An EMS mutant of rice cultivar Nagina 22 exhibits tolerance to diverse abiotic stresses

Abstract

Rice frequently encounters diverse abiotic stresses under changing climatic conditions, including high temperature, osmotic stress, and nutrient deficiencies, which severely limit productivity. Nagina 22 (N22), an aus rice cultivar, is widely recognized as an important donor for drought and heat tolerance traits. However, its sensitivity to phosphorus deficiency poses a significant limitation, particularly under drought and high-temperature conditions, which further reduce the availability of inorganic phosphate (Pi). We hypothesized that mutagenesis of N22 would yield superior variants with enhanced agronomic performance and conserved stress-response mechanisms. One of the Ethyl methanesulfonate (EMS) mutants, NH733, outperformed N22 by maintaining higher photosynthetic efficiency, biomass, reproductive fertility, and grain yield, supported by a more efficient antioxidant machinery under high temperature and low-soil-phosphorus (P) conditions. RNA sequencing under diverse (osmotic stress, high temperature, and low-P) stresses revealed the potential roles of HSFA2D, PCF3, and GHD7 in broad-spectrum stress adaptation of NH733, thereby establishing this mutant line as a valuable genetic resource for breeding climate-resilient rice varieties. Functional validation of the genes and regulators identified in this study will further facilitate their exploitation in genome editing or genomic assisted breeding–driven crop improvement programs.