Radiosensitivity and Agronomic Responses of Bengkulu Rice Inbred Lines to Gamma-Ray Irradiation and Preliminary Selection of M₁ Plants

Gamma irradiation is widely used in mutation breeding to generate phenotypic variation for crop improvement. However, information on radiosensitivity and agronomic responses of Bengkulu-derived rice inbred lines remains limited. This study aimed to determine the lethal dose 50 (LD₅₀), evaluate agronomic responses to gamma irradiation, and identify M₁ plants for further evaluation. Four rice inbred lines (F8) from Bengkulu, Indonesia (267, 268, 269, and 270) were irradiated with gamma rays at 0, 100, 200, 300, and 400 Gy. LD₅₀ values were estimated using probit analysis based on seedling mortality, while agronomic traits were evaluated under field conditions using an augmented design. The evaluated M₁ population exhibited chlorophyll-deficient phenotypes, including albina, striata, and marginata, and variation in several agronomic traits. Estimated LD₅₀ values ranged from 201.96 to 221.78 Gy. Irradiation affected plant height, flag leaf length, panicle length, yield components, and grain weight per hill, with higher doses generally associated with reduced growth and productivity. Plants exposed to approximately 200 Gy exhibited phenotypic variation while maintaining relatively favorable agronomic performance. Weighted selection index analysis identified six M₁ plants with favorable combinations of reduced plant height, yield-related traits, and relatively earlier maturity. These plants warrant further evaluation in M₂ and subsequent generations to confirm the stability and heritability of the observed traits.