A gametocidal factor of Oryza glaberrima Steud. in O. sativa L.

Summary Recurrent backcrossing has been carried out with a view to transfer a gene for non-glutinous endosperm from two strains of O. glaberrima (Wx_g/Wx_g) to glutinous japonica and indica varieties (wx/wx) of Oryza sativa. In the course of backcrosses Wx_g/wx segregants were crossed with each of the two glutinous varieties of sativa as the respective recurrent male parent. The wx/wx and Wx_g/wx segregants in the successive generations were consistently fully fertile and semi-sterile, respectively. The semi-sterility of Wx_g/wx plants was attributable to abortion of most of the pollen grains carrying the gene wx. The nucleus but not cytoplasm was related to the semi-sterility. The Wx_g/Wx plants having the gene for non-glutinous endosperm of a glaberrima strain and a japonica variety of sativa were also semi-sterile. Both wx- and Wx-megaspores in the plants heterozygous for the gene Wx_gwere deleteriously affected. The results could be explained by assuming that a factor tightly linked with the gene Wx_gof glaberrima sterilizes gametes not carrying it in the heterozygotes and that the gametocidal action is exerted when combined with the sativa nucleus by the recurrent backcross method.