Patent ID: 8206906

Claim:
A method for detecting a variant allele of a plant acetohydroxyacid synthase large subunit (AHASL) gene that confers tolerance to imidazolinone herbicides on the plant, said method comprising the steps of: (a) obtaining genomic DNA from the plant; (b) using said DNA as a template for a PCR amplification comprising said DNA, polymerase, deoxyribonucleotide triphosphates, a forward AHASL-gene-specific primer, a reverse AHASL-gene-specific primer, and a variant-allele specific primer comprising a nucleotide sequence with a 5′ end and a 3′ end, wherein said nucleotide sequence is capable of annealing to the complement of nucleotides 3 to 23 of SEQ ID NO:12, wherein the 3′-end nucleotide of said nucleotide sequence is cytidine, wherein said cytidine is at the position that corresponds to the site of a G-to-A substitution that gives rise to an S653(At)N substitution in an AHASL protein; and (c) detecting a product of said PCR amplification, said product corresponding to the region of said AHASL gene bounded by the annealing sites of the variant-allele specific primer and the reverse AHASL-gene-specific primer on said AHASL gene, wherein detecting said product indicates the presence of a variant allele of the plant AHASL gene; wherein said variant-allele specific primer is 20 nucleotides or more in length and is capable of annealing to a region of an AHASL gene that is nested between the annealing sites of said forward and reverse AHASL-gene-specific primers.