Effect of Gamma Radiation on M1 Generation of Two Aromatic Rice Varieties and Determination of Their Lethal Dose

Gamma irradiation is a potent tool for inducing genetic variation in aromatic rice. This study evaluated the effects of gamma radiation on the M₁ generation of two aromatic rice varieties, Chinigura (local) and Banglamati (released), and determined their lethal dose (LD₅₀) based on plant survival. One hundred grams of seeds from each variety were irradiated at 0, 100, 200, 250, 300, and 400 Gy at the laboratory of the Bangladesh Institute of Nuclear Agriculture (BINA). The experiment followed a split-plot design with three replications and was conducted at the BINA Sub-station, Sunamganj, Bangladesh. Before irradiation, germination tests were performed under laboratory conditions (27 ± 2°C). Increasing radiation doses caused marked reductions in germination percentage, seedling height, fresh and dry biomass, tiller number, and survival. At 400 Gy, germination declined from 100% in the control to 87.0% in Chinigura and 81.3% in Banglamati. By 21 DAS, seedling height decreased by 16.7% and 19.4%, fresh weight by 51.0% and 45.6%, and dry matter by 48% in both varieties. Tiller number was reduced by nearly 50% at the highest dose. Survival declined linearly with increasing doses, and regression analysis estimated LD₅₀ values of 205.74 Gy for Chinigura and 325.92 Gy for Banglamati, indicating greater radiosensitivity in Chinigura and higher tolerance in Banglamati. These LD₅₀ values provide a key reference for mutation breeding and varietal improvement in aromatic rice.