Volume 70 (1995) Issue 4 Pages 555-562
Rice cultivars so far examined mostly had the early-heading gene, Ef-1. Their wild progenitor, Oryza rufipogon Griff., was examined in respect to the genes for heading time in the present study. Of three strains tested, W593 from Malaysia and W1623 from Tauyuan, Taiwan produced no panicles when planted in the first crop season at Taichung, suggesting their strong sensitivity to photoperiod, while W630 from Burma was practically insensitive to photoperiod and produced panicles. In the second crop season, the wild strains headed several days later than Taichung 65. When they were crossed with Taichung 65, the heading dates of the F1 plants were similar to, or a few days earlier than that of Taichung 65. In the B1F1 (T65 × F1) populations, early-heading plants like Ef-1 carriers were found. They were backcrossed to Taichung 65 several times and true-breeding early-heading lines were obtained. When they were crossed with T65(20)E a carrying Ef-1a, the heading dates of the F2 plants varied within the parental range, suggesting that the wild strains had similar alleles at the Ef-1 locus.
Regarding genes controlling photoperiod sensitivity W593 and W1623 were found to have recessive ones denominated as se-7 (t) and se-6 (t), respectively. The effect of these genes can be suppressed by Ef-1 when combined together.