Agronomical selection on loss‐of‐function of GIGANTEA simultaneously facilitates soybean salt tolerance and early maturity

Salt stress and flowering time are major factors limiting geographic adaptation and yield pro-ductivity in soybean (Glycine max). Although improving crop salt tolerance and latitude adap-tation are essential for efficient agricultural pro-duction, whether and how these two traits are integrated remains largely unknown. Here, we used a genome-wide association study to iden-tify a major salt-tolerance locus controlled by E2, an ortholog of Arabidopsis thaliana GIGANTEA (GI). Loss of E2 function not only shortened flowering time and maturity, but also enhanced salt-tolerance in soybean. E2 delayed soybean flowering by enhancing the transcription of the core flowering suppressor gene E1, thereby re-pressing Flowering Locus T (FT) expression. An E2 knockout mutant e2CR displayed reduced ac-cumulation of reactive oxygen species (ROS) during the response to salt stress by releasing peroxidase, which functions in ROS scavenging to avoid cytotoxicity. Evolutionary and pop-ulation genetic analyses also suggested that loss-of-function e2 alleles have been artificially selected during breeding for soybean adaptation to high-latitude regions with greater salt stress. Our findings provide insights into the coupled selection for adaptation to both latitude and salt stress in soybean; and offer an ideal target for molecular breeding of early-maturing and salt-tolerant cultivars.