Variation of flower opening and closing times in hybrids of evening flowering species Iris dichotoma and daytime flowering species Iris domestica

Different flowering and closing times within a diurnal period play a significant role in reproductive isolation. However, few studies focused on the genetics of flower opening and closing times within a day for the lack of suitable plant materials. Iris dichotoma opens in the afternoon and closes in the evening, while I. domestica opens in the early morning and closes at dusk. Moreover, they have overlapping flowering phenology and produce fertile hybrids, providing an extraordinary opportunity to study the genetics of flower opening and closing times within a day. To illuminate the genetic mechanism regulating flower opening and closing times, the flowering processes of I. dichotoma (Y), I. domestica (S), and their hybrids: F1, F2, F1 × S, Y × F1, (F1 × S) × F1 and F1 × (F1 × S) were observed. The results indicated that flower opening and closing times are controlled by different polygenes. For flower opening time, opening in the early morning as I. domestica is partial dominant to opening in the afternoon as I. dichotoma. For flower closing time, flower closure at dusk is dominant to closure in the evening.