Gamma Irradiation Effects on Germination, Survival and LD50 in China Aster (Callistephus chinensis L. Nees)

Abstract

Gamma irradiation is an established approach for inducing genetic variability in mutation breeding, but appropriate dose selection is essential to avoid excessive seedling injury. This study evaluated the effects of gamma irradiation on seed germination, seedling survival and LD₅₀ estimation in China aster (Callistephus chinensis (L.) Nees). Seeds of six genotypes, namely Phule Ganesh Pink, Phule Ganesh White, Phule Ganesh Violet, Phule Ganesh Purple, Arka Advika and Arka Kamini, were treated with 0, 20, 40, 60, 80 and 100 Gy gamma rays using a ⁶⁰Co source. The experiment was laid out in a factorial randomised block design with three replications. Germination percentage, seedling survival percentage and genotype-specific LD₅₀ values were assessed, with LD₅₀ estimated through Finney’s probit analysis. Germination and survival declined progressively as the irradiation dose increased. Mean germination decreased from 97.50% in the control to 66.67% at 100 Gy, while mean seedling survival declined from 95.22% to 45.33%. Phule Ganesh Pink recorded the highest mean germination (82.50%) but the lowest LD₅₀ value (77.43 Gy), indicating greater sensitivity. Arka Kamini recorded the highest seedling survival (67.11%) and LD₅₀ value (134.55 Gy), suggesting comparatively higher tolerance. The findings indicate clear genotypic variation in radiosensitivity and support genotype-specific dose selection for further mutation breeding in China aster.