Effect of gamma rays on different parameters under laboratory and field conditions in M₁ generation in horsegram

Effect of different doses of gamma rays (5, 10, 15, 20, 25, 30, 35 and 40 kR on three varieties of horsegram viz., AK21, AK42 and Maru K1 under laboratory and field conditions (Macrotyloma uniflorum Lam. Verdc) was studied during summer, 2004. M₁ generation was raised both in flat and field condition. In flat studies, the relative biological damage in terms of reduction in germination, survival, root-shoot length and dry-fresh weight was reduced with increased gamma rays doses. Varieties, AK 21 and MK 1 for germination, MK1 for survival, shoot and root length and AK 21 for fresh and dry weight were found to be most resistant. In field studies in M₁ generation, the germination percentage decreased with increasing gamma rays doses in all three varieties of horsegram. Varieties, AK 42 and MK 1 were found to be the most resistant, while AK 21 was considered to be susceptible based on LD₅₀ value. Higher doses increased chlorophyll deficient chimeras and morphological abnormalities. Among the three varieties critically screened in M₁ generation, MK 1 was found most sensitive genotype while AK 42 and AK 21 was considered least sensitive genotypes to gamma rays irradiation. All the varieties exhibited greater mean value for all the characters under study, indicating survival of negative gene.