A quantitative trait locus, qSE 3, promotes seed germination and seedling establishment under salinity stress in rice

Summary Seed germination is a complex trait determined by both quantitative trait loci (QTLs) and environmental factors and also their interactions. In this study, we mapped one majorQTLqSE3for seed germination and seedling establishment under salinity stress in rice. To understand the molecular basis of thisQTL, we isolatedqSE3by map‐based cloning and found that it encodes a K+transporter gene,OsHAK21. The expression ofqSE3was significantly upregulated by salinity stress in germinating seeds. Physiological analysis suggested thatqSE3significantly increased K+and Na+uptake in germinating seeds under salinity stress, resulting in increased abscisic acid (ABA) biosynthesis and activatedABAsignaling responses. Furthermore,qSE3significantly decreased the H2O2level in germinating seeds under salinity stress. All of these seed physiological changes modulated byqSE3might contribute to seed germination and seedling establishment under salinity stress. Based on analysis of single‐nucleotide polymorphism data of rice accessions, we identified aHAP3 haplotype ofqSE3that was positively correlated with seed germination under salinity stress. This study provides important insights into the roles ofqSE3in seed germination and seedling establishment under salinity stress and facilitates the practical use ofqSE3in rice breeding.