Systematic, small-scale screening with Arabidopsis reveals herbicides synergies that extend to lettuce.

Abstract

Combining herbicides into a mixture is a common approach used to overcome the potential for herbicide resistance in weeds. Many herbicide mixtures can be antagonistic and they are rarely synergistic. Here, 24 commercial herbicides, each representing a different mode of action were used to create a matrix of all 276 unique combinations to search for new synergies in agar using Arabidopsis thaliana. Herbicides were used at an appropriate sublethal dose such that any synergies gave visible growth inhibition. We found five synergies including three new ones, namely mesotrione-norflurazon, mesotrione-clethodim and clomazone-paraquat. All three were reproducible in soil-grown conditions. Interestingly, the three new combinations all included a bleaching herbicide, suggesting that synergy might be a class-specific phenomenon. We also found that mesotrione-norflurazon and mesotrione-clethodim combinations were also synergistic against lettuce (Lactuca sativa), but not tef (Eragrostis tef). Our study shows that screening herbicide mixtures against A. thaliana is an efficient approach for finding rare herbicide synergies.