Enhancement of glyphosate efficacy on Amaranthus palmeri by exogenous quinate application

Abstract

Glyphosate is a widely used herbicide targeting the enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) in the aromatic amino acid biosynthesis pathway (shikimate pathway) and provoking accumulation of quinate, a secondary metabolite synthesized through a side branch of this pathway. The objective of this work was to evaluate whether the efficacy of glyphosate activity in Amaranthus palmeri is enhanced by quinate application one day after herbicide treatment. To this end, one glyphosate-sensitive and one glyphosate-resistant (due to EPSPS gene amplification) population of A. palmeri were used. The 3- day time course study of the quinate treatment alone showed quinate, Tyr and Phe accumulation in both populations. When the herbicide was applied alone at 0.25× the recommended dose, no phytotoxicity or glyphosate effects were detected in the sensitive population 3 days after treatment, but the combined treatment with quinate was lethal, and markers of herbicide activity at the amino acid level could be detected. In the resistant population, an important metabolic perturbation in the flux of the shikimate pathway was detected in the combined treatment. These results raise the possibility of the joint application of quinate and glyphosate to enhance glyphosate efficacy while lowering doses in the sensitive population.