Genetic mapping of locus and quantitative trait loci for angular leaf spot resistance in cucumber ( L.).

One of the most important cucumber diseases is bacterial angular leaf spot (ALS), whose increased occurrence in open-field production has been observed over the last years. To map ALS resistance genes, a recombinant inbred line (RIL) mapping population was developed from a narrow cross of cucumber line Gy14 carrying resistance gene and susceptible B10 line. Parental lines and RILs were tested under growth chamber conditions as well as in the field for angular leaf spot symptoms. Based on simple sequence repeat and DArTseq, genotyping a genetic map was constructed, which contained 717 loci in seven linkage groups, spanning 599.7 cM with 0.84 cM on average between markers. Monogenic inheritance of the lack of chlorotic halo around the lesions, which is typical for ALS resistance and related with the presence of recessive resistance gene, was confirmed. The locus was mapped on cucumber chromosome 5. Two major quantitative trait loci (QTL) . and . related to disease severity were found and located next to each other on chromosome 5; moreover, . was co-located with locus. Identified QTL were validated in the field experiment. Constructed genetic map and markers linked to ALS resistance loci are novel resources that can contribute to cucumber breeding programs.