Heading Performance of Rice Varieties under Double Cropping on Ishigaki Island

摘要

In order to advance generations of hybrid populations of rice effectively, the heading performance of several varieties in the first and second cropping seasons on Ishigaki island was investigated, and heading dates of the varieties in both Ishigaki and in mainland Japan (Tsukuba city, Ibaraki prefecture) were compared. Number of days to heading in the second cropping season was less than in the first season for all the varieties used. The Japonica group showed a larger variation in heading performance than the Indica group, except for the strongly photoperiod-sensitive varieties, in the first and second seasons. The temperate type Japonica varieties headed earlier than the varieties of the Indica group and the tropical type Japonica. Most varietiesof the Indica group and the tropical type Japonica were late maturing in Ishigaki and Tsukuba. Number of days to heading of many Japonica varieties in Ishigaki became less than in Tsukuba except for the tropical type.