges for LPS induced responses were established in cell suspensions, leaf discs, whole leaves and whole plants. It was determined that the PR-protein response could be optimally induced after four days following elicitation with 100 fag/ml LPS. Systemic induction of resistance was tested by treatment of the lower leaves and following the response in the upper leaves; as well as bacterial inoculation of the plant roots followed by PR-protein extraction of the leaves. Treatment of tobacco plants with LPS protected the plants against subsequent infection by the pathogen Phytophthora nicotianae, thereby suggesting a role for LPS as activators of systemic acquired resistance (SAR). It can be concluded from this study that the lipopolysaccharides from Burkholderia cepacia, that were used in this study, are effective local as well as systemic inducers of the defense PR-proteins in Nicotianae tabacum cv Samsun NN. The fact that protection is associated with PR-protein induction distinguishes it from the protection induced by rhizobacteria.
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Mienie, Charlotte Maria Susanna. "Towards marker assisted selection for nematode resistance in soybean." Thesis, 2000. http://hdl.handle.net/10413/10262.
Full textAbstract:
Meloidogyne javanica is the most widely spread nematode pest on soybean in South Africa. Only a few registered cultivars have some resistance to this nematode and there is an urgent need for an efficient breeding programme for resistant cultivars of all maturity groups. However, breeding is hampered by
laborious screening procedures for selection of resistant lines. The objective of this study was to develop an economically viable molecular marker system for application in selection procedures. Three techniques of marker identification were investigated, i.e. RAPD, RFLP and AFLP analysis. The RAPD technique proved to be applicable in fingerprinting soybean varieties, but was too sensitive for interplant variation to
be used as an efficient system for identification of molecular markers linked to nematode resistance. Both RFLP and AFLP screening identified markers linked to gall index variation in a segregating population of 60 F₂ progeny from across between a resistant cultivar, Gazelle, and a highly susceptible variety, Prima. A codominant RFLP marker( B212) was linked significantly to resistance and explained 62% of the variation in gall index. Seven AFLP markers were linked significantly to the resistance trait, of which four were linked in repulsion phase and three in coupling phase. All seven AFLP markers mapped to LG-F on the public soybean molecular map. The QTL for resistance mapped between markers E-ACC/M-CTC2 linked in coupling phase, 8212 and E-AAC/M-CAT1, linked in repulsion phase. These two AFLP markers bracketing the major resistance QTL were successfully converted to SCARs. Marker E-ACC/M-CTC2 was converted to a codominant SCAR marker SOJA6, which acounted for 41% of variation in gall index in the
mapping population. Marker E-AAC/M-CAT1 was converted to a dominant SCAR marker (SOJA7) and explained 42% of gall index variation in the mapping population. These two markers mapped approximately 3.8 cM and 2.4 cM respectively from the resistance QTL. This study represents the first report of the development of PCR-based sequence specific markers linked to resistance to M. javanica in soybean.Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2000.
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"Disease resistance related genes co-regulated in bacterial leaf blight near isogenic lines, Xa2, Xa12 and Xa14." 2004. http://library.cuhk.edu.hk/record=b5891981.
Full textAbstract:
Shuk-man Chow.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 171-186).
Abstracts in English and Chinese.
