CYTOPLASMIC-GENETIC MALE STERILITY IN CULTIVATED RICE, ORYZA SATIVA L.

A case of cytoplasmic male sterility controlled by a restoration gene Rf was found in cultivated rice, Oryza sativa L. The sterile cytoplasm [ms] and the restoration gene Rf were derived from Chinsurah Boro II, an Indica variety, and the experiments were made by the isogenic lines having genetic background of Taichung 65, a Japonica variety.When a plant with sterile cytoplasm [ms] had Rf Rf, it was completely male-fertile; when it had Rf rf, partially male-fertile (ca. 50%); and when it had rf rf, completely male-sterile. Plants with normal cytoplasm [ms+] would be male-fertile regardless of the genotype for restoration genes. The F1 plants of [ms] rf rf×[ms+] Rf rf segregated into partially male-sterile and completely male-sterile classes in a 1:1 ratio, while the selfed progeny of [ms+] Rf rf was completely male-fertile. The restoration gene was thus found to be of gametophytic type.The F1 plants of [ms] rf rf×Rf Rf had a 90% or higher seed set, though they were partially male-sterile. This source may be used for breeding "hybrid rice".