No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Nitric oxide (NO) is a key small molecule that orchestrates plant growth, development and immune function. The chief mechanism for the transfer of NO bioactivity is thought to be S-nitrosylation, the addition of an NO moiety to a protein cysteine thiol to form an S-nitrosothiol (SNO). The enzyme S-nitrosoglutathione reductase (GSNOR) indirectly controls the total levels of cellular S-nitrosylation, by turning over S-nitrosoglutathione (GSNO), the major cellular NO donor. In tomato (Solanum lycopersicum. L) a decrease in GSNOR expression, which is expected to increase the extent of cellular SNO formation, resulted in morphological phenotypes and disabled disease resistance. In contrast, increased GSNOR activity enhanced protection against an ordinarily virulent bacterial pathogen. Collectively, these results are similar to previous findings using the reference plant, Arabidopsis thaliana. Thus, the role of GSNOR may be highly conserved across the plant kingdom and manipulating the function of this protein may control important agricultural traits in crop plants.

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.

Numerous evidences showed that the resistance to syntenic fungal species Fusarium graminearum and Fusarium virguliforme infection in plants was partial, quantitative, and strongly influenced by environmental conditions. However, the molecular mechanisms underlying the resistance are still not fully understood. The objectives of this dissertation were to investigate the molecular mechanisms underlying the resistance in different plant species (mainly in maize, soybean, and Arabidopsis); identify and clone disease resistance genes; decipher their quantitative responses to Fusarial pathogens and mycotoxin deoxynivalenol (DON); identified genes that were transcriptionally regulated when the plants were treated with the pathogens and toxin. Methods were used to achieve these objectives including mapping, isolation, characterization, and functional analyses of genes implicated in disease resistance; analysis of microsynteny at their encoding loci; and identification of orthologs that might be associated with resistance to pathogen Fusaria across plant species etc. First, a maize gene that encoded a putative guanylyl cyclase-like protein (ZmGC1; EC 4.6.1.2) was characterized and shown to be associated with resistance to Gibberella ear rot caused by F. graminearum. The putative ZmGC1 amino acid sequence was 53% identical and 65% similar to AtGC1, one of the two Arabidopsis proteins known to possess an active and substrate specific guanylyl cyclase enzymatic function. Using a probe derived from the maize guanylyl cyclase-like gene (Zmgc1) to screen a recombinant inbred population developed from `CO387' (a partially resistant variety) X `CG62' (a partially susceptible variety), several polymorphic molecular markers were identified and four of them were significantly associated with Gibberella ear rot resistance in different environments. Polymorphisms were functional since the amount of Zmgc1 transcripts accumulating in ears increased more quickly and to a higher amount in the resistant genotype compared to the susceptible genotype after inoculation with F. graminearum. Furthermore, transcripts were responding to fungicidal activity when the maize seedlings (CO387) were treated with a fungicide, probenazole (3-allyloxy-1,2-benzothiazole-1,1-dioxide, PBZ). The transcript abundance (TA) of the maize Zmgc1 gene was increased more than 10 fold 8 hours after PBZ treatment. In contrast, the TA of Zmnbslrr1 (a NBS-LRR gene) transcript was significantly reduced in the Gibberella ear rot resistant genotype CO387 after the treatment with PBZ in the time-course study. Therefore, natural resistance and fungicide induced resistance may share common transcript abundance changes in maize plants. Second, to examine global effects of Fusarial pathogens on transcript abundance, cDNA microarrays from the model plant Arabidopsis thaliana were used. After Arabidopsis thaliana cv 'Columbia' was infested with Fusarium virguliforme, 168 transcripts were increased, nearly four times more than that of decreased. A. thaliana seedling growth was reduced by the pathogen in a proportional response to increasing spore concentrations. A set of putative resistance pathways involved in responding to the pathogen infection in A. thaliana was identified. Functional analyses of the orthologs of the responding genes between soybean and A. thaliana showed that the resistance responses had both common elements in some pathways (primary metabolism) and species specific differences in others (secondary metabolism). For example, the phenylpropanoid pathway response was different between the two species. In contrast to soybean, the phenylpropanoid pathway was not fully activated during the resistance response in Arabidopsis. Therefore, soybean and Arabidopsis did not share completely overlapping strategies in the specific pathways induced during resistance to F. virguliforme. Resistance to Fusarial toxins is a common mechanism for plant resistance. The mycotoxin deoxynivalenol (DON), produced by Gibberella zeae (the teleomorph of F. graminearum), was known to be both a virulence factor in the pathogenesis of wheat and an inhibitor of Arabidopsis seed germination. A. thaliana seedling growth was reduced by the toxin in a proportional response to increasing concentrations. A parallel comparison with a set of resistance pathways involved in response to the DON toxicity in A. thaliana was performed. The alterations of transcript abundances in the Arabidopsis plants treated with the toxin suggest that DON plays a significant role affecting the key primary metabolisms in Arabidopsis plants. The alterations ranged from the protein metabolism to redox production. New putative resistance pathways involved in responding to both pathogen and DON infestation in soybean and A. thaliana were described.

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.