Genome-wide identification of flowering time genes in cucurbit plants and revealed a gene ClGA2/KS associate with adaption and flowering of watermelon.

Watermelon (Citrullus lanatus) is one of the major cucurbit crop that cultivated all over the world. Adaptability and flowering time are important agronomic characteristics that influence the quality and yield of watermelon, however, the molecular basis underlying these traits were still unclear. In this study, we identified 166, 182, 178, and 279 flowering genes in watermelon, melon, cucumber and pumpkin, respectively, and found that a lot of genes in the photoperiodic, autonomous, and vernalization pathways were absence in the four cucurbits. A higher ratio of flowering time genes was identified in the hormone pathway in cucurbits than in Arabidopsis, and a higher average ka/ks value of hormone pathway genes than the photoperiodic and vernalization pathway genes was identified in watermelon. Moreover, a gene ClGA2/KS (Cla005482) were found to associated with ecotype differentiation, flowering time, and whole growth period in watermelon. This study added knowledge to the molecular basis of flowering time regulation in cucurbits, and the molecule marker of ClGA2/KS gene may facilitate the breeding progress for selecting watermelon varieties with superior adaption and flowering time.