Optimum gamma irradiation doses for mutagenesis in Bambara groundnut (Vigna subterranean L.) genotypes

Abstract

Genetic diversity enhancement to select Bambara groundnut (Vigna subterranea [L.] Verdc. 2x = 2n = 22) breeding lines with economic traits is imperative to improve the crop's utilization in Sub-Saharan Africa. Gamma radiation is a vital mutagenic agent to create novel allelic combinations required for developing climate-smart Bambara groundnut varieties to contribute to food production and nutrition security in drier regions, including Namibia. Therefore, the objective of the present study was to identify optimal gamma radiation doses to enhance genetic diversity in Bambara groundnut genotypes. The present study was conducted in root boxes under a custom-made shade-net house at Mannheim Crop Research Station, Tsumeb, Namibia. Three Bambara groundnut genotypes (Uniswa Red, Dip C and KFBN 9709) were gamma irradiated at six doses (0, 50, 100, 150, 200, and 250 Gy) were laid out in a randomized complete block design (RCBD) with three replications. Data were collected on days to emergence (DTE), emergence percentage (%EM), seedling survival percentage (%SS), seedling length (SLT), and shoot weight (STW). A non-significant interaction of genotype × gamma radiation dose was detected, showing stable responses indicating that genotypes require varying gamma radiation doses for mutagenesis. A significant (p < 0.01) genotype effect was found on days to emergence, emergence percentage, seedling length and shoot weight, indicating that gamma radiation doses requirements for individual genotypes varied. Significant (p < 0.05) effects of gamma radiation doses revealed that the traits could be used to select optimum doses to be upscale in induced mutation breeding programs of Bambara groundnut. Seedling length was the only trait with higher growth reduction that resulted in a negative trends. A linear regression model predicted LD₅₀s for Uniswa Red, Dip C and KBFN 9709 at 428.1, 523.7 and 712.5 GY, respectively. These doses were higher than test gamma radiation doses, indicating the need for higher doses resulting in LD₅₀s. Therefore, the doses identified in these studies are useful for use in induced mutation breeding for the tested Bambara groundnut genotypes.