Thesis committee --- p.i
Statement --- p.ii
Abstract --- p.iii
Acknowledgement --- p.viii
General abbreviations --- p.x
Abbreviations of chemicals --- p.xi
List of figures --- p.xii
List of Tables --- p.xiii
Table of contents --- p.xv
Chapter 1. --- Literature review
Chapter 1.1. --- General introduction to rice disease --- p.1
Chapter 1.1.1. --- Pathogenesis of Bacterial Leaf Blight (BLB) --- p.1
Chapter 1.1.2. --- Pathogenesis of rice blast --- p.2
Chapter 1.1.3. --- Control of rice diseases --- p.3
Chapter 1.2. --- Plant defense mechanisms --- p.4
Chapter 1.2.1. --- Basal resistance in plants --- p.4
Chapter 1.2.2. --- Wound induced defense response --- p.5
Chapter 1.2.3. --- Pathogen induced host defense response --- p.6
Chapter 1.3. --- Structure of R gene products --- p.7
Chapter 1.4. --- Recognition between R and Avr proteins in rice --- p.8
Chapter 1.5 --- Current knowledge on Xa resistance and AvrXa avirulence protein --- p.9
Chapter 1.6 --- Current knowledge on Pi resistance and AvrPi avirulence protein --- p.10
Chapter 1.7 --- Pathogen induced signal transduction cascade --- p.12
Chapter 1.7.1. --- R gene mediated signal transduction cascade --- p.12
Chapter 1.7.2. --- Signal events of G-protein activation --- p.12
Chapter 1.7.3. --- Signaling events for the accumulation of Ca2+ in cytosol --- p.13
Chapter 1.7.4. --- Signaling events for oxidative burst --- p.14
Chapter 1.7.5. --- MAPK cascade in defense signaling --- p.15
Chapter 1.7.6. --- Transcriptional regulation of disease resistance related genes --- p.16
Chapter 1.7.7. --- Translational regulation of disease resistance related genes --- p.17
Chapter 1.8. --- Defense responses and defense related genes --- p.19
Chapter 1.8.1. --- Pathogenesis related (PR) proteins --- p.20
Chapter 1.8.2. --- Phytoalexins --- p.21
Chapter 1.9. --- Disease resistance related genes common between rice blast and BLB resistance --- p.22
Chapter 1.10. --- SA induced signal transduction pathway in rice --- p.23
Chapter 1.11. --- Important tools facilitating the identification of disease resistance related genes from BLB resistant rice lines --- p.24
Chapter 1.12. --- Hypothesis --- p.26
Chapter 1.13. --- Project objective --- p.26
Chapter 2. --- Materials and Methods --- p.27
Chapter 2.1. --- Plant Materials --- p.27
Chapter 2.2. --- Pathogen Inoculation --- p.27
Chapter 2.3. --- RNA extraction --- p.29
Chapter 2.4. --- Denaturing gel electrophoresis --- p.29
Chapter 2.5. --- Subtraction libraries construction --- p.30
Chapter 2.5.1. --- Cloning of disease resistance related genes --- p.32
Chapter 2.5.1.1. --- pBluescript II KS (+) T-vector preparation --- p.32
Chapter 2.5.1.2. --- Ligation --- p.32
Chapter 2.5.1.3. --- Transformation --- p.32
Chapter 2.5.1.4. --- Colony picking --- p.33
Chapter 2.5.1.5. --- PCR amplification of DNA inserts --- p.33
Chapter 2.5.1.6. --- Purification of PCR products --- p.34
Chapter 2.6. --- Gene chips printing --- p.34
Chapter 2.7. --- Probes synthesis and gene chips hybridization --- p.35
Chapter 2.8. --- Standard-RNAs synthesis --- p.35
Chapter 2.9. --- Data collection and analysis --- p.36
Chapter 2.10. --- Sequencing --- p.36
Chapter 2.11. --- cDNA synthesis --- p.37
Chapter 2.12. --- RT-PCR --- p.38
Chapter 2.13. --- DNA gel electrophoresis --- p.39
Chapter 3. --- Results --- p.58
Chapter 3.1. --- Construction of BLB gene chips --- p.58
Chapter 3.1.1. --- Preparation of cDNA clones for gene chips construction --- p.58
Chapter 3.1.2. --- Purification of PCR products on microtiter plate --- p.59
Chapter 3.1.3. --- Gene chips construction --- p.59
Chapter 3.1.4. --- DNA immobilization --- p.62
Chapter 3.1.5. --- Probe synthesis --- p.62
Chapter 3.1.6. --- Gene chip analysis --- p.65
Chapter 3.1.6.1. --- Scanning --- p.65
Chapter 3.1.6.2. --- Data analysis --- p.65
Chapter 3.2. --- "Identification of disease resistance related genes commonly regulated by Xa2, Xal2 and Xal4 BLB resistance loci" --- p.70
