Gamma irradiation studies on seeds, seedlings and callus tissue cultures of Phaseolus Vulgaris L.

Abstract

The effects of 60Co gamma radiation on seeds, seedlings and callus tissue cultures of Phaseolus vulgaris L. var. Manitou were compared. Tissues were subjected to various doses (0·5-40 kilorad) of gamma radiation at 200 rad/min and subsequently grown for 4-8 weeks. Seeds irradiated with 10-12 krad produced stunted seedlings which later exhibited delayed flowering, and poor seed set; although the seeds germinated, no normal seedlings were formed at 15 krad. However, when 8-day-old seedlings were irradiated, severe inhibition of growth occurred at 2 krad, followed by degeneration of the apical meristem and death at 5 krad. Callus grown in suspension cultures in a modified White's medium supplemented with 2, 4-D kinetin and yeast extract showed significant stimulation of growth (P< 0.01) at 0.5 krad followed by a gradual decrease from 1 to 10 krad. Cells in such cultures showed mitotic inhibition, degeneration of cytoplasm, increased polyploidy and reduced plating efficiency. Callus growth at 20-30 krad was drastically reduced and ceased completely at 40 krad. The color of the callus continued to darken with increasing doses. There is a striking difference in the radiosensitivity of seeds, seedlings and callus tissue; the young seedlings are most radiosensitive, followed by seeds, and callus tissue is most tolerant. © 1970 Pergamon Press.