Genetic analysis of regeneration ability in rice [Oryza sativa] seed-callus

The inheritance of in vitro shoot regeneration ability in rice seed-callus was studied with the cross combinations between a high and a low regeneration ability cultivar. The mature rice seeds were cultured on 1/2 concentration of MS basal medium containing 3 mg/1 2,4-dichlorophenoxyacetic acid (2,4-D), 5 g/1 yeast extract, 30 g/1 sucrose and ll g/1 agar for callus formation. The formed calli were transferred onto a medium composed of 1/4 concentration of MS plus 1/4 concentration of N6, supplemented with 2.5 mg/l 1-naphthaleneacetic acid (NAA), 8 mg/1 kinetin, 30 g/1 sucrose and 3 g/1 gelrite for regeneration. The high regeneration ability cultivars Aikoku and Sen-ichi with regeneration rate of more than 85%, and the low regeneration ability cultivar Moritawase with regeneration rate of no more than 2% were used as cross parents. In F1 progenies, the regeneration ability appeared similar to their high regeneration ability parents, and there was no difference between reciprocal crosses. F2 and BC1 populations showed two distinct patterns of regeneration ability, the high and low regeneration ability plants fitted the 3:1 and 1:1 ratio respectively. The results indicate that the difference of regeneration ability between the high and low parents in this study is controlled by a single dominant gene. The F2 population of Aikoku × Sen-ichi did not show segregation, suggesting that the dominant gene in these two cutivars is the same allele.