Rice mutants obtained by anther culture

Abstract

The anther culture technique was applied on three Japanese rice varieties, Koshihikari, Kagahikari and Notohikari, to obtain useful mutants for breeding. After cold pretreatment (5℃) for 7-10 days, anthers were inoculated on the callus-inducing media at the stage that the distances between auricles of the last two leaves were 5-10cm. For callus formation, two kinds of media were used : Ne basic medium supplemented with 2, 4-D 0.2mg/l, NAA 1mg/l and sucrose 70g/l (N_6-1 medium) and N_6 basic medium supplemented with 2, 4-D 2mg/l, yeast extract 1g/l and sucrose 70g/l(N_6-2 medium). For plantlet induction, the N_6 basic medium supplemented with NAA 0.5mg/l, kinetin 1mg/l and sucrose 50g/l was used. Chromosome number was counted by the Giemsa staining method in root-tip cells of A_1 plant (1st generation of regenerated plants). A_2 lines were cultured in paddy field separately as panicle-row lined from all panicles of A_1 plants. The frequency of callus formation was higher on N_6-2 medium than on N_6-1 medium, though they were very low (2.8% on average) (Table 1). The plantlet induction was higher from the pollen calluses formed on N_6-2 medium than those formed on N_6-1 medium (Table 2). A half number of regenerated plants were albinos. Chromosome counts of regenerated plants showed x (30.3%), 2x (64.8%), 3x (3.5%) and 4x (1.4%) (Table 3). In Koshihikari, the occurrence of mutation in A_1 plant level was estimated to be 32.2%. 1242 lines of A_2 generation as the panicle-row lines from 90 A_1 plants were cultured in paddy field. Among them, 81 mutant lines were discovered. Various mutants in connection with heading date, culm length, leaf shape, leaf color, ear shape or sterility were also found (Table 4). Useful mutants having characters of early maturity and/or short culm were obtained (Table 5). In Kagahikari and Notohikari, mutants with delayed maturity (7 days later than control) and non-white beliverering grains were obtained, respectively. The behaviour of occurrence of these mutations in A_1 plant was discussed. Above mentioned results show that the anther culture technique is an useful means of mutation breeding in rice.