Chapter 3.2.1. --- "Signal perception, transduction and regulatory elements" --- p.71
Chapter 3.2.1.1. --- Proteins involved in reversible phosphorylation cascade --- p.71
Chapter 3.2.1.2. --- Proteins potentiate signal transduction through specific protein-protein interaction --- p.72
Chapter 3.2.1.3. --- Other signal transduction components --- p.73
Chapter 3.2.2. --- Transcriptional and translational regulatory elements --- p.74
Chapter 3.2.2.1. --- Proteins involved in transcriptional regulation --- p.74
Chapter 3.2.2.2. --- Proteins involved in post-transcriptional regulation --- p.75
Chapter 3.2.2.3. --- Proteins involved in translational regulation --- p.76
Chapter 3.2.3. --- "Oxidative burst, stress, apoptotic related genes" --- p.77
Chapter 3.2.3.1. --- Stress related proteins --- p.77
Chapter 3.2.3.2. --- Proteins involved in induction of oxidative burst --- p.78
Chapter 3.2.3.3. --- PR proteins --- p.79
Chapter 3.2.3.4. --- Proteolysis related proteins --- p.79
Chapter 3.2.4. --- Cell maintenance and metabolic genes --- p.80
Chapter 3.2.4.1. --- Antioxidant --- p.80
Chapter 3.2.4.2. --- Metabolic genes --- p.81
Chapter 3.2.4.3. --- Molecular chaperone --- p.82
Chapter 3.2.4.4. --- Cell cycle regulators --- p.82
Chapter 3.2.4.5. --- Cell wall maintenance --- p.83
Chapter 3.2.4.6. --- Proteins involved in protein transport --- p.83
Chapter 3.2.5. --- Unclassified/others --- p.84
Chapter 3.3. --- Expression analysis of disease resistance related genes --- p.88
Chapter 4. --- Discussion --- p.141
Chapter 4.1. --- Differential expression of disease resistance candidates --- p.141
Chapter 4.2. --- Disease resistance signal transduction components --- p.143
Chapter 4.2.1. --- Reversible phosphorylation cascade --- p.143
Chapter 4.2.2. --- Signal transduction potentiated by protein-protein interaction --- p.144
Chapter 4.3. --- Other signaling molecules --- p.145
Chapter 4.3.1. --- PRL1-interacting factor G --- p.145
Chapter 4.3.2. --- Vacuolar-type H+-ATPasen subunit G --- p.146
Chapter 4.4. --- Regulation of expression of disease resistance candidates --- p.146
Chapter 4.4.1. --- Transcriptional regulation of disease resistance related genes --- p.146
Chapter 4.4.1.1. --- G-box binding protein --- p.147
Chapter 4.4.1.2. --- MYB TF --- p.147
Chapter 4.4.2. --- Post-transcriptional modification of disease resistance candidates --- p.148
Chapter 4.4.2.1. --- RNA splicing factor --- p.148
Chapter 4.4.2.2. --- Glycine rich RNA binding proteins --- p.149
Chapter 4.4.3. --- Translational regulation of disease resistance related genes --- p.149
Chapter 4.5. --- Induction of oxidative burst --- p.150
Chapter 4.6. --- PR proteins --- p.151
Chapter 4.7. --- Cell maintenance --- p.152
Chapter 4.7.1. --- Protein folding --- p.152
Chapter 4.7.2. --- Protein degradation --- p.153
Chapter 4.7.3. --- ROS scavenging --- p.154
Chapter 4.7.4. --- Regulation of cell cycle --- p.154
Chapter 4.8. --- "Confirmation and profiling of disease resistance related candidates commonly regulated in Xa2, Xal2 and Xal4 BLB resistance NILs at different time points" --- p.155
Chapter 4.8.1. --- Basal resistance related genes --- p.156
Chapter 4.8.2. --- General disease resistance related genes --- p.161
Chapter 4.8.3. --- Pathogen responsive genes --- p.164
Chapter 4.8.4. --- Prediction of novel genes functions --- p.168
Chapter 4.9. --- Future prospect --- p.169
Chapter 4.10. --- Conclusion --- p.169
References --- p.171
Appendix --- p.187
36
Charity, Julia A. "Protective effects of two defence genes in transgenic plants." Phd thesis, 1996. http://hdl.handle.net/1885/146028.
Full text
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Arendse, Melanie Samantha. "Molecular cloning and analysis of a polygalacturonase-inhibiting protein (PGIP) gene from apple." Thesis, 2012. http://hdl.handle.net/10210/6316.
