Heat stress is an increasingly critical threat to rice production, especially during the highly sensitive reproductive stage. This study aimed to identify heat-tolerant rice mutants derived from the variety Binadhan-17 using gamma irradiation through phenotypic and SSR marker screening. Thirty-six M4 mutants and a heat-susceptible check (BRRI dhan28) were screened under controlled polytunnel conditions at the flowering stage, with daytime temperatures ranging from 35 to 45 °C. Phenotypic traits, including pollen viability, plant height, effective tillers, panicle length, filled and unfilled grains, spikelet fertility, seed weight, and grain yield plant− 1, were measured. Results revealed significant variability among genotypes under heat stress, mutants M5, M11, and M26 exhibited minimal reductions in both filled grains and spikelet fertility, indicating heat tolerance, whereas M9, M30, and M33 were highly susceptible. Pollen viability ranged from 40 to 90%, with heat-tolerant genotypes maintaining higher viability. Microsatellite marker analysis using 10 SSRs identified 53 alleles, with RM219, RM314, and RM242 being highly informative (PIC > 0.50). Cluster analysis grouped the mutants into four distinct clusters, while population structure analysis revealed admixture patterns reflecting mutation-induced genetic variation. The study demonstrates the potential of mutation breeding and marker-assisted selection for developing heat-tolerant rice varieties. Three mutants (M5, M11, M26) demonstrated high spikelet fertility and yield under stress, providing valuable genetic resources to sustain rice productivity under heat stress.
Barik et al. (Thu,) studied this question.