The Distribution of Wks genes and Sequence Conservation of WKS1 in Wild Emmer Wheat Natural Populations

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most damaging diseases of wheat. The wheat gene Yr36 (WKS1), derived from wild emmer wheat (Triticum dicoccoides), confers partial resistance to a broad spectrum of stripe rust races at relatively high temperatures. The structure of this gene shows unique architecture with a kinase and putative START lipid-binding domains which are found only in the Triticeae tribe. We analyzed the distribution and the sequence variation of WKS1 in accessions from a broad ecogeographical range of wild emmer wheat natural populations. We found that the WKS1 gene is dispersed only in Israel, Jordan, Syria, and Lebanon, which are located at the Southern distribution range of wild emmer wheat natural populations. The distribution of WKS1 in Israel is mainly clustered in the Northern populations. Analysis of full length WKS1 (of more than 7 kb) from 47 wild emmer wheat accessions identified very low nucleotide diversity (π = 0.0002), with higher nucleotide polymorphism in the intron regions of WKS1 than in the coding regions. The coding region of WKS1 included four haplotypes among all tested accessions, encoding three different putative WKS1 proteins (designated P1, P2, and P3), as compared to the functional WKS1. Further stripe rust infection tests show that the putative WKS1 protein (P1) was identified in most of the partial resistant accessions. These results suggest that the WKS1 protein (P1) may be functional in conferring resistance to the stripe rust disease and can be utilized for wheat improvement.