Genetic Studies on Photo and Thermo Sensitive Genic Male Sterility of Indica Rice

The inheritance of photo and thermo sensitive genic male sterility (PTGMS) in rice was studied on the basis of the bagged seed setting rate of segregating populations from the crosses of five indica PTGMS lines and three conventional indica varieties of different ecotypes under long daylength conditions by the Maximum Likelihood method. The results showed that: a) The sterility of Annong S 1, Ce-64S, Hengnong S 1 and W6154S was controlled by one pair of recessive major genes, while that of W7415S was controlled by more than one pair of recessive major genes; b) The expression of sterile major genes was modified by minor genes and the effect of minor genes was varied with PTGMS lines; c)The conventional indica varieties of different ecotypes possessed both the corresponding dominant major gene(s) and the genetic background affecting the expression of male sterility. The genetic background, in fact, was a group of minor genes and there existed a great difference among varieties. Furthermore, the mechanism of drift in critical sterility inducing temperature (CSIT) of PTGMS lines and the breeding strategy of viable PTGMS lines with a slight drift in CSIT were discussed in the paper.