Development and Breeding of Herbicide-Resistant Sorghum for Effective Cereal-Legume Intercropping

Weeds bring a serious challenge to crop production, and herbicides is the most effective and economic way to manage it in field. Sorghum is a critical crop for staple food, fodder, and biofuel. However, the lack of herbicide-resistant sorghum germplasm severely impedes its production. Here, we conducted a large-scale screening and identified 13 sorghum mutant lines resistant to imidazolinone (IMI) herbicides. Two unique mutation sites in SbALS (acetolactate synthase), thus namely Sbals-1 (A93T) and Sbals-2 (S624N) are discovered, both enhance sorghum tolerance to imazamox. Notably, under high concentrations of imazamox, sbals-1 presented a superior growth phenotype and elevated SbALS activity than sbals-2, a difference that can be attributed to the predicted protein structures. Breeding with Sbals, both grain- and grass-type sorghum, shows great weed control and field performance. The herbicide imazamox resistance is further evaluated in a soybean population for sorghum-soybean strip intercropping, identifying 123 highly resistant soybean varieties. Field intercropping tests indicated health growth of both soybean and sorghum lines post-imazamox treatment, which enhance field clearance of weed. This study, therefore, provides valuable insights not only for herbicide-resistant sorghum breeding but also for the successful implementation of efficient and sustainable cereal-legume intercropping systems.