Effects of Gamma-ray Irradiation on Cultured Anthers of Tobacco(Nicotiana tabacum L.)-Radiosensitivity and Morphological Variants Appearing in the Haploid Plants.

Tobacco anthers which had been cultured for 0, 10 and 20 days were irradiated with 0 to 160Gy of gamma-ray. Anthers cultured for 10 days before irradiation, which were correspondence to a plantlet initiation stage of microspore, were most radiosensitive and RD50 for RACR (defined as dose resulting in 50% reduction in relative anther culture response) was 8Gy. On the other hand, RD50S for RACR in the anthers precultured for 0 and 20 days were 50Gy. The highest frequency of morphological variants was also obtained from the plants derived from irradiated anthers precultured for 10 days. These results suggest that gamma-ray irradiation on the anthers precultured for 10 days is most effective in inducing mutation in tobacco. Some of the variants were observed as sectorial chimera, but there was no clear relationship between the size of chimera and the developmental stage of the microspore at irradiation.