Characterization and diagnostic marker development for Yr28-rga1 conferring stripe rust resistance in wheat

Stripe rust is one of the most devastating wheat diseases and developing resistant cultivars is the most economical way to manage this disease. More than 80 stripe rust resistance genes (Yr genes) have formally been mapped. However, a lack of diagnostic markers has partially restricted the deployment of some resistance genes in molecular breeding. Among them, Yr28 showed high-temperature adult plant resistance (HT-APR) to stripe rust in the field, but it is rarely employed in wheat breeding. Here, Yr28-rga1 was found and isolated through the co-segregated marker mwg634 of Yr28. The gene sequence of Yr28-rga1-4A and Yr28-rga1-4B were almost the same between PI648511 and other wheat germplasm, including Chinese Spring (CS), Avocet, Yanzhan1, and Chuanyu12, but Yr28-rga1-4D showed only 88% identity between PI648511 and the others. Further, the high similarity in conserved domains to other wheat R proteins indicated that Yr28-RGA1 was a typical NBS-LRR protein. But the low identity in amino sequences also suggested that it was a novel gene. The specific 3-D protein structure in LRR regions also indicated that Yr28-rga1-4D from PI648511 might have different functional responses to disease. Furthermore, two gene-specific markers of cib-Yr28M1 and cib-Yr28M2 were developed for Yr28-rga1. Only 24 accessions showed identity to PI648511 on Yr28-rga1 locus in a panel of 672 wheat germplasms. The two diagnostic markers also revealed the positive correlation of Yr28-rga1 and stripe rust resistance (R2 > 0.8; p < 0.01) in field testing. These results indicated that the newly characterized Yr28-rga1 was a novel NBS-LRR gene conferring stripe rust resistance. The two diagnostic markers would be useful for marker assisted selection in wheat breeding against stripe rust.