Effects of acute gamma irradiation, developmental stages and cultivar differences on growth and yield of wheat and sorghum plants

Three cultivars of Triticum aestivum (Yecora, Chenab-70, and Pari) and of Sorghum vulgare (Pq. 7. dwarf, Ks. 12. medium dwarf, and Ts. 100. tall) were exposed to acute gamma rays (60Co) at three developmental stages, i.e. 1-leaf, ear emergence, and anthesis. Exposures ranged from 0.5-7 krad for wheat and 1-10 krad for sorghum. In wheat plants exposures of 0.5 and 1.25 krad had in general a stimulatory effect on height, tillering, ear number and grain yield per plant at the 1-leaf stage, but an adverse effect on the above characters at the ear emergence and anthesis stages of development. Among the three cultivars, Yecora and Pari were the most radiosensitive (LD100-2.5 krad) and Chenab-70 the most radioresistant (LD100 -5 krad). The three cultivars also differed in their ontogenetic sensitivity. In sorghum, cultivar Ts. 100. tall showed a large reduction in mean seedling height, tillering and ear number per plant at all exposures at the three stages of irradiation. A large reduction in seed set was found in Pq. 7. dwarf and Ks. 12. medium dwarf. Cultivar Pq. 7. dwarf was found to be the most radiosensitive for yield reduction (YD). (author)