Development and characterization of marker MBH1 simultaneously tagging genes Pm21 and PmV conferring resistance to powdery mildew in wheat.

Wheat-Haynaldia villosa translocations T6V#2S.6AL and T6V#4S.6DL, carriers of Pm21 and PmV, respectively, continue to contribute powdery mildew resistance in wheat varieties in China. Based on colinearity between Brachypodium distachyon and Triticeae species, genomic sequences from gene intervals of B. distachyon physically linked to a homolog of Stpk-V, a key part of Pm21, were used to design primers and screen for codominant and stable markers. An anonymous marker, MBH1, tagging both Pm21 in 6V#2S and PmV in 6V#4S was identified. It also distinguished wheat 6AS- and 6DS-derived homoeoalleles of MBH1. Sequence length comparisons showed a decreasing order of 6AS > 6DS > 6V#2S > 6V#4S. F2 segregation analyses were conducted on crosses Yangmai 18 (T6V#2S.6AL)/Yangmai 19 and Yangmai 16/Yangmai 22 (T6V#4S.6DL). MBH1 detected homozygosity of both Pm21 and PmV in segregating populations. The results also showed that T6V#2S.6AL is more transmittable than T6V#4S.6DL. Using MBH1, we reconfirmed the identities of powdery mildew resistance genes in Yangmai 21, Zhenmai 9, and Yangmai 97G59. The resistance donor to all three was T6V#2S.6AL, indicating that the published pedigrees were not correct. Pm21 in NAU419-Y15, an intercalary translocation carrying Pm21, was also tagged by MBH1. MBH1 is a broadly applicable marker for selecting and distinguishing the translocation chromosomes carrying Pm21 and PmV, which continue to be effective in China. [ABSTRACT FROM AUTHOR]