Full textAbstract:
M.Sc.Polygalacturonase-inhibiting proteins (PGIPs) are cell wall-associated plant proteins that inhibit endopolygalacturonases from phytopathogenic fungi. It has been proposed that pgip encoding genes could be utilised for engineering increased resistance in transgenic crops against important fungal pathogens such as Botrytis cinerea. During this study a pgip gene from Malus domestica cv Granny Smith apple fruit was cloned by the degenerate and inverse polymerase chain reaction (PCR) techniques. An alignment of the pear and bean PGIP sequences was used to design degenerate PCR primers in highly conserved regions. Degenerate PCR allowed the amplification of a 351bp internal fragment of the pgip gene, termed ipgip. The DNA sequence of ipgip was used to design inverse PCR primers. A Southern blot of apple genomic DNA probed with the ipgip fragment was used to identify restriction enzyme sites for inverse PCR. Inverse PCR enabled cloning of the remainder of the gene, from which a composite pgip gene sequence was constructed. The composite apple pgip gene comprised an open reading frame of 990bp that is predicted to encode a 330 amino acid polypeptide. The polypeptide contains a putative 24 amino acid N-terminal leader sequence that may function as a signal peptide for secretion. The deduced apple PGIP contains nine cysteine residues and seven potential N-linked glycosylation sites. Ten loosely conserved leucine-rich repeat motifs characteristic of PG1Ps were identified in the apple PGIP sequence. The apple PGIP showed 97% and 55% amino acid identity to the pear and bean PGIPs, respectively. The full-length apple pgip gene was re-isolated from genomic DNA by PCR using primers designed to the 5' and 3' ends of the composite pgip gene. The apple pgip gene was cloned into a plant transformation vector and transformed into tobacco by Agrobacterium-mediated transformation. Phenotypically normal transgenic tobacco plants were produced. Stable transgene insertion into the transgenic tobacco genomes was verified by PCR and Southern blot analyses. Sequence analysis of the pgip construct used for transformation revealed two potential mutations in the deduced amino acid sequence. The substitutions of Asp residues with Asn and Tyr at positions 43 and 196, respectively, could interfere with the secondary structure of the expressed transgene protein. To test whether the apple PGIP was effective against Botrytis cinerea, protein extracts were prepared from apple fruit and transgenic tobacco and tested for inhibitory activity against B. cinerea polygalacturonases. Biochemical assays showed that a heat-denaturable PGIP extract prepared from apple fruit inhibited the polygalacturonases produced by a virulent isolate of Botrytis cinerea grown on pectin and apple cell walls. Protein extracts prepared from transgenic tobacco did not show any inhibitory activity towards Botrytis polygalacturonases. This suggests the absence of active PGIP in the extracts possibly due to inefficient transcription of the transgene or due to the introduced mutations.
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"Biochemical characterization of the polygalacturonase inhibiting protein from cotton." Thesis, 2012. http://hdl.handle.net/10210/5529.
Full textAbstract:
M.Sc.Plants have evolved a complex array of biochemical pathways that enable them to recognise and respond to signals from the environment. At present, little is known about the signal transduction pathways that are activated during a plant's response to attack by a pathogen, although this knowledge is central to our understanding of disease susceptibily and resistance. A common form of plant resistance is the restriction of pathogen proliferation to a small zone surrounding the site of infection. In many cases, this restriction is accompanied by localized death of host tissues, known as the hypersensitive response. In addition to local defense responses, many plants respond to infection by activating defenses in uninfected parts of the plant. As a result, the entire plant is more resistant to a secondary infection. This systemic acquired resistance can persist for several weeks or more and often confers crossresistance to unrelated pathogens. Fungal polygalacturonases (PGs) catalyze the fragmentation and the solubilisation of the homogalacturonan in the plant cell wall. These enzymes might have important functions during plant colonization by a fungus. PGs have also been shown to activate plant defense responses, likely because they generate oligogalacturonides with elicitor activity from the plant cell wall. A polygalacturonase inhibiting protein (PGIP), found in the plant cell wall of many plants, forms a specific complex with fungal PGs and favours the accumulation of elicitor-active oligogalacturonides in vitro. An agarose diffusion assay was used to screen the extracts from Verticillium dahliae for PG activity and ensuing inhibition by purified cotton PGIP. Quantitative determination of differences in polygalacturonase activity in the extracts were performed using a reducing sugar assay. There may be more than one isoform of PG present since the polygalacturonases produced by fungi are likely to be to a mixture of exo- and endo-PGs. Polygalacturonase was therefore isolated from 18-day-old culture filtrates of V. dahliae. The enzyme was partially purified by means of ammonium sulphate precipitation and gel chromatography. The band responsible for PG activity was identified and characterized, having a molecular weight of approximately 28-31 kDa, and a pl of 5.1 - 5.9. Kinetic studies indicate a Km of 0.33% and V,„,,of 0.85 pmoles reducing units / min. A commercial preparation of endo-PG from Aspergillus niger was used as a control. This endo-PG had a molecular weight of 68 kDa and a pl point of 3.6 and 5.1, suggesting there were at least two isoforms of endo-PG present. Kinetic studies indicate a K m of 0.33% and V,,„ of 1.07 gmoles reducing units / min.
