Natural variation in the promoter of FLOWERING LOCUS T-LIKE 2 in pumpkin (Cucurbita moschata Duch.) is associated with flowering time under short-day conditions

Late flowering is a serious bottleneck in pumpkin (Cucurbita moschata Duch.) agriculture production. Although key genes governing flowering time have been reported in many species, the regulatory network of flowering in pumpkin remains largely obscure, thereby impeding the resolution of industry-wide challenges associated with delayed fruit ripening in pumpkin cultivation. Here, we report an early flowering pumpkin germplasm accession (LXX-4). Using LXX-4 and a late flowering germplasm accession (HYM-9), we constructed an F-2 segregation population. A significant difference in FLOWERING LOCUS T-LIKE 2 (FTL2) expression level was identified to be the causal factor of the flowering time trait discrepancy in LXX-4 and HYM-9. Moreover, we have shown that a 21 bp InDel in the FTL2 promoter was the key reason for the waxing and waning of its transcript level. The 21 bp deletion excluded a repressor-AGL19 and recruited activators-BBX7, WRKY40 and SVP to the FTL2 promoter in LXX-4. Together, our data add a useful element to our knowledge which could be used to simplify breeding efforts for early-maturing pumpkin.