O objetivo deste trabalho foi avaliar a resistência parcial e a tolerância à ferrugem asiática, em sete cultivares comerciais e três linhagens de soja. Os ensaios foram conduzidos no município de Jataí, GO, no ano agrícola de 2005/2006. Ensaios distintos foram realizados para avaliação da resistência parcial e para avaliação da tolerância, todos repetidos em três épocas de plantio, a fim de se obter intensidade variável da doença em diferentes estádios fenológicos da cultura. Nos ensaios para avaliação da resistência parcial, o delineamento experimental foi o de blocos cazualizados com cinco repetições e cada parcela experimental foi composta por cinco linhas de seis metros de comprimento. A severidade da doença foi estimada em intervalos semanais, a partir do surgimento dos primeiros sintomas até a desfolha completa. Os dados foram analisados por meio de regressão não linear e o modelo logístico foi o que apresentou melhor ajuste. As curvas de progresso da doença para os cultivares EMGOPA-315, Luziânia, Pintado, Conquista, COODETEC-219 e para as linhagens 1, 2, e, 3 não apresentaram estabilização assintótica da severidade em função da desfolha precoce, ficando evidente apenas a fase exponencial de crescimento da doença. As epidemias apresentaram comportamento explosivo e foram muito semelhantes, demonstrando que esses genótipos foram igualmente susceptíveis ao patógeno. Os cultivares Tianá e EMGOPA-313 foram os únicos que apresentaram estabilização assintótica da severidade, em níveis muito abaixo de 1, o que evidenciou a presença de resistência parcial nesses cultivares. Nos ensaios para avaliação da tolerância, o delineamento experimental foi o de blocos casualizados com cinco repetições, com delineamento dos tratamentos em parcelas subdivididas. As parcelas (5 linhas de 12 m de comprimento) foram compostas pelos genótipos, e as subparcelas (5 linhas de 6 m de comprimento), pelo tratamento ou não com fungicida tebuconazole (0,5 L.ha-1) para controle da ferrugem. A severidade da doença foi estimada uma única vez e a tolerância foi avaliada pela análise estatística da diferença de produtividade, peso de mil grãos e de número de vagens e grãos por planta, entre subparcelas tratadas e não tratadas com fungicida, em cada época de plantio. Nenhum genótipo avaliado mostrou-se tolerante à ferrugem asiática da soja. / This work aimed the evaluation of partial resistance and tolerance to soybean asian rust on seven soybean genotypes and 3 lines. The research was conducted at Jataí, GO, during the growing season of 2005/2006. Experiments for partial resistance evaluation were carried out separately from experiments to evaluate tolerance, and in order to have different levels of disease severity, on different soybean growth stages, three trials for each experiment were carried out, each one with a different planting date during the season. Experiments for partial resistance evaluation were arranged on a randomized block design and each experimental unit was made by five soybean lines, 6 m long. The disease severity was estimate on week intervals from the first pustules appearance to the total defoliation. Analyses were done by non linear regression and the logistic model presented the best fitness to the observed data. The early defoliation on cultivars EMGOPA-315, Luziânia, Pintado, Conquista, COODETEC-219 and on lines 1, 2, e, 3 did not allowed the disease progress curves to reach asymptotical stabilization and for such genotypes, just the exponential part of the disease growth could be seen. Epidemics presented an explosive growth and the disease progress curves for such genotypes were similar, suggesting that they were similarly susceptible to the pathogen. The cultivars Tianá e E-313 were the only ones that presented asymptotical stabilization of disease and that happened on severity levels much smaller than 1, what was considered an evidence of partial resistance on those cultivars. Experiments conducted for tolerance evaluation were arranged in a split plot design with five replicates. The main plots (5 soybean rows, 12 m long) were composed by the soybean genotypes and the subplots (5 soybean rows, 6 m long) were those with or without fungicide (tebuconazole 500 mL.ha-1) application for rust control. Disease severity was estimate only once and tolerance was evaluated by the statistical analyses of difference of yield, thousand grain weight and pod and grain numbers, between treated and untreated subplots. None soybean genotypes analyzed presented tolerance to soybean asian rust.