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Van, der Merwe Johannes Andreas. "Cloning and characterisation of the orfx gene from Nicotiana tabacum cells." Thesis, 2008. http://hdl.handle.net/10210/1221.
Full textAbstract:
M.Sc.As part of an investigation into differential gene expression in response to abiotic and chemical inducers of acquired resistance in tobacco, a PCR fragment of 660bp was repeatedly found in RNA preparations from treated cell suspensions by differential display analysis. The fragment (D1B) was isolated, purified, cloned and sequenced. The nucleotide sequence of the fragment was compared with sequences in the BLAST sequence database and was found to be homologous to the mitochondrial orfx genes from Arabidopsis thaliana, Beta vulgaris, Oenothera berteriana, Oryza sativa and Marchantia polymorpha. In order to obtain the full sequence of the gene specific primers were designed using the Arabidopsis sequence as template. The primers were designed to complete the 5’-end of the gene and were designed to overlap the D1B fragment previously found. A fragment (C3Y) of 460bp was isolated, purified, cloned and sequenced. The complete sequence (D1B and C3Y combined) was 851bp long and showed 96% homology with the Arabidopsis orfx gene on the nucleotide level and 87% homology on the translated amino acid level. The sequence was submitted to the Basic Local Alignment Search Tool (BLAST) database as accession gi: 24209907. In plant genomes, the orfx gene is closely linked to important structural genes such as the nad subunits of complex I (NADH: ubiquinone oxidoreductase). Orfx codes for a hypothetical protein that shows homology to the mttB (membrane targeting and translocation) gene found in E. coli. In bacteria the gene is essential because if deleted, the organism was no longer viable. Functional analysis of the bacterial gene revealed a novel pathway specific for membrane targeting and secretion of cofactor containing proteins, such as iron-sulphur (Fe-S) clusters, of which the mttB gene encodes one subunit. It is thought that a similar pathway might be responsible for the correct localisation and assembly of such Fe-S containing protein complexes in the inner mitochondrial membrane of higher plants. The differential display result may be indicative of a general up-regulation of mitochondrial gene expression in response to the triggering of plant defences or a possible specific effect on the expression of the orfx gene. A hypothesis was formulated that chemical inducers of plant defences affect the mitochondria of treated plant cells to result in increased production of reactive oxygen intermediates (ROI), similar to the oxidative microbursts proposed to be involved in systemic required resistance. Using a dichlorodihidrofluorescein (H2DCFDA) assay, it was found that salicylic acid (SA), benzo (1,2,3) thiadiazole-7-carbothioc acid S-methyl ester (BTH) and isonitrosoacetophenone (INAP) increased ROI production within cells in a dose dependant manner. The biochemical basis of this effect could possibly be related to the inhibition of the NADH:ubiquinone oxidoreductase activity of complex I of the mitochondrial electron transport chain by SA, BTH and INAP.
Prof. I.A. Dubery
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Lindbo, John A. "Virus resistance in transgenic plants expressing translatable and untranslatable forms of the tobacco etch virus coat protein gene sequence." Thesis, 1993. http://hdl.handle.net/1957/35627.
Full text
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Dias, Katia. "Evaluation of resistance to tomato curly stunt virus in tomato." Thesis, 2013. http://hdl.handle.net/10539/12342.
