A mutation in the C domain of the acetolactate synthase (ALS) gene of Bidens pilosa confers resistance to imazethapyr

摘要

A biotype of Bidens pilosa resistant to imazethapyr has been isolated and characterized. A preliminary set of whole plant and in vitro ALS assays in the presence of this herbicide strongly suggested that resistance was due to an alteration in target site by mutation. This was confirmed when the C, A, D, B and E conserved domains of the ALS were amplified. This was done by PCR using a set of universal and degenerate oligonucleotides useful for the cloning of these sequences in all plants tested to date. Several amino acid replacements were found. Some of them are either out of the five conserved domains from where mutations can confer resistance to herbicides, or are located in non-conserved regions of the gene. This suggests that these substitutionsare not responsible for the observed resistance. However, a M_(18) to T substitution, located in the D domain, was found in the resistant plants. This mutation has only been reported in resistant plants isolated in the laboratory. This is the first case of a resistant plant isolated from the wild with this same mutation.