The first female flower node (FFFN) is a crucial trait affecting earliness and yield in bitter gourd (Momordica charantia L.). To identify the genetic locus and candidate gene controlling FFFN, we performed phenotypic and genetic analyses using two parental lines, ‘M144’ (average FFFN: 6.3 ± 2.0) and ‘K55’ (average FFFN: 22.0 ± 4.5), along with their F1 hybrid and an F2 population consisting of 317 individuals. The results show that the low FFFN trait was incompletely dominant over the high FFFN trait. Using BSA-seq, we mapped a FFFN locus to an interval of 18.8–22.5 Mb on chromosome 4. Fine mapping with KASP markers narrowed the McFFFN4.1 to a 73.05 kb interval between markers 25QP334 and 26QP20, which contained seven predicted genes. Transcriptome analysis revealed that only Moc04g29650, which is annotated as cytochrome b-c1 complex subunit Rieske, was differentially expressed between the parents within this mapping interval. Sequence comparison identified a single SNP (C > A) in the promoter region of Moc04g29650, which was located within a putative YAB1/FIL-binding motif. Given the known role of FILAMENTOUS FLOWER (FIL) in regulating floral transition in Arabidopsis thaliana, Moc04g29650 is proposed as the most likely candidate gene for McFFFN4.1. The KASP marker 26QP20, located near Moc04g29650, showed the strongest association with FFFN in the F2 population, with a maximum LOD score of 5.45, and thus represents a valuable tool for marker-assisted selection (MAS) breeding in bitter gourd. This study lays a foundation for cloning McFFFN4.1 and genetically improving early maturity in bitter gourd.
Liu et al. (Thu,) studied this question.