Mapping of Powdery Mildew Resistance Genes and Mining of Candidate Genes in Bottle Gourd (Lagenaria siceraria) Based on BSA-seq and Transcriptome Sequencing

Powdery mildew is one of the most destructive fungal diseases of bottle gourd (Lagenaria siceraria), severely threatening yield and quality, yet the genetic basis of its resistance remains poorly understood. In this study, an F2 segregating population derived from a cross between the resistant inbred line G6 and the susceptible inbred line G3 was used, and BSA-seq, integrated RNA-seq analysis, qRT-PCR validation, and KASP marker development were comprehensively employed. SNP-index and InDel-index analyses independently mapped and converged on a candidate interval of 1,898,234–8,241,294 bp (~6.34 Mb) on chromosome 2. By comparing differentially expressed genes (DEGs) at 12, 24, 48, and 72 h post-inoculation with the BSA candidate interval, one candidate resistance gene, Lsi02G006660, was identified, and a KASP marker (Chr2_5941698, G/T) was successfully developed. This study provides a candidate gene and marker resources for molecular breeding of powdery mildew resistance in bottle gourd.