Genome-wide mapping of resistance to stripe rust caused by Puccinia striiformis f. sp. tritici in hexaploid winter wheat

Abstract

Stripe rust, caused by the fungus Puccinia striiformis f. sp. tritici (Pst), is a widespread disease and major limit to wheat (Triticum aestivum L.) production worldwide. The USDA-ARS National Small Grains Germplasm Collection has proven to be a rich source of genetic diversity to improve stripe rust resistance in wheat breeding programs. The objective of the present study was to investigate the genetic diversity and sources of resistance to stripe rust in 441 accessions from the collection representing globally sourced winter wheat germplasm, as a complement to a previous study. A genome-wide association study was conducted to identify loci conferring resistance to Pst based on phenotypic data from four field experiments and greenhouse seedling resistance screening against three races of the pathogen. A total of 5831 single nucleotide polymorphism markers were used to investigate population structure, linkage disequilibrium, and marker–trait associations. Our results showed 12 and 7 genomic regions significantly associated with Pst resistance based on field adult-plant and greenhouse seedling responses, respectively, at a false discovery rate adjusted P value of <0.1. Four of the significantly associated genomic regions were mapped far from previously identified Pst resistance genes and quantitative trait loci, indicating that they represent potentially new Pst resistance loci. The present study provides additional insight into the usefulness of wheat germplasm collections as an important resistance source that can be used to incorporate diverse resistance genes into adapted wheat cultivars. Further work should aim to validate the identified genomic regions and the associated molecular markers to enhance their utility in marker-assisted breeding.