Effects of genes T, D1, and D2, which regulate flower initiation, and maturity genes Ma1-Ma4 on the heading response in sorghum

The heading responses of six cultivars of sorghum having maturity genes Ma1-Ma4 were compared with those of seven cultivars having T, D1 and D2 genes, which regulate flower initiation. In addition, the relationship between these two genotype groups in the heading responses was analyzed by progeny tests. From the results, it was shown that the heading responses of six cultivars having Ma1-Ma4 genes could be explained by those of cultivar having T, D1 and D2. From the heading response of the cultivar 100M to the extremely low temperature on late June in 2002, it was suggested that 100M had the thermo-sensitivity gene T. The presence of gene T in 100M was confirmed by the heading response of the test cross F1 (MS 79.A x 100M). Furthermore, from the delay of 60M by exposure to minimum temperature over 20 deg C, the presence of the thermo-sensitivity gene T in 60M was suggested. The heading response of F1 (390A x 60M) could be explained by the presence of gene T in 60M.