Full textAbstract:
Solanum lycopersicon (the cultivated tomato) is a commodity of great economic importance in South
Africa (SA) as well as worldwide. A destructive viral disease known as Tomato curly stunt virus,
ToCSV-[ZA:Ond:98], belonging to the genus Begomovirus has negatively impacted on tomato
production in SA. This has brought about the need to develop resistant cultivars to ToCSV. Since all
cultivated tomato cultivars are susceptible to ToCSV, resistance genes against the virus found in wild
tomato plant species have been introgressed into the cultivated tomato by plant breeding
techniques. Wild relatives of tomato were adapted to many pathogens (including viruses) as well as
stresses from the surrounding environment. During breeding for improved fruit quality and
increased yield, the gene networks giving rise to many biotic and abiotic stress resistances have been
lost leaving the domesticated tomato extremely susceptible. Plant breeders have reconstituted
some of the gene networks into the cultivated tomato that provide tolerance to stresses including
viruses. They have achieved this by the help of marker-assisted selection (MAS), where the
associated marker is used as an indirect selection criterion. This is an important process in
commercial breeding programs as it allows for a speedy selection of selected traits in the
development of tomato hybrids. The defence response to abiotic stresses in plants includes the
expression of heat shock proteins (HSPs) that function as stress response proteins, molecular
chaperones and proteases which repair or degrade damaged proteins.
The objective of this study was to elucidate the type of resistance mechanism of a tomato inbred
line (TAM), to ToCSV. Since TYLCV-IL shows 77% nucleotide identity with ToCSV, molecular markers
already established for the detection of resistance genes for TYLCV-IL were used to screen TAM.
The inbred line, TAM, was screened for the absence of any of the known resistant genes to TYLCV-IL
using molecular markers already established for the screening of TYCLV-IL resistance genes. TAM
was crossed with susceptible cultivar, Rooikhaki, to produce F1 hybrids. These F1 hybrids were
selfed to produce an F2 population. Infection trials using ToCSV were conducted using TAM inbred
line, F1 hybrids and the F2 population. Since TAM did not have any of the known resistance genes to
TYLCV-IL, a possible novel resistance source to ToCSV was speculated. A clue to the resistant
mechanism against ToCSV resistance in TAM was indicated by the segregation patterns of the F2
population after inoculation with ToCSV. The results suggest that the resistance is under the control
of partially dominant resistant genes. The level of resistance of commercial South African tomato cultivars (Tyler and Tovi-star) against
TYLCV-IL was investigated. The heat shock protein (HSP) profiles of these two SA lines including
susceptible cultivar, Rooikhaki, were treated with abiotic stresses (salt and heat) and results were
compared with a similar study conducted with TYCLV-IL resistant and susceptible tomato cultivars.
Heat shock protein 70 accumulation patterns were similar in that HSP70 was more stable in the
resistant cultivars throughout the application when abiotic stresses were applied to the SA resistant
and susceptible tomato cultivars as compared to Israel resistant and susceptible breeding lines. A
relation between infection severity and the pattern of HSP expression was found. A higher level of
HSP 70 in resistant tomato plants could contribute to a lower symptom severity phenotype.
42
Edmonds, Gareth John. "Investigating induced resistance in sugarcane." Thesis, 2013. http://hdl.handle.net/10413/11423.
Full textAbstract:
Five potential resistance-inducing chemicals were applied to two sugarcane varieties (N12 and N27) in a pot trial with the aim of inducing resistance to nematodes in naturally-infested soil. BION® (acibenzolar-S-methyl), methyl jasmonate, cis-jasmone and 2,6-dichloroisonicotinic acid (INA) were applied as a foliar spray and suSCon® maxi (imidacloprid) applied to the soil. All chemicals were tested at two rates and plants were sprayed one week prior to being harvested at 7, 9 and 11 weeks of age. Meloidogyne and Pratylenchus infestation of sett and shoot roots was determined at each harvest. The activity of four pathogenesis-related proteins was examined at 7, 9 and 11 weeks using separate assays, these enzymes where chitinase, β-1,3-glucanase, peroxidase and polyphenol oxidase. Methyl jasmonate treatment produced significant increases in β-1,3-glucanase, chitinase and peroxidase activity. All other elicitor treatments showed little difference in enzyme activity from the Control. The effect of each treatment on plant growth was examined by recording the dried root and shoot biomass of each plant. No significant differences were seen (p<0.05; Holm-Sidak test). However, root and shoot dried biomass was highest in the N12 variety treated by suSCon® maxi.
