Radio-sensitivity of selected namibian landrace groundnut (Arachis hypogaea L.) genotypes to gamma radiation

Groundnut (Arachis hypogaea L.) is a popular nutritious food crop in the world. In Namibia, groundnut varieties are limited and characterized by low yields of 0.4 t/ha. Its production is challenged by biotic and abiotic stresses and low genetic variability in the agroecological zones of Namibia. Gamma-irradiation mutagenesis is a technique applied to generate genetic variation based on the genotype's sensitivity to the mutagenic agent for the selection of traits of economic importance that fulfill the user's requirements. This study aimed to determine the optimal lethal doses (LD₅₀) of mutagens producing maximum mutations with minimum damage for mass gamma-irradiation on Namibian landraces of groundnut in preparation for mutation breeding programs. Seeds of three groundnut varieties ('NAM 4433', 'NAM 888/2', 'NAM 1747/1') were subjected to six gamma radiation doses [0, 50, 75, 100, 125, and 150 Gy (Gy)]. The radiation source was Cobalt-60, with an irradiation rate of 28.81 Gy/min. Irradiated and non-irradiated (control) seeds were sown in plastic pots, using a factorial experiment with a randomized complete block design. Data were collected on parameters relating to seed germination, seedling growth, and plant survival of the varieties. A linear regression model was developed to determine the mean lethal dose (LD₅₀) and reduction dose (RD₅₀) of the varieties. Combined analysis of variance showed significant responses (p < 0.001) to seedling emergence, shoot, and root traits. Genotype NAM 4433 was most sensitive to gamma radiation doses ranging from 106 to 150 Gy. The doses could be used in mutation breeding programs to select mutants with desirable agronomic and nutritional traits for farmers and consumers. Genotypes NAM 1747/1 and NAM 888/2 did not respond to the doses applied. Further research using high radiation doses for NAM 1747/1 and NAM 888/2 is recommended.