Identification and Genetic Mapping of a Dominant Gene for Resistance to Powdery Mildew in Squash (Cucurbita pepo)

Powdery mildew (PM) is one of the most destructive pathogens that badly reduce the production of squash (Cucurbita pepo) all over the world. PM infection can significantly reduce squash yield up to 40 %. Developing resistant squash cultivars is the best approach to reduce the losses. So far, many  PM resistant genes have been described in squash, but none  have been mapped. This study was carried out to identify molecular makers linked to PM resistance in the squash inbred line ‘BS6’ which showed  high level PM resistance in our multiple year screening studies.  Inheritance analysis in F1, F2 and BC1 populations suggested that the resistance to PM race 2F in BS6 was conferred by a single dominant gene, which was designated as Pm-1. From bulked segregant analysis, two SSR markers SSR237 and SSR14 were identified flanking Pm-1 at at a genetic distance of 5.2 and 8.7 cM, respectively. The molecular makers identified here are useful in  in marker-assisted selection in squash breeding for  PM resistance, and for further cloning of the resistance gene.