The infection of sugarcane with Ustilago scitaminea (sugarcane smut) is commonly identified visually by the presence of a smut whip. Identification of sugarcane smut infection can be determined prior to whip development by staining tissue sections with lactophenol cotton blue and examining plant tissues microscopically. This allows for a rapid determination of smut infection which can aid breeding programs. Smut infection is achieved in vitro by soaking sugarcane setts in smut spores collected from infected whips. Four methods of inoculation were examined. The method that most consistently caused infection involved allowing setts to germinate for 24 hours, before puncturing a bud with a toothpick, followed by submerging the sett in 1x10⁸ smut spores per mℓ. An elicitor of systemic acquired resistance called BION®, and an insecticide with resistance-inducing properties called Gaucho® (imidacloprid) were used as a sett soak treatments to induce resistance to sugarcane smut. The effect of each treatment at three concentrations on plant germination and growth was examined in the NCo376 variety. Smut spore germination on agar was examined in the presence of both treatments at three concentrations. Sugarcane setts were treated with a concentration that did not significantly reduce the germination of smut spores or sugarcane setts. Plants were infected with smut post treatment and allowed to grow for approximately one month until plants were between 8 and 10 cm in height. Smut infection was assessed by cutting longitudinal sections through the base of the shoot and staining each section with cotton blue lactophenol. Treatment with BION® and Gaucho® did not reduce smut infection.M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.
43
Barker, Claire Louise. "An Examination of the signalling capacity of the tomato Cf-9 disease resistance protein." Phd thesis, 2002. http://hdl.handle.net/1885/148656.
Full text
44
Kempster, Valerie Noel. "Soil microbes as potential control agents for plant-parasitic nematodes in pasture / by Valerie N. Kempster." Thesis, 2000. http://hdl.handle.net/2440/14767.
Full textAbstract:
Bibliography: leaves 108-152viii, 152 leaves : ill. ; 30 cm.
This study investigates the induction of resistance to the clover cyst nematode, Heterodera trifolii Goffart, an economic pest in white clover pastures that are a key to high milk yields in dairy cattle...it explores the potential of soil and rhizosphere bacteria to induce systemic resistance in white clover, Trifolium repens L. (summary)
Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000
45
Kempster, Valerie Noel. "Soil microbes as potential control agents for plant-parasitic nematodes in pasture / by Valerie N. Kempster." 2000. http://hdl.handle.net/2440/14767.
Full textAbstract:
Bibliography: leaves 108-152viii, 152 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This study investigates the induction of resistance to the clover cyst nematode, Heterodera trifolii Goffart, an economic pest in white clover pastures that are a key to high milk yields in dairy cattle...it explores the potential of soil and rhizosphere bacteria to induce systemic resistance in white clover, Trifolium repens L. (summary)
Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000
46
Pedler, Judith F. (Judith Fleur). "Resistance to take-all disease by Mn efficient wheat cultivars." 1994. http://web4.library.adelaide.edu.au/theses/09PH/09php371.pdf.
Full text
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Choe, Y. W. (Young Won). "DNA markers for cereal cyst nematode (Heterodera avenae Woll.) resistance gene in barley." 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phc545.pdf.
Full text
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Hughes, Peter A. "Mode of action and protective effects of small basic protein toxins in transgenic plants." Phd thesis, 1997. http://hdl.handle.net/1885/145680.
Full text
49
Farsi, Mohammad. "Genetic variation for tolerance and resistance to Pratylenchus neglectus / by Mohammed Farsi." Thesis, 1995. http://hdl.handle.net/2440/18625.
Full textAbstract:
Bibliography: leaves 318-347.ix, 347 [24] leaves : ill. (some col.) ; 30 cm.
A major problem in the production of agricultural crops including wheat, is the damage caused by destructive plant parasitic nematodes, among these the root lesion nematode (Pratylenchus spp.) The association of P. neglectus with fungi in ceraeal root disease has been reported. Infection is associated with leaf yellowing, which reduces plant photosynthesis and grain yield. In nematode infested soil, well fertilized crops are usually less affected.
Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1996?
50
Farsi, Mohammad. "Genetic variation for tolerance and resistance to Pratylenchus neglectus / by Mohammed Farsi." 1995. http://hdl.handle.net/2440/18625.
Full textAbstract:
Bibliography: leaves 318-347.ix, 347 [24] leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
A major problem in the production of agricultural crops including wheat, is the damage caused by destructive plant parasitic nematodes, among these the root lesion nematode (Pratylenchus spp.) The association of P. neglectus with fungi in ceraeal root disease has been reported. Infection is associated with leaf yellowing, which reduces plant photosynthesis and grain yield. In nematode infested soil, well fertilized crops are usually less affected.
Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1996?