Generation of herbicide tolerance traits and a new selectable marker in wheat using base editing

Developing herbicide-tolerant varieties by genome editing holds great promise for addressing the worsening weed problems in wheat cultivation(1). Here, we generated transgene-free wheat germplasms harbouring herbicide tolerance mutations that confer tolerance to sulfonylurea-, imidazolinone- and aryloxyphenoxy propionate-type herbicides by base editing the acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase genes. These stackable herbicide tolerance traits provide a potentially powerful tool for weed management. In addition, we found that base editing at the wheat ALS Pro-174 codon (TaALS-P174) endowed wheat with sufficient resistance to nicosulfuron herbicide in MS growth medium to allow selection. When the TaALS-P174 editor was coupled with editors for other targets of interest, co-editing occurred in the nicosulfuron-resistant plants, and selection for resistance in growth medium enriched the frequency of coupled targets by several-fold. This selectable co-editing system has the potential to greatly bolster adoption of base editing for crop improvement applications.