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¬ypes. 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.
