Fine mapping of BhDDL4.1, a major gene controlling the regulation of the deeply lobed leaf trait in wax gourd (Benincasa hispida)

Lobed leaves are vital in the high-density cultivation and breeding of wax gourd (Benincasa hispida). Thus, determining the molecular mechanisms underlying the development of lobed leaves is important. To this end, this study aimed to resequence 105 recombinant inbred lines, constructed using the parental lines, GX-7 and my-1, to elucidate the molecular mechanisms underlying leaf development in wax gourd. Genes associated with lobed leaves in wax gourds were first evaluated via quantitative trait loci (QTL) mapping. Next, the F₂ population was expanded to 2000 plants for fine mapping and candidate gene analysis. Thus, the candidate area was reduced to 1.129 Mb, located between markers InDel980 and InDel853. Functional analyses of candidate genes were performed using gene functional annotation, coding sequence analyses, and expression analyses. Among 48 genes in the candidate region, only Bch04G012650 (termed BhDDL4.1) showed differences in expression between the two parents. Using sequence differences of previously screened candidate genes, an InDel marker (InDel623) was developed in BhDDL4.1 for molecular marker–assisted breeding of wax gourd; the accuracy rate was 74.03%. Our results indicate that BhDDL4.1 may play a key role in the regulation of the lobed leaf trait; thereby, we provide a theoretical basis for further exploration of the molecular mechanisms underlying the lobed leaf trait in wax gourd.