Viable mutations inducted by gamma rays in groundnut

Abstract

The effects of gamma radiation at three doses (20, 30 and 40 krad) were studied in three selected genotypes of groundnut viz., Spanish Improved, TG 14 and TMV 2 with the prime objective of evolving early mutants. Observations on seed germination, seedling survival, plant height, pollen fertility and other effects ware made. Chlorophyll mutation frequency, mutant spectrum, rnutagenic effectiveness and efficiency were worked out. Germination of seeds was reduced by gamma rays and a progressive decline in germination with increasing doses was noticed. The survival was also reduced in all the genotypes and the relationship between the percentage of survival and doses of radiations was inverse. A reduction in plant height was noticed in tha three genotypes on the 30th day. Pollen fertility deceased with increasing doses. The frequency of chlorophyll mutations increased with increasing doses of gamma rays in all the genotypes; the maximum baing for TG 14. Albina; xantha, chlorina and viridis were the chlorophyll mutants observed, of which viridis was seen the most frequent. No definite relationship was seen in any of the genotypes between doses of radiation and mutagenic effectiveness. In TMV 2 and Spanish Improved, effectiveness was the maximum at the highest dose of radiation tried (40 krad) while in TG 14, it was at tha intermediate dose (30 krad). Mutagenic efficiency, too, did not show ony specific relationship with the radiation doses in the g&notypes. TMV 2 and TG 14 at 20 krad and Spanish Improved at 40 krad recorded the maximum mutagenic efficiency based on lethality. Based on injury and sterility, the highest efficiency was noted at 40 krad and 20 krad in TMV 2 and Spanish Improved respectively and both at 30 krad in TG 14. A wide range of viable mutants was isolated in the M3 generation affecting almost all the characters including early mutants of great practical utility. Macromutants with simultaneous change in a constellation of characters were isolated.