GENETIC DIAGNOSIS OF CYTOPLASMIC MALE-STERILE CYBRID PLANTS OF RICE

Twelve Japanese rice cultivars were converted to CMS by asymmetric pro toplast fusion with MTC-5A, the cytoplasm of which was derived from an indica rice, Chinsurah Bore II. With the exception of the cybrids tha t had a nucleus from Hoshiyutaka, most of these cybrid plants were ste rile. The unique sequence downstream from the mitochondrial atp6 of MT C-SA was specifically amplified in the sterile cybrid plants by PCR. A ll progenies of the cybrid plants carrying this unique sequence were s terile. On the other hand, in some of the sterile cybrid plants in whi ch the unique sequence was not amplified by PCR, fertility was recover ed in their progenies. Somaclonal mutation may have caused sterility i n these cybrids. Only the cybrid plants that had the unique sequence d etected by PCR were CMS. Thus, the CMS plants can be selected rapidly and easily by PCR, at an early stage of plant regeneration. Soon after transplanting the regenerated plants to a green house, fertile cybrid s and sterile cybrids produced by somaclonal mutation can be removed. These findings also show that the unique region downstream from atp6 i s tightly linked with the CMS phenotype.