Field pathogenomics reveals the emergence of a diverse wheat yellow rust population

BACKGROUND: Emerging and re-emerging pathogens imperil public health and global food security. Responding to these threats requires improved surveillance and diagnostic systems. Despite their potential, genomic tools have not been readily applied to emerging or re-emerging plant pathogens such as the wheat yellow (stripe) rust pathogen Puccinia striiformis f. sp. tritici (PST). This is due largely to the obligate parasitic nature of PST, as culturing PST isolates for DNA extraction remains slow and tedious. RESULTS: To counteract the limitations associated with culturing PST, we developed and applied a field pathogenomics approach by transcriptome sequencing infected wheat leaves collected from the field in 2013. This enabled us to rapidly gain insights into this emerging pathogen population. We found that the PST population across the United Kingdom (UK) underwent a major shift in recent years. Population genetic structure analyses revealed four distinct lineages that correlated to the phenotypic groups determined through traditional pathology-based virulence assays. Furthermore, the genetic diversity between members of a single population cluster for all 2013 PST field samples was much higher than that displayed by historical UK isolates, revealing a more diverse population of PST. CONCLUSIONS: Our field pathogenomics approach uncovered a dramatic shift in the PST population in the UK, likely due to a recent introduction of a diverse set of exotic PST lineages. The methodology described herein accelerates genetic analysis of pathogen populations and circumvents the difficulties associated with obligate plant pathogens. In principle, this strategy can be widely applied to a variety of plant pathogens

Influência da nutrição mineral foliar sobre doenças da parte aérea da cultura do trigo

A utilização de fungicida para o controle de doenças foliares na cultura do trigo é prática comum entre os triticultores. Contudo, devido ao impacto ambiental provocado pelo seu uso generalizado, buscam-se alternativas para controle dos fitopatógenos. Sendo assim, este trabalho teve como objetivo avaliar o efeito da nutrição mineral foliar sobre as doenças foliares do trigo, bem como seu efeito sobre o desenvolvimento da planta. O delineamento experimental foi em blocos casualizados com quatro repetições e quatro tratamentos: 1- testemunha; 2- adubação foliar aos 30 dias após a emergência (DAE) e aos 75 DAE; 3- fungicida aos 30 e 75 DAE; e 4- adubação foliar aos 30 DAE e adubação foliar mais fungicida aos 75 DAE. Foram realizadas nove avaliações da incidência e da severidade do oídio, cujos dados foram utilizados para o cálculo das áreas abaixo das curvas de progresso da doença; três avaliações da severidade da ferrugem e da mancha da gluma; e duas avaliações da mancha amarela. Foram determinadas a massa de matéria fresca e seca da parte aérea e do sistema radicular e a produtividade da cultura. Foi observada redução da incidência e da severidade de oídio em função da adubação foliar, apenas na primeira avaliação de incidência e nas segunda e quinta avaliações de severidade da doença. O efeito complementar dos nutrientes com o fungicida para redução das doenças foi observado apenas para a mancha amarela, com redução de aproximadamente 11,16 % da severidade. Os maiores valores de produtividade foram observados para os tratamentos apenas com fungicida e, com fungicida mais nutrientes. A adubação foliar proporcionou aumento da massa fresca de raízes e massa seca de raízes. Apesar disso, não houve aumento da massa fresca da parte aérea em função da adubação foliar

Mapping and validation of QTL which confer partial resistance to broadly virulent post-2000 North American races of stripe rust in hexaploid wheat

A mapping population of 186 recombinant inbred lines developed from a cross between UC1110, an adapted California spring wheat, and PI610750, a synthetic derivative from CIMMYT’s Wide Cross Program, was evaluated for its response to current California races of stripe rust (Puccinia striiformis f. sp. tritici) in replicated field trials over four seasons (2007–2010) in the northern Sacramento Valley. A genetic map was constructed consisting of 1,494 polymorphic probes (SSRs, DArTs, and ESTs) mapped to 558 unique loci, and QTL analysis revealed the presence of four stripe rust resistance QTL segregating in this population, two from UC1110 (on chromosomes 3BS and 2BS) and two from PI610750 (5AL and 2AS). The two QTL of largest effects (on 3BS and 5AL) were validated in independent populations and their intervals narrowed to 2.5 and 5.3 cM, respectively. The 3BS QTL was shown, by allelism test and genotype, to carry a gene different from the Yr30/Sr2 complex. Mapped position also suggests that the 3BS QTL is associated with a gene different from either Yrns-B1 or YrRub, two stripe rust resistance genes mapped to this region in other studies. The 5AL QTL carries a previously unreported partial stripe rust resistance gene, designated here as Yr48. This paper discusses the individual contributions to resistance of these four QTL, their epistatic interactions, and their potential in durable resistance breeding strategies based on combinations of partial resistance genes

QTL analysis of pasta quality using a composite microsatellite and SNP map of durum wheat

Bright yellow color, firmness and low cooking loss are important factors for the production of good-quality pasta products. However, the genetic factors underlying those traits are still poorly understood. To fill this gap we developed a population of 93 recombinant inbred lines (RIL) from the cross between experimental line UC1113 (intermediate pasta quality) with the cultivar Kofa (excellent pasta quality). A total of 269 markers, including 23 SNP markers, were arranged on 14 linkage groups covering a total length of 2,140 cM. Samples from each RIL from five different environments were used for complete pasta quality testing and the results from each year were used for QTL analyses. The combined effect of different loci, environment and their interactions were analyzed using factorial ANOVAs for each trait. We identified major QTLs for pasta color on chromosomes 1B, 4B, 6A, 7A and 7B. The 4B QTL was linked to a polymorphic deletion in the Lpx-B1.1 lipoxygenase locus, suggesting that it was associated with pigment degradation during pasta processing. The 7B QTL for pasta color was linked to the Phytoene synthase 1 (Psy-B1) locus suggesting difference in pigment biosynthesis. QTLs affecting pasta firmness and cooking loss were detected on chromosomes 5A and 7B, and in both cases they were overlapping with QTL for grain protein content and wet gluten content. These last two parameters were highly correlated with pasta firmness (R > 0.71) and inversely correlated to cooking loss (R < -0.37). The location and effect of other QTLs affecting grain size and weight, gluten strength, mixing properties, and ash content are also discussed.Fil: Zhang, W.. University of California; Estados UnidosFil: Chao, S.. United States Department of Agriculture. Agricultural Research Service; Estados UnidosFil: Manthey, F.. North Dakota State University. Department of Plant Sciences; Estados UnidosFil: Chicaiza, O.. University of California; Estados UnidosFil: Brevis, J. C.. University of California; Estados UnidosFil: Echenique, Carmen Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Dubcovsky, J.. University of California; Estados Unido