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Spot blotch caused by the fungus Bipolaris sorokiniana poses a serious threat to bread wheat production in warm and humid wheat-growing regions of the world. Hence, the major objective of this study was to identify consistent genotyping-by-sequencing (GBS) markers associated with spot blotch resistance using genome-wide association mapping on a large set of 6,736 advanced bread wheat breeding lines from the International Maize and Wheat Improvement Center. These lines were phenotyped as seven panels at Agua Fria, Mexico between the 2013–2014 and 2019–2020 crop cycles. We identified 214 significant spot blotch associated GBS markers in all the panels, among which only 96 were significant in more than one panel, indicating a strong environmental effect on the trait and highlights the need for multiple phenotypic evaluations to identify lines with stable spot blotch resistance. The 96 consistent GBS markers were on chromosomes 1A, 1B, 1D, 2A, 3B, 4A, 5B, 5D, 6B, 7A, 7B, and 7D, including markers possibly linked to the Lr46 , Sb1 , Sb2 and Sb3 genes. We also report the association of the 2NS translocation from Aegilops ventricosa with spot blotch resistance in some environments. Moreover, the spot blotch favorable alleles at the 2NS translocation and two markers on chromosome 3BS (3B_2280114 and 3B_5601689) were associated with increased grain yield evaluated at several environments in Mexico and India, implying that selection for favorable alleles at these loci could enable simultaneous improvement for high grain yield and spot blotch resistance. Furthermore, a significant relationship between the percentage of favorable alleles in the lines and their spot blotch response was observed, which taken together with the multiple minor effect loci identified to be associated with spot blotch in this study, indicate quantitative genetic control of resistance. Overall, the results presented here have extended our knowledge on the genetic basis of spot blotch resistance in bread wheat and further efforts to improve genetic resistance to the disease are needed for reducing current and future losses under climate change. [ABSTRACT FROM AUTHOR]

Iranian wheat landrace accessions (IWAs) were collected from country‐wide farm fields and market places in 1935 by a professor at the University of Tehran and shared with University of California at Davis, California. IWAs were further submitted to the genebank of International Maize and Wheat Improvement Center (CIMMYT), Mexico. 2,403 IWAs from CIMMYT's genebank were assayed by DArT‐seq technology to assess genetic diversity. No apparent ecogeographic patterns related to genetic diversity were detected, probably due to long‐term transport and frequent interchange of landraces among farmers. A multivariate clustering procedure combining genotypic and phenotypic information was used in selecting a core‐set, which represented 15% of the hexaploid wheat accessions included in this study. This subset captured an estimated 93% of rare (frequency <0.05) alleles. Multisite phenotypic data (India, Mexico) validated the ability of the core‐set in detecting useful variants. Potential donor accessions for multiple traits (disease resistance, zinc concentration) were identified from the core‐set for wheat‐breeding. This report illustrates a breeder friendly robust core‐set formulation strategy for harnessing the useful genetic variation stored in the genebanks. [ABSTRACT FROM AUTHOR]

Wheat grain represents an important source of bioactive components that are associated with different health benefits, notably: dietary fibers, micronutrients and phytochemicals. However, despite the importance of these components, limited data are available on their content and composition, especially in durum wheat. In this study, 82 durum wheat landraces from Iran and Mexico were analyzed for arabinoxylan, iron, zinc, phytate and phenolic acids content. In general, wide variation was identified among landraces for these traits. Specifically, values ranging from 1.4 to 2.7% and 0.3–1.0% were detected for total and water-extractable arabinoxylans, respectively, in flour. In the case of micronutrients varied from 32.7 to 46.1 mg/kg (iron) and from 46.7 to 83.9 mg/kg (zinc) in grain. Phytate, a major component limiting micronutrient bioavailability, varied from 0.7 to 1.1% in whole-meal flour and the resulting phytate:iron and phytate:zinc molar ratios were 13.7–26.6 and 11.6–21.9, respectively, with more than 70% of the landraces exhibiting a relatively high Zn bioavailability. Seven phenolic acids were identified, with a variation in total phenolic acid concentration ranging from 279 μg/g to 845 μg/g in whole-meal flour. Overall, these results indicate that the landraces analyzed here could serve as useful genetic resources for the improvement of wheat nutritional quality in breeding programs. • Durum wheat landraces showed promisingly useful variability for nutritional traits. • Two landraces exhibited high total arabinoxylan content and good grain quality. • Several landraces had desirable Phytate:Zinc molar ratios. • Landraces are useful resources to improve nutritional quality in breeding programs. [ABSTRACT FROM AUTHOR]