MUTAGENIC STUDIES IN RICE
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Date
1985
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Birsa Agricultural University
Abstract
Radio genetical studies in rice (Oryza sativa L.) received a fairly wide importance since 1934 as is evident from the pioneering studies of Ramiah and his associates in India and those of Ichijima in Japan. The increased application of physical mutagens attained prominence in the 'Atom Era' of the forties and fifties which contributed to the isolation of a large number of mutants in various crops including rice.
In the present study, dry and dormant seeds of six rice varieties, viz. Archana, BR8, Ch1039, Ratna, IR36 and Sita were treated with different doses of gamma rays like 12 Kr, 24 Kr, 36 Kr and 48 Kr and studies were made in M, and M₂ generations with the ultimate object of creating variability and to find out whether varietal differences exist for mutability and radio sensitivity in such varieties.
In the generation, germination of seeds were found to be reduced in treated lines and a linear negative correlation between radiation doses and germination percentage were also observed. The variety BRB was found to be the most radiosensitive whereas Archana the least. The shoot and root length was drastically reduced in higher doses in all the varieties under experiment. Ratna was the most affected variety in respect of shoot length while Archana and BR8 in root length. The shoot:root ratio increased with increasing doses in all the varieties excepting Ch1039 and Ratna where the increase was upto 36 Kr and thereafter it decreased. In general it was found that gamma rays have more influence on root than on the shoot. A linear negative correlation was observed with radiation dose and seedling survival. Ratna showed the most drastic effect with only 26 percent seedling survival at 48 Kr while Ch1039 and IR36 showed the least the (60 percent) survival. Seedling height at 25 day after treatment was also found to be reduced in all the varieties while Ratna affected most drastically and Ch1039 the least. The filled grain percentage per panicle and the dose was found to have a linear relationship with a negative correlation in all the varieties. Ratna and Archana were the most sensitive and resistant varieties, respectively. The plant survival percentage at maturity decreased with increase in radiation doses in all the varieties. Among the varieties Ratna was found to be the most radiosensitive and BR2 the least.
In the 1₂ generation chlorophyll mutation frequency increased with increase in radiation doses. The mutation frequency were higher then determined in terms of H₁ plant basis than in M, panicle basis. Thechlorophyll mutants isolated were: (1) Albina, (11) Xantha, (111) Virina-xanthescens, (iv) Xantha-virescens, (v) Alboviridis, (vi) Striata and (vii) Tigrina. Albinaoccured most frequently and Tigrina most rarely. Variation in quantitative characters like days to 50% flowering,number of effective tillers, panicle length, plant height, grain shape and size and 100 grain weight were also obtained with both increase and decrease in the mean value and co-efficient of variation in all the varieties. Quite a large number of morphological mutants like bend node mutant, extended glumes, multi-leafy branches, grassy mutants, twisted flag leaf were also isolated.
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MUTAGENIC STUDIES IN RICE