Abstract
Key messageSNP-based genome scanning in worldwide domesticated emmer germplasm showed high genetic diversity, rapid linkage disequilibrium decay and 51 loci for stripe rust resistance, a large proportion of which were novel.Cultivated emmer wheat (Triticum turgidum ssp. dicoccum), one of the oldest domesticated crops in the world, is a potentially rich reservoir of variation for improvement of resistance/tolerance to biotic and abiotic stresses in wheat. Resistance to stripe rust (Puccinia striiformis f. sp. tritici) in emmer wheat has been under-investigated. Here, we employed genome-wide association (GWAS) mapping with a mixed linear model to dissect effective stripe rust resistance loci in a worldwide collection of 176 cultivated emmer wheat accessions. Adult plants were tested in six environments and seedlings were evaluated with five races from the United States and one from Italy under greenhouse conditions. Five accessions were resistant across all experiments. The panel was genotyped with the wheat 90,000 Illumina iSelect single nucleotide polymorphism (SNP) array and 5106 polymorphic SNP markers with mapped positions were obtained. A high level of genetic diversity and fast linkage disequilibrium decay were observed. In total, we identified 14 loci associated with field resistance in multiple environments. Thirty-seven loci were significantly associated with all-stage (seedling) resistance and six of them were effective against multiple races. Of the 51 total loci, 29 were mapped distantly from previously reported stripe rust resistance genes or quantitative trait loci and represent newly discovered resistance loci. Our results suggest that GWAS is an effective method for characterizing genes in cultivated emmer wheat and confirm that emmer wheat is a rich source of stripe rust resistance loci that can be used for wheat improvement.
Highlights
Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is a threat for wheat production in temperate areas throughout the world
Chromosome 1B and 2B had the largest number of markers, and higher genetic diversity and polymorphism information content (PIC) values than the genome-wide averages, while chromosome 3A had the smallest number of markers, and lower genetic diversity and PIC values
Our study reports the presence of valuable genetic variation for multiple Pst races in seedling tests and in field nurseries
Summary
Stripe rust (yellow rust) of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is a threat for wheat production in temperate areas throughout the world. Effective Yr resistance deployed in wheat varieties across most wheat growing regions of the world is needed to address the growing threat of stripe rust and minimize ongoing losses. Dicoccum), a self-pollinated allotetraploid species (2n = 4x = 28, AABB) with hulled grain, was one of the first crops domesticated in the world (Zohary and Hopf 2000). It was domesticated from wild emmer wheat Dicoccoides), which is the progenitor of the two widely cultivated wheat species: tetraploid durum wheat Despite the potential of emmer wheat to contribute novel alleles to wheat improvement, large collections of emmer wheat have been scarcely characterized using contemporary genomics resources and statistical genetics methods, which has hindered the exploitation of genetic variation in emmer wheat for cultivar improvement
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