Genetic mapping of angular leaf spot resistance to Pseudomonas syringae pv. lachrymans in a Cucumis hystrix introgression line of cucumber

Abstract

Angular leaf spot (ALS), caused by Pseudomonas syringae pv. lachrymans, is a common and devastating bacterial disease of cucumber worldwide. However, to the best of our knowledge, the report on genetic mapping of ALS resistance in cucumber is relatively few. In this study, IL52, a Cucumis hystrix introgression line of cucumber, was identified to be resistant to ALS. To investigate the inheritance and genomic location of the ALS resistance gene, IL52 was crossed with a susceptible parent changchunmici (CCMC) to develop F1 plant and 155 F6 recombinant inbred lines (RILs). The F1 plant was susceptible to ALS. The segregation ratio of ALS disease resistance in 155 RILs was 80:75 resistance/susceptibility, fitting to 1:1. The results indicated that a single recessive locus psl-1 was responsible for conferring resistance to ALS in IL52. Further, psl-1 was mapped into the 3,118,855–3,951,558 bp interval of chromosome 1 by combining molecular mapping with bulked segregant analysis and next-generation sequencing (BSA-seq). The marker ALS-InDel was found to be closely linked with psl-1 through the genetic linkage analysis in the 18 resistant RILs, 18 susceptible RILs and 19 susceptible cucumber cultivars. This study on genetic mapping of ALS resistance gene in a Cucumis hystrix introgression line of cucumber will be helpful for fine mapping and marker-assisted selection of ALS resistance gene.