Physiological and Molecular Responses of Diverse Rice Genotypes under Drought Stress

Abstract

Abstract Climate change-induced drought stress is a significant constraint on global rice (Oryza sativa L.) production, threatening food security. This study evaluated the drought resilience of 15 diverse rice genotypes from the USDA mini-core collection under field, greenhouse, and osmotic stress conditions. Field trials assessed reproductive-stage drought tolerance based on panicle length (PL), number of spikelets per panicle (NSP), and spikelet sterility (SS). Greenhouse experiments examined moisture retention at the vegetative stage. Significant genotypic variation was observed, with genotypes 310724, 310779, 311181, 311603, 311793, and Vandana exhibiting drought tolerance through stable PL and SS. Additionally, genotypes 310100, 310428, 311255, N22, and Bengal demonstrated superior moisture retention. The study emphasizes selecting genotypes with stable performance to enhance drought tolerance, with 310779 and N22 standing out for their low spikelet sterility and strong drought resilience. In contrast, genotypes like 311111, 311140, 311180, and KB showed heightened sensitivity to drought, with reduced panicle length, fewer spikelets, and increased sterility, making them less suitable for drought-prone environments. Under polyethylene glycol (PEG)-induced osmotic stress, Vandana, 301418, and 311140 exhibited strong tolerance, while 310428, 310724, 311111, 311180, 310779, and 311181 were sensitive. Drought-resistant genotypes exhibited increased root traits, including root length (RL), root-to-shoot ratio (RSR), total root number (TRN), and dry root weight (DRN). Further, drought-resistant genotypes Vandana, N22, 311255 and 311181 displayed an ABA-sensitive phenotype at early growth stages, with ABA-mediated signaling influencing osmotic stress tolerance. RT-qPCR analysis revealed increased ZIP gene expression in drought- tolerant genotypes following ABA application. These findings underscore the importance of stress-specific evaluations in identifying drought-tolerant genotypes. However, genotypes such as Vandana, N22, and 311255 emerged as promising candidates for breeding programs aimed at improving drought resilience in rice. The study provides valuable insights for developing climate-resilient rice varieties, integrating physiological, morphological, and genetic approaches to enhance adaptation to water-limited conditions.