Improving the grain quality of anna r 4 rice cultivar through physical and chemical mutagens

Abstract

The present experiment was carried out with the aim of improving the grain quality traits of the popular rice variety Anna (R) 4, which is having long slender grains with drought tolerance nature. Due to the presence of long slender grain type, recovery of head rice is low, which is reflected in the low marketable prices. Hence, an attempt was made to irradiate the Anna (R) 4 rice through physical and chemical mutages for the isolation of desirable mutant with acceptable grain quality traits. This study also investigated the effectiveness and efficiency of emerging physical mutagen viz., electron beam over conventionally used gamma rays and probe the drought tolerance, cooking and nutritional qualities of some mutant families from advanced generation (M6), evolved through EMS treatment. According to the germination and lethality, LD50 values were fixed as 376.57 Gy for gamma rays and 273.27 Gy for electron beam. The traits like germination percentage, root length, shoot length, pollen and spikelet fertility was more affected in both the irradiation approaches with increasing the dosage. On the basis of in vitro study on growth (GR50) and fertility reduction, root length was more affected than the plant height and days to maturity. Among the physical mutagens, electron beam caused maximum reduction compared to gamma rays. The viable mutant frequency was higher in 300 Gy of electron beam than all other treatments and mutagen. However, efficiency was comparatively higher in gamma rays based on lethality and injury. The effectiveness and mutation rate was prominent and maximum number of useful mutants was found in electron newlinebeam treatment. In M2 generation, six different types of chlorophyll mutants such as albino, chlorina, xantha, stirata, tigrina and albomaculata were identified and among them albino showed maximum frequency in electron beam. Regarding morphomutants, early flowering, high tillering and grain type mutants displayed in higher frequencies by electron beam; whereas, awn type mutants were o