Molecular mapping of genes Yr64 and Yr65 for stripe rust resistance in hexaploid derivatives of durum wheat accessions PI 331260 and PI 480016.

KEY MESSAGE: This manuscript reports two new genes ( Yr64 and Yr65 ) for effective resistance to stripe rust and usefulness of their flanking SSR markers for marker-assisted selection. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat worldwide and resistance is the best control strategy. Durum wheat accessions PI 331260 and PI 480016 were resistant to all tested Pst races. To transfer the resistance genes to common wheat and map them to wheat chromosomes, both accessions were crossed with the stripe rust-susceptible spring wheat 'Avocet S'. Resistant F3 plants with 42 chromosomes were selected cytologically and by rust phenotype. A single dominant gene for resistance was identified in segregating F4 lines from each cross. F6 populations for each cross were developed from single F5 plants and used for genetic mapping. Different genes from PI 331260 and PI 480016 were mapped to different loci in chromosome 1BS using simple sequence repeat markers. The gene from PI 331260 was flanked by Xgwm413 and Xgdm33 in bin 1BS9-0.84-1.06 at genetic distances of 3.5 and 2.0 cM; and the gene from PI 480016 was flanked by Xgwm18 and Xgwm11 in chromosome bin C-1BS10-0.50 at 1.2 and 2.1 cM, respectively. Chromosomal locations and race and allelism tests indicated that the two genes are different from previously reported stripe rust resistance genes, and therefore are named as Yr64 from PI 331260 and Yr65 from PI 480016. These genes and their flanking markers, and selected common wheat lines with the genes should be valuable for diversifying resistance genes used in breeding wheat cultivars with stripe rust resistance.