Abstract Single cotton boll weight (BW) and seed index (SI, 100‐seed weight) are key determinants of lint and seed yield, yet their genetic basis remains poorly understood. Here, a stable interploidy introgression line with small boll from Gossypium arboreum in Gossypium hirsutum , NB298, was employed to map quantitative trait loci (QTLs) of BW and SI. A moderate/minor‐effect QTL on ChrA05 was preliminary mapped in the F 2 population of NB298 and TM‐1, with the phenotypic variation explained of 6.21% and 1.65% for BW and SI, respectively, named q(BW+SI)‐A05 . Sixteen simple sequence repeat and insertion and deletion (InDel) markers were further developed for genotyping of individuals in F 2 and F 3 populations. A total of seven QTLs for three yield‐related traits (BW, SI, and boll number per plant) were detected. Among them, stable QTLs for BW and SI were co‐located in the interval between InDel‐4353 and InDel‐4370 in both F 2 and F 3 populations, with a length of 1354.55 kb. Then, the substitution mapping method demonstrated the QTL was located in an interval of 468.155 kb between the markers of InDel‐4365 and InDel‐4373. Comparisons of BW and SI between introgression lines with/without the introgression fragment showed they were significantly different. Combined with the RNA‐seq of the ovules of 0, 3, and 5 days post anthesis, three differentially expressed genes were obtained and subjected to virus‐induced gene silencing and overexpressing in cotton and ectopic expression in Arabidopsis thaliana . The identification of OFP17 (where OFP is ovate family protein) provides a molecular target for manipulating seed and fruit size to enhance cotton yield.
Xu et al. (Sat,) studied this question.