Development and identification of a novel wheat- Thinopyrum ponticum disomic substitution line DS5Ag(5D) with new genes conferring high resistance to powdery mildew and leaf rust

Abstract Powdery mildew and leaf rust are wheat diseases against which Th. Ponticum contains genes that confer resistance. Here, an elite wheat- Th. ponticum disomic substitution line DS5Ag(5D), which confers high resistance to both diseases, was developed and characterized in the Bainong Aikang58 (AK58) background, using genomic in situ hybridization (GISH), oligo-nucleotide probe multiplex fluorescence in situ hybridization (FISH) and molecular markers. There were 27 5Ag chromosome-specific molecular markers, of which 22 were co-dominant, confirming chromosome identification and SNP markers from the wheat 660 K SNP chip and providing molecular tools for tagging the alien chromosome. DS5Ag(5D) had higher resistance than its common wheat parents AK58 to powdery mildew throughout the growth period and leaf rust at the adult stage. Based on the resistance evaluation of DS5Ag(5D) and its parents, segregation analysis using five F 5 populations with different sensitive wheat backgrounds showed that the resistance genes mapped to 5Ag confer stable effects on the two diseases in different backgrounds. Resistance spectrum analysis combined with diagnostic marker detection of known resistance genes of Th. ponticum revealed that 5Ag contained two novel genes, Pm5Ag and Lr5Ag , which conferred resistance to powdery mildew and leaf rust, respectively. New elite germplasm and molecular markers for breeding wheat with powdery mildew and leaf rust resistance are provided in this study.