Genetic Variability and Heritability Estimates in M1–M3 Generations of Kuantan Singingi Local Rice (White Sage Genotype) Induced by Gamma Radiation

Rice (Oryza sativa L.) is a critical staple crop in Indonesia, particularly in Kuantan Singingi Regency, where local rice varieties exhibit several advantageous traits but also possess notable limitations. This study aimed to induce genetic variability in a local rice genotype ("White Sage") through gamma ray irradiation, with the goal of selecting promising mutant lines based on their phenotypic and heritable traits. Gamma irradiation at a dose of 300 Gy, previously determined to be effective, was applied to M0 seeds, with untreated seeds (0 Gy) serving as controls. A total of 600 plants per treatment were cultivated in a randomized complete block design (RCBD) with five replications. The experiment was conducted under rainfed conditions in Pebaun Hulu Village, Kuantan Mudik District, from April 2024 to April 2025. M1 mutants were evaluated for key agronomic traits, and selected M2 lines were advanced using the bulk method. In the M3 generation, nine mutant lines were identified and characterized. Results indicated that most traits observed in M1 and M2 generations, including plant height, number of seedlings, number of productive tillers, flag leaf length, and grain characteristics, exhibited broad genetic variability and high heritability. In the M3 generation, plant height, number of seedlings, productive tillers, flag leaf length, and number of empty grains showed wide genotypic variability. However, the number of filled grains and weight of 100 grains showed narrow genetic variability. High heritability estimates in M3 were observed for the number of seedlings, productive tillers, and number of empty grains, while other traits demonstrated lower heritability. These findings suggest the potential for effective selection of superior mutant lines with improved agronomic performance in future breeding programs. Keywords: Gamma Ray Irradiation, Genetic Variability, Heritability, Local Rice, Mutagenesis, Oryza sativa.