Doctor of Philosophy / Genetics Interdepartmental Program / Allan K. Fritz / Wheat diseases cause significant economic losses every year. To ensure global food security, newly released cultivars must possess increased levels of broadly-effective resistance against wheat pathogens, acceptable end-use quality, and high yield potential. Genetic host resistance stands out from other management strategies as the most viable option for controlling diseases. New genotyping platforms allow whole genome marker discovery at a relatively low cost, favoring the identification of novel loci underlying traits of interest. The work presented here describes genomic approaches for mapping and predicting the resistance to Fusarium head blight (FHB) and wheat rusts. The first study used biparental mapping to identify quantitative trait loci (QTL) associated with Fusarium head blight (FHB) resistance. A doubled haploid population (DH) was originated from a cross of Everest and WB-Cedar, which are widely grown wheat cultivars in Kansas with moderately resistant and moderately susceptible reactions to FHB, respectively. We confirmed that neither of the parents carry known large-effect QTLs, suggesting that FHB resistance is native. Eight small-effect QTLs were identified as associated with multiple mechanisms of FHB resistance. All QTLs had additive effects, providing significant improvements in levels of resistance when they were found in combinations within DH lines. In the second study, a genome-wide association mapping (GWAS) and genomic selection (GS) models were applied for FHB resistance in a panel of 962 elite lines from the K-State Wheat Breeding Program. Significant single nucleotide polymorphisms (SNPs) associated with the percentage of symptomatic spikelets were identified but not reproducible across breeding panels tested in each year. Accuracy of predictions ranged from 0.25 to 0.51 depending on GS model, indicating that it can be a useful tool to increase levels of FHB resistance. GWAS and GS approaches were also applied to a historical dataset to identify loci underlying resistance to leaf and stem rust at seedling stage in a panel of elite winter wheat lines. Infection types of multiple races of wheat rusts from the last sixteen years of the Southern Regional Performance Nursery (SRPN) were used in this study. A total of 533 elite lines originating from several breeding programs were tested in the SRPN during this period of time. GWAS identified significant SNP-trait associations for wheat rusts, confirming the effectiveness of already known genes and revealing potentially novel loci associated with resistance.

Soybeans (Glycine max L.) are an important crop globally for its food, feed, and oilpurposes. It is impacted by many diseases, including Cercospora sojina, the causal agent of Frogeye Leaf Spot (FLS). Chemical and cultural controls to this fungal pathogen are insufficient, so genetic resistance must be acquired for adequate control. To this end, two recombinant inbred populations were screened in a greenhouse setting for their relative resistance to FLS, and their genomes were analyzed for contributing quantitative trait loci (QTL). In the Essex ́ Forrest population, one QTL was discovered on chromosome 13, and in the Forrest ́ Williams 82 population, two QTL were identified on chromosomes 6 and 11, respectively. These populations were then also screened in a field setting for agronomic traits. These traits were analyzed to detect one superior line for both FLS resistance and advanced agronomic traits, F ́W 125. This line should be used in future breeding projects to increase FLS resistance and reduce linkage drag for other desired characteristics.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22128号 / 農博第2374号 / 新制||農||1073(附属図書館) / 学位論文||R1||N5236(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 髙野 義孝, 教授 田中 千尋, 教授 寺内 良平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

No description available.

Soybean mosaic virus (SMV), has been the cause of numerous and often devastating disease epidemics, causing reduction in both the quality and quantity of soybeans worldwide. Two important genes for resistance to SMV are Rsv1 and Rsv4. Alleles at the Rsv1 locus have been shown to control resistance to all but the most virulent strain of SMV. This locus has been mapped previously to the soybean F linkage group. Rsv4 is an SMV resistance locus independent of Rsv1 and confers resistance to all strains of SMV. This locus has not been mapped previously. The purpose of this study is to investigate the two genomic regions that contain these vitally important resistance genes. A population of 281 F2 individuals that had previously been genotyped for reaction to SMV was evaluated in a mapping study which combined bulk segregant analysis with Amplified Fragment Length Polymorphism (AFLP). A Rsv4-linked marker, R4-1, was identified that mapped to soybean linkage group D1b using a reference mapping population. More than 40 markers were mapped in the Rsv4 segregating population including eleven markers surrounding Rsv4. This will provide the necessary framework for the fine mapping of this important genetic locus. Previous work has located Rsv1 to a genomic region containing several important resistance genes including Rps3, Rpg1, and Rpv. An RFLP probe, NBS5, whose sequence closely resembles that of several cloned plant disease resistance genes has been mapped to this chromosomal region. The efficacy of using this sequence to identify potential disease resistance genes was assessed by screening a cDNA library to uncover a candidate disease resistance gene which corresponds to this NBS5 sequence. Two related sequence classes were identified that correspond to NBS5. Interestingly, one class corresponds to a full length gene closely resembling other previously cloned disease resistance genes offering evidence that this NBS5-derived clone is a candidate disease resistance gene. A new marker technique was developed by combining the speed and efficiency of AFLP with DNA sequence information from cloned disease resistance genes. Using this strategy, three new markers tightly linked to Rsv1 were identified. One of these markers, which maps 0.6 cM away from Rsv1, has motifs consistent with other cloned disease resistance genes, providing evidence that this approach is an efficient method for targeting genomic regions where disease resistance genes are located. / Ph. D.

