COOL TEMPERATURE-SENSITIVE MUTANTS AT THE BOOTING STAGE OF RICE

The genetic mechanism of cool temperature resistance at the booting st age of rice, is largely unknown in spite of the significance in rice c ultivation. We have screened 317 M2 lines derived from chemically muta genized cv. Taichung 65 which is highly resistant to cool temperature. Repeated screening from M3 through M6 generation recovered seven cool temperature sensitive mutants. They showed significantly lower seed f ertility than Taichung 65 when treated with cool water (19-degrees-C). Although the seed fertility fluctuated to some extent with years, fou r of the seven mutants showed very low seed fertility and one relative ly high but significantly lower seed fertility than Taichung 65. The r emaining two showed intermediate values. Segregation of seed fertility in F2 plants between Taichung 65 and the mutants suggested that many of the mutants were due to single-gene recessive mutations. In four mu tants, pollen development was severely damaged by cool water treatment . Also female organ (embryosac) was malformed in some mutants. These s even mutants are potential materials for the investigation of cool res istance in rice.