Molecular mapping of a recessive stripe rust resistance gene yrMY37 in Chinese wheat cultivar Mianmai 37

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.) in many cool and temperate regions of the world. Resistant cultivars are the most effective, economical and environmentally friendly means of controlling the disease. Chinese wheat cultivar Mianmai 37 is resistant at all growth stages to all prevalent Chinese Pst races including v26, a new Pst race virulent to resistance genes Yr24/Yr26. Genetic analysis of the F1, F2 and F2:3 populations from a cross between Mianmai 37 and susceptible line Mingxian 169 indicated that resistance to Pst race v26 was conferred by a single recessive gene, temporarily designated yrMY37. Simple sequence repeat (SSR) marker analysis placed yrMY37 on chromosome 7BL near the centromere. Eight co-dominant genomic SSR markers, Xgwm400, Xwmc758, Xwmc476, Xgwm297, Xbarc267, Xwmc364, Xwmc696 and Xwmc396, were linked with yrMY37. The closest SSR loci Xbarc267 and Xgwm297 flanked the resistance gene at 0.38 and 0.78 cM, respectively. A seedling test with 22 Pst races indicated that the reaction patterns of Mianmai 37 were different from those of lines carrying resistance genes Yr2, Yr6, Yr67 and YrZH84 on chromosome 7B. As there is no recessive stripe rust resistance gene reported on 7BL so far, we believe that yrMY37 is most likely a new stripe rust resistance gene.