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

Lobed leaves play a vital role in high-density cultivation and breeding of wax gourd. Thus, determining the molecular mechanisms underlying the development of lobed leaves is important. To this end, in this study, we 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 ( Benincasa hispida ). Genes associated with lobed leaves in wax gourds were first evaluated via quantitative trait loci (QTL) mapping. Next, the F2 population was expanded to 2,000 plants for fine mapping and candidate gene analyses. Thus, the candidate area is reduced to 1.129 Mb, located between the 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 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, and the accuracy rate was 74.03%. Our results indicate that BhDDL4.1 may play a key role in regulation of the lobed leaf trait; thereby, we provided a theoretical basis for further exploration of the molecular mechanisms underlying the lobed leaf trait in wax gourds.