Production of cytoplasmic male sterile rice (Oryza sativa L.) by cell fusion

In order to transfer cytoplasmic male sterility (CMS) of an indica rice, Chinsurah Boro II (CBII), to a major japónica variety, Nipponbare, iodoacetamide inactivated Nipponbare protoplasts were fused with X-irradiated CBII protoplasts by electrofusion. Among 16 fusion-derived plants having diploid chromosome number, one was completely male sterile and morphologically identical to Nipponbare. Its male sterility was stably transmitted to all the backcross progeny giving evidence for maternal inheritance of the trait. Furthermore, the CMS trait of backcross progeny was reverted to fertility in a gametophytic manner by Restorer of fertility gene (Rfl) derived from CBII. Restriction fragment and Southern blot analyses revealed the presence of CBII-derived mitochondrial plasmid DNA in the male sterile plant. Our study indicates that cell fusion can be used to transfer CMS to desired varieties of rice for future hybrid seed production.