Genetic Variability, Heritability and Selection of M2 Sorghum Super 2 Mutant Lines Derived from Irradiation Using Gamma Rays

Sweet sorghum (Sorghum bicolor L. Moench) is a potential plant to be developed as food, feed, and industrial raw materials. In Indonesia, sweet sorghum breeding is needed because only five varieties of sweet sorghum have been released. Genetic variability is essential in breeding. Through mutation induction, breeders can increase genetic variability so that new characters superior to their parents can be obtained. This study aimed to analyze the effect of various doses of gamma-ray irradiation on genetic variability in the agronomic character of the M2 population derived from the sweet sorghum Super 2 mutant and to select potential populations for further selection. The research was carried out at Experimental Garden, ICABIOGRAD, in February-June 2021. The material used was selected M2 mutant seeds from mutant populations resulting from gamma-ray irradiation of sorghum’s shoots of Super 2 variety with doses of 40, 50, 60, and 70 Gy. Variables observed were plant height, stem diameter, panicle length, panicle diameter, sugar content, and fresh and dry panicle weights. The results showed that all radiation doses could increase genetic variability in M2 plants compared to their parents. Significant differences in characters between the original parents and the M2 population with a dose of 40 Gy were seen in the top diameter of the stem, panicle length, and sugar content; at a dose of 50 Gy in panicle diameter, sugar content, and fresh panicle weight; at a dose of 60 Gy on plant height, top stem diameter, sugar content, fresh panicle weight; while at a dose of 70 Gy on bottom stem diameter and middle stem diameter. The potential population for further selection based on fresh weight is the irradiated mutant population with a dose of 70 Gy. In pre-analysis using Cluster Gram and 49 mutant genotypes of the 70Gy M2 population, a group of mutants similar to their parent (Super 2 sorghum variety) and the other group that was completely different from their parent was obtained.