Derived cleaved amplified polymorphic sequence, a simple method to detect a key point mutation conferring acetyl CoA carboxylase inhibitor herbicide resistance in grass weeds

Substitution of isoleucine by leucine at the equivalent of residue 1781 of acetyl CoA carboxylase (ACCase) in Alopecurus myosuroides (I1781L) has been shown to be a key point mutation conferring resistance to most aryloxypropionate and cyclohexanedione herbicides in Lolium spp., A. myosuroides, Avena fatua and Setaria viridis. This substitution results from changing an adenine residue to either thymine or cytosine at position 5341 in the ACCase coding sequence of A. myosuroides and at the homologous position in the other species. The I1781L mutation can be detected by allele-specific amplification assays. These are, however, very dependent on the conservation of the nucleotide sequences flanking the causative single nucleotide polymorphism. Moreover, such assays cannot distinguish between homozygous and heterozygous individuals in a single polymerase chain reaction reaction. Here we present an alternative derived Cleaved Amplified Polymorphic Sequence (dCAPS) method to define I1781L status in the ACCase enzyme of four grass weeds. This dCAPS approach is simple, economical, highly transferable between species and can readily distinguish homozygous Leu/Leu 1781 and heterozygous Ile/Leu 1781 resistant individuals, providing the basis for accurate measures of the frequency of the dominant Leu allele in a given population.