Abstract: Soybean is an important source of oil, protein, and feed. However, its yield is far below that of major cereal crops. The green revolution increased the yield of cereal crops partially through high-density planting of lodging-resistant semi-dwarf varieties, but required more nitrogen fertilizers, posing an environmental threat. Genes that can improve nitrogen use efficiency need to be integrated into semi-dwarf varieties to avoid the overuse of fertilizers without the loss of dwarfism. Unlike cereal crops, soybean can assimilate atmospheric nitrogen through symbiotic bacteria. Here, we created new alleles of GmGID1-2 (Glycine max GIBBERELLIN INSENSITIVE DWARF 1-2) using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9) editing, which improved soybean architecture, yield, seed oil content, and nitrogen fixation, by regulation of important pathways and known genes related to branching, lipid metabolism, and nodule symbiosis. GmGID1-2 knockout reduced plant height, and increased stem diameter and strength, number of branches, nodes on the primary stem, pods, and seeds per plant, leading to an increase in seed weight per plant and yield in soybean. The nodule number, nodule weight, nitrogenase activity, and nitrogen content were also improved in GmGID1-2 knockout soybean lines, which is novel compared with the semi-dwarf genes in cereal crops. No loss-of-function allele for GmGID1-2 was identified in soybean germplasm and the edited GmGID1-2s are superior to the natural alleles, suggesting the GmGID1-2 knockout mutants generated in this study are valuable genetic resources to further improve soybean yield and seed oil content in future breeding programs. This study illustrates the pleiotropic functions of the GID1 knockout alleles with positive effects on plant architecture, yield, and nitrogen fixation in soybean, which provides a promising strategy toward sustainable agriculture.

Key words: genetic modification, natural variation, nitrogen fixation, plant architecture, seed oil content, soybean, yield