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RADIOSENSITIVITY STUDIES IN BASMATI RICE

AKBAR ALI CHEEMA AND BABAR MANZOOR ATTA

Abstract: Three Basmati rice varieties (Basmati 370, Basmati Pak, and Super Basmati) were used to examine varietal differences in radiosensitivity to gamma radiation. Dry seeds of rice varieties were exposed to 150, 200, 250 and 300 Gy of gamma rays. Sensitivity to dose was determined by various measurements on the M₁ generation and on the basis of frequency of various types of chlorophyll mutations obtained in the M₂ generation. With the increase in radiation dose a decrease in germination, seedling height, root length and emergence under field conditions was observed in M₁ generation. In contrast, the gamma rays doses had some stimulatory effects on total spikelets at the maturity stage. These effects were observed in all the gamma radiation treatments in case of Basmati 370 where total spikelets increased above the non-irradiated control. Plant height and seed fertility decreased with increase in gamma radiation dose in an approximately linear fashion. The LD₅₀ values for seed fertility were 238, 232 and 223 Gy for Basmati 370, Basmati Pak and Super Basmati, respectively. The effectiveness of the dose in inducing genetical changes was estimated by counting the number of chlorophyll mutations in the M₂ generation. The frequency of chlorophyll mutations increased with the radiation dosage upto 250 Gy which sharply decreased thereafter. Gamma ray dose of 200 and 250 Gy produced the highest mutation frequency for Basmati 370 followed by Basmati Pak and Super Basmati. The albina type of mutation was most frequent in all the three varieties.
 

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