QTL Analysis of Fruit Shape in Bitter Gourd (Momordica charantia L.) Based on BSA and Linkage Mapping

Bitter gourd (Momordica charantia L.) is one of the most valuable crops in the Cucurbitaceae family.Fruit shape significantly impacts the appearance, quality, and commercial value of bitter gourd.This work investigated the genetic basis of the shape of bitter gourd fruit by analyzing fruit shape inheritance using a mixed major gene plus polygenes inheritance model.QTL analysis of fruit shape was conducted using BSA mapping combined with linkage mapping with an F 2 population from a cross between 'K44' (a stick-shaped inbred line) and 'Tan' (a conical-shaped inbred line).Genetic analysis revealed that the genetic model 1MG-NCD (a single pair of a negatively complete dominant major gene) was the best fit for the fruit shape index, with the major gene heritable rate at 39.56%.BSA mapping revealed three genetic loci regulating fruit shape on chromosomes MC01 (FS1.1),MC03 (FS3.1), and MC07 (FS7.1).Linkage mapping revealed one QTL each linked to fruit length (qFL1.1),fruit diameter (qFD1.1),fruit shape index (qFSI1.1),and fruit shape (qFS1.1).These findings led to the discovery of a consensus and major-effect QTL qMcFS1.1 on chromosome MC01, which was then mapped to a 452.63 kb interval.This underlying major-effect QTL will lay a solid foundation for the fine mapping and cloning of this locus for fruit shape in bitter gourds.