Herbicide-Resistant Plants from Cultured Cells

Summary

Tobacco mutants resistant to sulphonylurea herbicides were isolated by selection in cell culture. Resistance resulted from mutations in either of two unlinked genes encoding isozymes of the branched chain amino acid biosynthetic enzyme, acetolactate synthase (ALS). These mutant alleles directed the synthesis of forms of ALS with greatly reduced sensitivity to inhibition by sulphonylurea herbicides. The cloning and transfer of these mutant alleles encoding herbicide-insensitive forms of ALS will provide an efficient and powerful method by which to introduce herbicide resistance into presently susceptible crop species.