Molecular Mapping of Loci Conferring Susceptibility to Spot Blotch and Resistance to Powdery Mildew in Barley Using the Sequencing-Based Genotyping Approach.

Spot blotch (SB) caused by and powdery mildew (PM) caused by f. sp. are two important diseases of barley. To map genetic loci controlling susceptibility and resistance to these diseases, a mapping population consisting of 138 recombinant inbred lines (RILs) was developed from the cross between Bowman and ND5883. A genetic map was constructed for the population with 852 unique single nucleotide polymorphism markers generated by sequencing-based genotyping. Bowman and ND5883 showed distinct infection responses at the seedling stage to two isolates (ND90Pr and ND85F) of and one isolate (Race I) of f. sp. . Genetic analysis of the RILs revealed that one major gene () controls susceptibility to isolate ND90Pr, and another major gene () confers resistance to f. sp. isolate Race I, respectively. was mapped on chromosome 1H of Bowman, as previously reported. was also mapped to the short arm of 1H, which was tightly linked but not allelic to the locus. Quantitative trait locus (QTL) analysis identified two QTLs, and , responsible for susceptibility to spot blotch caused by isolate ND85F in ND5883, which are located on chromosome 1H and 7H, respectively. was mapped to the same region as , whereas may represent a novel allele conferring seedling stage susceptibility to isolate ND85F. Identification and molecular mapping of the loci for SB susceptibility and PM resistance will facilitate development of barley cultivars with resistance to the diseases.