Soybean mosaic virus (SMV) and peanut mottle virus (PMV) are potyviruses that can cause serious yield reductions in soybean [Glycine max (L.) Merr.]. Virus resistant soybean cultivars have been released with alleles at the Rsv1 and Rpv1 locus that confer resistance to SMV and PMV, respectively. A high-resolution map-based cloning approach was undertaken to isolate Rsv1 and Rpv1 from soybean, with hopes of providing insight into this host-pathogen relationship. A mapping population of 1,056 F2 individuals was constructed from the cross of the resistant cultivar PI 96983 (Rsv1 and Rpv1) by the susceptible cultivar Lee 68 (rsv1 and rpv1). Ninety-one of the 1,056 F2 individuals had a cross-over (recombination) in the chromosomal region between microsatellite, or simple sequence repeat (SSR) marker loci Hsp176 and Sat120, and these 91 recombinant lines (RLs) were selected for further genetic analysis. Genotypes of Rsv1 and Rpv1 for the 91 RLs were obtained by inoculating their F2:3 progeny with SMV-G1 and PMV-P1, respectively. The 91 RLs also were used for mapping one random amplified polymorphic DNA (RAPD), five SSR, and 21 restriction fragment length polymorphism (RFLP) markers. Included in these RFLP markers were seven resistance gene candidate (RGC) and five resistance gene candidate flanking (RGCF) markers. RGC probes encode a protein with homology to previously cloned plant disease resistance genes, and RGCF probes are sequences obtained from the flanking regions of candidate disease resistance genes. The resultant high-resolution map consisted of 41 marker loci detected by 27 molecular markers. Rsv1 and Rpv1 cosegregated with one or more RFLP bands detected by RGCF probes: GG27-1a, 3gG2SP, and/or T3G. Analyses of the disease reaction and molecular marker data from seven RLs suggested that the map position of Rsv1 should be at a locus different from that designated by the linkage analysis software, Mapmaker 3.0. Compared to the other 89 RLs, a high percentage (>34%) of F3 plants grown from four of these seven RLs gave a necrotic reaction when inoculated with SMV-G1. From this evidence, we believed that another locus independent of Rsv1 was involved in PI 96983's response to SMV-G1. The two loci conferring resistance to SMV-G1 were designated Rsv1a and Rsv1b. / Master of Science

Soybean has become one of the most important crops to the United States, resulting in a need to improve its disease resistance. The objectives of this study were to 1) design primers and develop PCR-based markers from disease-related expressed sequence tags (ESTs) and resistance gene analogues (RGAs), 2) assess the utility of such markers by diversity analysis of 12 soybean parental lines, and 3) search for possible association of the markers with known disease resistance genes by constructing a linkage map. The diversity analysis will allow this study to determine how well each marker can distinguish genotypes in soybean. Identifying the location of our markers in the soybean genome with the linkage map, will allow those related to disease resistance to be selected. A total of 202 simple sequence length polymorphism (SSLP) markers were constructed using a set of 1218 disease-related ESTs. Furthermore, 22 markers were constructed using previously identified RGA sequences. Both sets of markers were able to detect polymorphism in the diversity analysis. Also, 48 of the SSLPs, five of the RGAs, and 150 molecular markers were used to construct a soybean linkage map using 114 recombinant inbred lines (RILs). Several markers mapped to chromosomal regions known to contain disease resistance genes. This study has created a framework map, which will be useful for identifying the location of resistance genes, marker-assisted selection for resistance, discovering novel resistance genes, and understanding genome organization of resistance pathways in soybean. An effective approach to develop "candidate gene" markers has been demonstrated. / Master of Science

3-Hydroxy-3-methylglutaryl CoA reductase (HMGR, EC 1.1.1.34) mediates the first regulatory step (HMG-CoA reduction to mevalonate) in isoprenoid biosynthesis. The tomato genome contains at least four differentially regulated hmg isogenes encoding HMGR. Functions of tomato hmg2 in defense responses were studied by promoter analyses of hmg2:GUS gene fusions, overexpression of hmg2 cDNA, and antisense inhibition of hmg1 and hmg2 in transgenic plants. Activity of the hmg2 promoter is developmentally regulated showing expression in seedling cotyledons and hypocotyls, in trichomes, and in reproductive tissues including pollen, stigmas, ovules, petals and mature seeds. hmg2:GUS activity is rapidly induced by wounding or in response to pathogenic viruses or bacteria. hmg2:GUS expression is localized to tissue surrounding lesions generated through interactions with either TMV or the bacterial pathogen, Erwinia carotovora subsp. carotovora (Ecc). Tomato hmg2 cDNA was cloned by PCR, expressed in E. coli to confirm its HMGR activity, inserted behind the double enhanced CaMV 35S promoter, and engineered into tobacco. Southern and northern analyses confirmed transformation and message expression. Enzyme activity was enhanced compared to nontransformed plants. Selected transgenic plants were significantly reduced for Ecc tissue maceration. The size of necrotic lesions induced by TMV was also significantly reduced compared to the nontransformed or vector controls. Thus, genetic manipulation of the rate-limiting step in a major defense pathway provides a novel strategy for enhancing disease resistance. We also generated transgenic tobacco and tomato containing antisense constructs for tomato hmg1 and hmg2 to study their effect on disease resistance. Full-length hmg2 and 5' regions of hmg1 or hmg2 were inserted in the antisense orientation behind a 35S promoter. Tomato expressing the full-length hmg2 antisense showed lower HMGR enzyme activity and were more susceptible to soft rot by Ecc than control plants. In contrast, expression of either antisense hmg/ or antisense hmg2 in the heterologous tobacco system resulted in plants with enhanced resistance to Ecc and reduced TMV lesion sizes. These results may indicate that antisense inhibition is non-specifically exerted on isogenes other than the defense-specific HMGR gene. / Ph. D.