Populational change in flowering time caused by different harvesting date observed in a late-summer type cultivar Miyazakizairai of buckwheat (Fagopyrum esculentum Moench)

Buckwheat (Fagopyrum esculentum MOENCH) which is an entomophilous and cross-pollinated crop, can be classified into two ecotypes in a broad sense ; summer and late-summer types. The summer type cultivars are generally non-sensitive to day length, whereas the late-summer type cultivars are sensitive to short day. The former is assumed to have differentiated from the latter. In the previous paper (Minami and Namai 1986), we demonstrated that the late-summer type cultivars in the Kyushu region (low latitude ; 31-34 have a considerably wide potential for genetic variation from early to late flowering in the long day summer season as well as a potential capacity to differentiate to the summer type cultivars. In the present paper, we clarified the process of differentiation of the summer type cultivars from the late-summer type cultivars through ecological genetlc studies dealing with the effects of mass selection and harvesting date on the genetic structure of the flowering time in the progeny populations, during the period 1981∼1984.