Comparative radiosensitivity of soybean genotypes to electron beam and gamma ray irradiation for optimisation of GR50 and LD50 doses

Mutation breeding provides a valuable tool for generating variability and enhancing agronomic traits in crop plants that are vital for food security. However, it demands precise implementation and thorough screening to promote higher mutation frequencies without excessive lethality. The present study was carried out to compare two sources of radiations, viz., electron beams and gamma rays and to estimate optimum doses of GR 50 and LD 50 in four soybean genotypes. The study showed dose dependent negative correlation with radiation doses for both type of radiations. Germination was the least sensitive to radiation, exhibiting minor or cultivar-specific effects, making it a relatively stable trait under radiation stress compared to other seedling traits. Epicotyl length and survival percentage were the most sensitive traits to irradiation doses with drastic reductions in epicotyl length and complete seedling mortality occurring at higher doses (600–700 Gy). For electron beams, the GR 50 dose based on reduction in epicotyl length ranged from 338.8 to 360.2 Gy; while the LD 50 dose varied from 332.7 to 352.5 Gy across the genotypes. Similarly, gamma rays also showed GR 50 dose ranging from 284.3 to 318.2 Gy and LD 50 dose from 310.4 and 337.0 Gy among soybean genotypes. These dose differences among genotypes can be attributed to genotype-specific radiosensitivity. The study demonstrated comparable effects on various seedling traits between electron beam and gamma ray treatments at equivalent doses, indicating that electron beam could serve as a potential alternative radiation source in soybean mutation breeding programs.