Effect of 60Co Gamma-ray Irradiation at Different Culture Stages on Rice Anther Culture.

Abstract

Gamma-ray irradiation was applied at different stages of rice anther culture. In rice anther culture we could divide three stages, namely (1) anthers prior to plating (ante-culture stage), (2) anthers plated on callus induction medium (dedifferentiation stage) and (3) induced calli plated on regeneration medium (regeneration stage). Irradiation at the ante-culture stage decreased the rate of callus formation and regeneration of green plantlets. During the dedifferentiation stage, irradiation also decreased the rate of callus formation, but did not affect the regeneration of green plantlets. Irradiation during the regeneration stage reduced the regeneration of green plantlets. In this study, we defined the number of anthers which regenerated green plantlets per number of plated anthers as plating anther efficiency (PAE). We used the PAE value as an index of radiation sensitivity of cell in vitro in anther culture because the PAE value is related to the callus formation rate and regeneration rate, and reflects the efficiency to obtain regenerated plants. Based on the PAE values, radiation sensitivity was the highest at the ante-culture stage, followed by the regeneration stage, and the lowest during the dedifferentiation stage. The RD50 values for PAE were about 6 Gy, more than 50 Gy and 20-25 Gy at the ante-culture, dedifferentiation and regeneration stages, respectively.