Identification of genetic loci for powdery mildew resistance in bread wheat

Powdery mildew is a very destructive disease that threatens yield and quality of wheat. In the present study, 262 recombinant inbred lines derived from a cross between Zhongmai 578 (ZM578) with moderate resistance to powdery mildew and Jimai 22 (JM22) with high resistance to powdery mildew in the field were used to map powdery mildew resistance loci using the high-density Illumina iSelect 50K single-nucleotide polymorphism array. Three quantitative trait loci (QTLs) on chromosomes 2B, 5B, and 5D were identified by inclusive composite interval mapping, designated as QPm.caas-2BL.1, QPm.caas-5BL, and QPm.caas-5DL, respectively, explaining 5.0%-37.0% of the phenotypic variances. The resistance allele of QPm.caas-5BL was contributed by ZM578, whereas alleles of QPm.caas-2BL.1 and QPm.caas-5DL were from JM22. QPm.caas-2BL.1, detected in all the six experimental environments, was a major and stable QTL. QPm.caas-5DL was detected in five of the six environments and is likely to be a new QTL for powdery mildew resistance. The kompetitive allele-specific PCR (KASP) markers Kpm-2BL and Kpm-5DL for QPm.caas-2BL.1 and QPm.caas-5DL, respectively, were validated in a diverse panel of 287 cultivars. These KASP markers, tightly linked with the QTLs, can be used for marker-assisted breeding targeting the improvement of powdery mildew resistance in wheat.