Biochemical changes and gene expression in mutant ‘Tai Nguyen’ rice variety in response to gamma irradiation and salt stress

Rice (Oryza sativa L.) is a vital staple crop globally, but its susceptibility to salt stress poses significant challenges to productivity, particularly in regions like the Mekong Delta, Vietnam. Saline intrusion in this area induces osmotic stress, hampers germination, and alters root morphology. In this study, we focus on the potential role of gamma irradiation in mitigating salt stress in rice. Mutant ‘Tai Nguyen’ seeds with different gamma doses (0-control, 50, 100, 150, 200, 250 and 300 Gray) were put under various NaCl concentrations (0 - control; 1‰; 2‰; 3‰; and 4‰). The results showed that the average germination time was approximately 1.7 days, with slight delay under 4‰ NaCl (2.7 days). A decrease of growth parameters under 300 Gy, 4‰ NaCl was 11.1% for the average germination percentage and 52.1 mm for plant height, compared to 0 Gy, 0‰ NaCl. The highest chlorophyll content (2.10 mg g-1 f.wt) was recorded at 100 Gy under non-saline conditions, while higher radiation doses resulted in a gradual decline in chlorophyll levels. A high relative water content remained (≈83%) under moderate doses (100–150 Gy) but declined 10.1% at 300 Gy, 4‰ NaCl. Na⁺ accumulation increased with rising salinity levels, whereas K⁺ concentrations decreased under high irradiation doses. A treatment of 100 Gy, 0‰ NaCl showed the largest root diameter was 595.1 µm and smallest diameter at 307.8 µm under 300 Gy combined with 4‰ NaCl. In addition, gene expression levels of OsSKC1, OsGST, and OsHAK5 showed upregulation trends under 100 Gy, suggesting improved ion homeostasis and enhanced antioxidative defense mechanisms under moderate irradiation. Overall, these findings underscore the nuanced effects of gamma radiation on rice resilience to salt stress in ‘Tai Nguyen’ rice seedlings, highlighting the importance of irradiation dose optimization for potential agricultural applications.