Determination of Lethal Dose and Assessment of Growth Performance Following Gamma Irradiation for Mutation Induction in Rice

Determining the optimal radiation dose according to its impacts on crop growth characteristics is vital for effective mutation breeding. This study aimed to determine the lethal dose 50 (LD50) and assess the growth performance of gamma-irradiated rice mutants of the Nepali Swarna variety. Rice seeds were exposed to gamma irradiation using Cobalt-60 (⁶⁰Co) at eleven dose levels, ranging from 100 to 600 Grays (Gy) in increments of 50 Gy, along with a non-irradiated control (T0). Germination percentage was assessed after 7 days, while 14 days provided to evaluate shoot length, root length, fresh weight and dry weight of both the shoots and roots, and at 21 days the survival percentage was evaluated. The results showed that gamma irradiation significantly influenced all growth parameters compared to the control. The LD50, based on survival percentage, was determined to be 513 Gy. Growth parameter values exhibited a linear decline with increasing radiation doses, with the most pronounced effects observed at 600 Gy. The findings suggest that 513 Gy can be considered an effective dose for inducing genetic variability in Nepali Swarna, balancing mutation induction with minimal lethal effects for subsequent generations.