Restorable variation of cytoplasmic type of male sterile line in rice by in vitro culture

Rice male sterile (MS) lines, IR66707A and IR69700A, which possess the cyto plasm of Oryza perennis and O. glumaepatula respectively, belong to the cyt oplasmic type. Their sterility could be maintained but not be restored. By somatic cell culture of these two MS lines, 47 somaclones with 465 R-1 plan ts were obtained. All of the 465 R-1 plants were sterile in the spring seas on in Guangzhou. According to the expression of the R-1 plants and the leve l of similarity to their donor parents, they could be divided into three ty pes, The plants of type I were male sterile, The sterility of some somaclon es of this type could be restored by the test crossing varieties or alterna ted to fertile by changes of some environmental conditions. The hybrid F-1 of test cross from the MS somaclones in type I was fertile while the hybrid F-1 from the donor MS lines was still sterile. The R-1 plants of type II w ere similar to the donor parents and also male sterile. The hybrid F-1 from all of the plants of type II crossed to test variety were still sterile, s o they did not possess restorability. For the somaclone of type III, all of R-1 plants were sterile in both male and female organs. No seed was set in both conditions of self and cross pollination. The fact that the restorabl e variants obtained in the cytoplasmic type of MS lines of rice by in vitro culture reported here should be the first sample in somaclonal variation i n plant kingdom.