Genome-Wide Association Study of Powdery Mildew Resistance in Russian Spring Wheat (T. aestivum L.) Varieties

Abstract

Powdery mildew caused by the fungal pathogen Blumeria graminis f. sp. tritici (Bgt) is an econo-mically important disease of common wheat T. aestivum L. One of the most effective and environmentally important ways of protection of wheat against Bgt is cultivation of the varieties with genetic resistance. The aim of this work was to study the genetic diversity of Russian spring wheat varieties for the powdery mildew resistance loci. Phytopathological evaluation of 97 wheat varieties showed that no more than 10% of the varieties have low level of susceptibility to the Bgt population specific to the Western Siberian region. Association mapping carried out on the basis of SNP genotyping and phytopathological testing during three environmental seasons identified eight loci in chromosomes 1AL, 1DS, 2BL, 5AS, 5DS, 6AL, 6DL, and 7AL. A high impact to the phenotypic manifestation of the trait was established for genetic factors localized in chromosomes 5AS, 6AL, and 6DL. The long arm of chromosome 6D contains the gene Pm6Ai=2, which was introduced from wheatgrass Thinopyrum intermedium and provides effective protection against the powdery mildew pathogen. On the basis of comparative analysis of the chromosomal localization of the known Pm resistance genes and loci mapped in this work, it was assumed that QTLs in chromosomes 1DS, 5AS, and 6AL are novel, not previously described resistance loci. The obtained results can be used in breeding programs for selection of target loci and for development of molecular markers specific to Bgt resistance loci.