Engineering herbicide-resistant maize using chimeric RNA/DNA oligonucleotides

Maize plants resistant to imidazolinone herbicides were engineered through targeted modification of endogenous genes using chimeric RNA/DNA oligonucleotides. A precise single-point mutation was introduced into genes encoding acetohydroxyacid synthase (AHAS), at a position known to confer imidazolinone resistance. Phenotypically normal plants from the converted events (C-0) were regenerated from resistant calli and grown to maturity. Herbicide leaf painting confirmed the resistance phenotype in C-0 plants and demonstrated the anticipated segregation pattern in C-1 progeny. DNA cloning and sequencing of the targeted region in resistant calli and derived C-0 and C-1 plants confirmed the expected mutation. These results demonstrate that oligonucleotide-mediated gene manipulation can be applied to crop improvement. This approach does not involve genomic integration of transgenes. Since the new trait is obtained through modifying a gene within its normal chromosomal context, position effects, transgene silencing, or other concerns that arise as part of developing transgenic events are avoided.