Creation of dual-purpose soybean germplasm for grain and forage by CRISPR/Cas9-mediated targeting mutation of GmFT2a and GmFT5a.

Soybean [Glycine max (L.) Merr.] seeds are a rich source of high-quality protein and edible oil, and their foliage supports the rearing of the economically significant insect, 'Doudan'. This study utilized CRISPR/Cas9 to edit the GmFT2a and GmFT5a genes, resulting in soybean germplasm with enhanced grain and forage traits. Under short-day conditions, the double mutant ft2a ft5a showed significant increases in grain yield and yield-related traits, including main stem nodes, branching, and pod count per plant. Under long-day conditions, the double mutant exhibited a substantial increase in total vegetative biomass, with prolonged vegetative growth, larger leaves, and increased branching and nodes. The soluble protein and soluble sugar contents remained unchanged, while phenylalanine levels increased and tannin content decreased, which is beneficial for Doudan feeding. The ft2a ft5a double mutant is suitable for both grain and forage soybeans. We further revealed the molecular basis for the influence of GmFT2a and GmFT5a on soybean architecture. GmFT2a and GmFT5a proteins interact with each other and with Dt2 and SOC1a critical genes for branching and stem growth in soybeans. This interaction forms a complex that potently activates the downstream GmAp1s gene expression. The simultaneous mutation of GmFT2a and GmFT5a significantly downregulates GmAp1s expression, impacting soybean plant architecture. Overall, this study not only identifies the dual role of GmFT2a and GmFT5a in soybean yield and biomass but also uncovers their molecular interactions with Dt2 and SOC1a, providing a foundation for the genetic enhancement of soybean varieties tailored for both grain and forage production, underscoring the potential for improving agricultural sustainability and economic value.