Integration of gamma irradiation breeding from doubled haploid and systematic screening to develop adapted rice mutants under salinity stress

Gamma radiation breeding is a significant approach for developing salt-adapted rice varieties that are crucial for food security, particularly in archipelagic nations such as Indonesia. The generated mutation diversity is inherently random and requires a large population. Optimizing mutations requires a systematic methodology that encompasses the induction potential and selection processes. This can be accomplished by optimizing mutations in double haploid lines and screening for salt tolerance within extensive mutant populations. This study aimed to optimize the mutagenic radiation dose in double haploid rice lines and develop a method for screening salt tolerance from germination to the seedling stage. The M1 generation underwent gamma ray irradiation at doses of 0, 200, 400, 600, 800, and 1000 Gy on the double haploid line HS4-15-1-63. The optimized M1 results were advanced to the M2 generation. This process was performed through salinity screening in three stages: germination under salt stress, seedling phase screening in saline soil, and evaluation of the growth and production of adaptive mutants. Research findings show that the optimal radiation dose for inducing diversity in Generation M1 ranged from 200 to 400 Gy, with 200 Gy yielding the highest diversity in Generations M1 and M2. A dose of 200 Gy enhanced the adaptability of HS4-15-1-63 to salt stress. The screening method that integrates the germination and seedling phases with saline soil in trays proved to be efficient. Therefore, a 200 Gy dose and this systematic selection concept are recommended for optimizing mutant adaptability from double haploid lines to salinity stress.