Salicylic Acid Improves Rice Seed Germination under Induced Drought Stress

IntroductionR ice is one of the most important food commodities and provides major portion of daily calories requirement, especially in underdeveloped and developing countries (Fukagawa and Ziska, 2019).The world population is increasing at an exponential rate, demanding approximately 70% increase in food production to meet the food security targets by 2050 (Fróna et al., 2014).Water scarcity or drought is one of the biggest threats to food security worldwide and could reduce crop production by 50% (Budak et al., 2015).Therefore, management of drought stress is crucial for successfully achieving the desired production targets.About 77% of the total cultivated rice is conventionally transplanted globally Abstract | Rice is the staple food of more than 50% of the world's population, and water scarcity is threating its sustainable production.Dry seeded rice (DSR) technology has water and labour saving advantages over conventional transplanting culture, however, poor crop establishment due to reduced germination in variable field conditions greatly hampers its large-scale adaption.To address subordinate germination issues, we investigated the effects of five salicylic acid (SA) concentrations (0, 75, 150, 225 and 300 ppm) on polyethylene glycol (PEG) induced drought stress conditions (0, -0.2, -0.4,-0.6 and -0.8 MPa).Highly significant (p < 0.01) effects of drought, SA and their interactions were observed on seed germination.Interestingly, varying SA concentrations imparted more pronounced effects under higher osmotic stress levels.Day-wise germination data indicated that the SA treatments alleviated inhibitory effects of different osmotic stress levels after 2-4 days of stress applications.Under medium to high osmotic stress levels, mean germination time, germination index and seed vigour index (SVI) of SA primed seeds were better than non-primed seeds.Remarkably, SVI of all SA concentrations under -0.2 MPa osmotic stress was surprisingly improved as compared with control and other osmotic stress levels, indicating a 'drought-escape strategy' in rice seeds under low osmotic stress level.Overall, our results indicated that seed priming with 225 ppm SA concentration is ideal under all environments and should be recommended in DSR system to improve early crop establishment and sustainable production.