Mapping of major Fusarium oxysporum resistance QTL fw8.1 and identification of candidate gene LsWAKL13 in bottle gourd

Bottle gourd fusarium wilt (FW), caused by Fusarium oxysporum f. sp. lagenariae (Fol), is a destructive soil-borne disease that severely impairs plant growth and reduces yields in bottle gourd production. Breeding FW-resistant varieties is the most sustainable management strategy, but the genetic underpinnings of resistance to FW in bottle gourd remain uncharacterized. To investigate the FW resistance genes, we first performed a genome-wide association study (GWAS) using a multiparent advanced generation intercross (MAGIC) population. Subsequently, we constructed a secondary population from FW-resistant line M238 and FW-susceptible line M363 within the MAGIC population, and further mapped FW resistance genes via quantitative trait loci sequencing (QTL-Seq) and linkage analysis. GWAS identified 83 significant single-nucleotide polymorphisms (SNPs) associated with FW resistance, primarily on chromosomes 3, 8, and 11. QTL-Seq identified two major QTLs (fw5.1 and fw8.1), and regional linkage mapping refined fw8.1 to a 264.4 kb interval containing 6 wall-associated kinase (WAK) family genes. Among these, LsWAKL13 was significantly upregulated in M238 vs. M363 after FW inoculation. A nonsynonymous G-to-T mutation in LsWAKL13 altered its 3D structure and correlated with FW resistance (lower disease index in M238-type allele accessions). Our findings identify LsWAKL13 as a causal candidate gene for FW resistance, while offering valuable genetic resources to speed up the breeding of resistant varieties.