[Genetic analysis of dominant earliness of rice genic male sterile line 6442S-7]

F1 progenies of a genic male sterile and early maturing indica line 6442S-7 crossed with sixteen medium or late maturing varieties, such as Minghui 63, shared the same heading date as 6442S-7 under long day and short day, suggesting that 6442S-7 has completely dominant earliness. Segregation of heading dates of the F2 and B1F1 populations indicated that the earliness of 6442S-7 is mainly controlled by two dominant major genes. Whereas, heading dates of F1 progenies of 6442S-7 crossed with other four late maturing varieties, i.e. IR68, Xianguo, 9311, and BG1639, closed to the mid-parent value under long day. In F2 populations of 6442S-7 crossed with each of the four late maturing varieties, F1 from three-way crosses between 6442S-7 and each F1 of Minghui 63 crossed with each of the four late maturing varieties, and F1 from three-way crosses between 6442S-7 and each F1 of crosses between each two of the four late maturing varieties, segregation of heading dates showed that an incompletely diminant allelic suppressor for the dominant earliness of 6442S-7 existed in the late maturing varieties, IR68, Xianguo, 9311, and BG1639. It is considered that dominant earliness genes harbored in 6442S-7 have splendid future in rice improvement.