Physiological mechanism of contrasting rice genotypes response to salt stress

Abstract Background Salinity is one of the major constraints to rice production. Salt sensitive and tolerant rice genotypes response large difference to salt stress. However, the physiological mechanism is still unclearly. Methods This study aimed to elucidate the physiological mechanism of contrasting rice genotypes response to salt stress. Six contrasting rice genotypes including three salt-tolerant (DJWJ, JFX, NSIC) and three salt-sensitive rice genotypes (HKN, XD2H, HHZ) were grown under two different salt concentrations (0 and 100 mmol NaCl solution) in green house. The salt stress was treated at tillering stage for 7 days. Results The results showed that growth, physiological traits and yield formation of both salt sensitive and tolerant rice were significant affected by salt stress. In general, plant height, tiller number, dry weight and relative growth rate showed 15.7%, 11.2%, 25.2% and 24.6% more reduction in salt-sensitive rice than that in salt-tolerant rice, respectively. On the contrary, antioxidant enzyme activity (SOD, POD, CAT) and osmotic adjustment substances (soluble protein, MDA) significant increased under salt stress, and the increase was far higher in salt-tolerant rice except MDA. Furthermore, grain yield and yield components significant decreased under salt stress. Overall, the salt-sensitive rice genotypes showed 15.3% more reduction in grain yield, 5.1% in spikelets per panicle, 7.4% in grain filling percentage and 6.1% in grain weight than salt-tolerant genotypes under salt stress. However, a modest gap showed in panicles (22.2% vs 22.8%) and total spikelets (45.4% vs 42.1%) decline between salt-sensitive and salt-tolerant rice under salinity condition. Conclusion This study revealed that the yield advantage of salt-tolerant rice was partially caused by more biomass accumulation, growth rate and strong antioxidant capacity and osmotic adjustment ability under salt stress, which contributed to a big panicle (more spikelets per panicle), high grain filling percentage and grain weight. The results of this study could be helpful to understand the physiological mechanism of contrasting rice genotypes response to salt stress and to be breeding of salt-tolerant rice.