A Trp574 to Leu Amino Acid Substitution in the ALS Gene of Annuai Biuegrass (Poa annua) Is Associated with Resistance to ALS-lnhibiting Herbicides
ALS-inhibiting herbicides target the ALS enzyme, which controls branched chain amino acid (Val, Leu, Ile) synthesis, causing plant death. The most common mechanism of resistance in plants is a point mutation in the target gene, and 6 mutations have been associated with herbicide resistance in several weed species. Annual bluegrass is one of the most troublesome weeds, especially in the southeastern United States, and several resistant populations have recently been reported. The purpose of this study was to determine the mechanism of resistance in an annual bluegrass population from Alabama. Resistance was confirmed in the AL population compared with a susceptible population, and the ALS gene was then sequenced. The resistant population showed a mutation at Trp574, and a smaller amplicon surrounding the mutation was cloned and sequenced to look at different forms of ALS. The sequence confirmed the Trp to Leu mutation at position 574 in the ALS gene. This mutation has been shown to confer resistance to ALS-inhibiting herbicides in other plant populations, indicating that the mutation may be the cause of resistance in the AL population.
The authors sequenced 15 plaques at each stage of amplification, so the results should be reliable. The results also agree with previously published studies. The research is definitely relevant, as annual bluegrass is resistant to herbicides with many different mechanisms of action. There has not been much research into nonchemical mechanisms of control, so there may come a point where annual bluegrass has developed resistance to most or all herbicides. Recently, resistant populations have been found in Mississippi, Tennessee, and Georgia as well as the original population in Alabama.
More research should be done into nonchemical mechanisms of annual bluegrass control, as it develops resistance rapidly. Alternatively, more research could be done to develop an herbicide with a novel mechanism of action.
McElroy, J. Scott, et al. “A Trp574 To Leu Amino Acid Substitution In The ALS Gene Of Annual Bluegrass (Poa Annua) Is Associated With Resistance To ALS-Inhibiting Herbicides.” Weed Science 61.1 (2013): 21-25. Environment Complete. Web. 7 Nov. 2016.