Vol. 12, Issue 9 (2023)

Author(s):
SR Merrin Rabinya, C Babu, T Ezhilarasi, V Manivannan and V Ravichandran

Abstract:
Seeds of fodder cowpea varieties CO 8 and CO 9 were irradiated with different doses of Gamma rays from 100 Gy to 2000 Gy for the purpose of creating variability and broaden the genetic basis. The treated seeds were raised in seedling trays where the survival rate was nearly zero at the doses from 1600 - 2000 Gy. Lethal Dose 50 (LD₅₀) values were determined using probit analysis based on the germination (or) mortality percent as 658.52 Gy for CO 8 and 626.82 Gy for CO 9 and effective doses were fixed viz., 559 Gy, 659 Gy and 759 Gy for CO 8 and 527 Gy, 627 Gy and 727 Gy for CO 9. Study on M₁ generation was carried out and parameters like germination percentage at seventh day after sowing, seedling shoot length, seedling root length, seedling vigor index, survival rate on 30^th day after sowing, pollen fertility and quantitative traits like plant height at 30^th day after sowing, leaf length, leaf breadth and number of primary branches at fodder harvesting stage were recorded. These seedling parameters and quantitative traits exhibited a decreasing trend along with the increasing doses of gamma rays which resulted in considerable variability. In M₂ generation, the presence of chlorophyll mutants was observed and these mutants include Albina, Chlorina, Xantha, Viridis, Xantha viridis and Aurea which occurred in different relative frequencies in the corresponding two fodder cowpea varieties. The chlorophyll mutation Aurea occurred at a very low frequency in both the varieties CO 8 and CO 9. These decreasing trends in seedling parameters and quantitative traits and the occurrence of chlorophyll mutants represent the potency and efficiency of the mutagen. It was observed that the seeds of variety CO 9 were more sensitive to gamma rays than CO 8.