Identification and Fine Mapping of Gummy Stem Blight Resistance Gene Gsb-7(t) in Melon

Gummy stem blight (GSB), caused by , is a devastating fungal disease of melon worldwide. Breeding GSB-resistant cultivars with host resistance genes is considered the most economic and effective strategy to control this disease. In this study, 260 melon germplasm resources were screened for resistance to GSB, and an inbred line, H55R, that exhibited immunity to GSB was identified. To further understand the resistance mechanism of H55R against GSB, an F population was obtained from a cross between the GSB-susceptible line A15 and H55R, and genetic analysis indicated that the GSB resistance in H55R was controlled by a single dominant gene, tentatively named . The gene was finally delimited to a 140-kb interval on chromosome 7 using bulked segregant analysis and chromosome walking strategies. Ten putative genes were annotated in this region that contains a wall-associated receptor kinase (WAK) gene . The gene contains two alternative transcripts, and , with five and seven nonsynonymous mutation sites, respectively. Gene expression analysis showed that expression of but not was significantly induced by at 24 h postinoculation, indicating that the transcript of was the most likely candidate gene of Our results offer new genetic resources and will be helpful for the development of GSB-resistant melon cultivars in the future.