Effect of acute gamma radiation exposure on seed germination, survivability and seedling growth in cumin cv. Gujarat Cumin-4

Abstract

Cumin production and productivity is very low because of lack in inherent capacity and susceptibility to wilt and blight. This crop has low genetic variability for different essential traits and improvement of this crop through conventional breeding approaches is very tedious. The induction of genetic variability through physical mutagen could be aviable approach to generate variability in cumin. An experiment was carried out to determine the LD 50 of gamma radiation in cumin for identifying most effective dose. In first experiment cumin seeds were irradiated with different gamma rays doses (100 Gy, 200 Gy, 300 Gy, 400 Gy and 500 Gy). At the lowest dose (100 Gy) of gamma ray maximum seed germination (90.47%) was obtained while the highest dose (500 Gy) resulted in minimum seed germination (9.52%). The dose of 300 Gy recoded 35.71% germination and 4.76% seedlings survival, respectively. In the latter growth stage none of the seedlings survived at the dose of 400 Gy and 500 Gy. At lower dose of 100 Gy maximum number of leaves (7), number of roots per plant (5.00), root length (4.27 cm), shoots length (2.9 cm) and fresh weight per plant (0.009 g) were observed. The seed germination, seedlings survivability and growth parameters were adegnate at 100 Gy and 200 Gy doses of gamma ray. To know the LD 50 more precisely another experiment was carried out on the basis of preliminary experiment. In this experiment 5 different doses were selected from 100 Gy to 200 Gy giving the interval of 25 Gy. The seed germination and seedlings survival decreased as the radiation dose increased. The maximum seed germination, was noticed at 100 Gy (95.5%) followed by 125 Gy, 150 Gy, 175 Gy, and 200 Gy. The seedlings growth parameters like number of leaves, root length, shoot length and fresh weight per plant reduced around 50% at 200 Gy dose of gamma radiation. Among the five doses of irradiation the LD 50 was close to 200 Gy which caused around 55% death of seedlings, 45% seedlings survival and around 50% reduction in plant growth. Hence, it is concluded that 200 Gy may be the optimum dose for creating useful mutation in cumin.