Induction of Water-Deficit Tolerance in Rice through Gamma Mutagenesis

Abstract

Rice is a strategic crop essential for Egyptian national food security; however, climate change and escalating water scarcity pose severe threats to its sustainable production. From this point, gamma rays with its safe doses were used to genetic improvement in the Egyptian rice cultivar (Sakha 102) and for elicitation five rice mutants classified as highly drought tolerated besides, its high yielding. The six rice accessions were evaluated across two growing seasons under normal and drought conditions. Yield components, physiological and biochemical attributes besides, water stress tolerance indices were the most important parameters tested under both treatments for screening the highest rice genotypes tolerated to drought stress under stress conditions. Results indicated that significant genetic variability (P < 0.01) was observed for all physiological and yield traits. Furthermore, drought stress severely
reduced yield components, particularly in the local cultivar "Sakha 102" (DSI > 1.87; YR: 0.27). Conversely, induced mutagenesis significantly improved drought resilience. Also, mutant 5 demonstrated superior tolerance, maintaining the highest grain yield (51.68 g) and 1000-grain weight (36.97 g) under stress by maximizing glycine betaine (77.68) and trehalose (60.45) accumulation. As
well, strong positive correlations were confirmed between osmoprotectants and yield attributes under stress, notably between proline and 1000-grain weight (r = 0.96). Further, high broad-sense heritability (> 70%) coupled with high genetic advance (18.59% - 26.45%) for grain yield under stress confirmed the governance of additive gene action. Ultimately, these findings identify Mutant 5 as a high-potential donor line and validate biochemical osmoprotection as a reliable selection criterion, offering a vital genetic tool to secure future rice production amidst future climatic challenges like high level of drought stress.