Induced variability and assessment of mutagenic effectiveness and efficiency in sorghum genotypes [Sorghum bicolor (L.) Moench]

Purpose Sorghum is an important cereal crop, cultivated for food, fodder and biofuel. Mutation breeding techniques are used to create genetic variability for qualitative and quantitative traits in crop plants. The purpose of this study was to create induced variability and estimate mutagenic effectiveness and efficiency of physical and chemical mutagens in two sorghum cultivars. Materials and methods Gamma rays (100, 200, 300 and 400 Gy, Co-60 source, Bhabha Atomic Research Center, Mumbai, India), ethyl methane sulfonate (0.1%, 0.2%, 0.3%, and 0.4% EMS, Sigma-Aldrich, Bangalore, India) and their combinations were used to mutagenize 296B (rainy season) and Parbhani moti (post-rainy) cultivars. Morphological and yield traits were analyzed for enhanced variability in qualitative and quantitative traits across M-2 and M-3 generations. Results Based on the mutagenic sensitivity, lethal dose at 50% survivability (LD50) for both the genotypes was found to be 269-281 Gy in case of gamma rays and 0.32-0.33% for EMS. Based on reduced germination and survivability, mutagenic sensitivity was dose dependent and genotype independent. High frequency of chlorophyll mutations (albino, xantha, viridis, variegated and chlorina) was linearly correlated with dose in both the genotypes. Among the favorable mutants, dwarf and brown midrib were isolated from Parbhani moti population, which could be used in the cross breeding programs. A combined treatment, 100 Gy + 0.1% EMS showed high mutagenic effectiveness and efficiency. Enhanced genetic variation for quantitative traits as measured by wide range values and coefficient of variation was attributed to the effect of physical and chemical mutagens. Early flowering and high grain yield (24-49% increase over control) mutants were identified in M-2 and validated in M-3 generation in both genotypes. Conclusions This study has revealed wide genetic variability and better effectiveness and efficiency of the physical (300 Gy) and chemical mutagens (0.2%) and their combination (200 Gy + 0.2%) across two sorghum genotypes. Significant correlations identified between quantitative traits will help in better selection in the segregating generations.