Herbicide resistance in wild grasses is a growing challenge to sustainable wheat production around the world and in the United Kingdom, results in up to 20% losses in cereal production. Resistance to selective herbicides can arise from two major mechanisms, namely target site resistance (TSR) and non-target site resistance (NTSR). TSR results from gene mutations in proteins targeted by herbicides, such as acetolactate synthase and acetyl CoA carboxylase, that render the enzyme less sensitive to chemical inhibition. TSR is now widespread in problematic wild grasses such as annual rye grass (<i>Lolium rigidum</i>) and black grass (<i>Alopecurus myosuroides</i>), conferring high levels of tolerance to specific classes of herbicide chemistries and detectable by DNA based diagnostics testing for the respective gene mutations. In contrast, NTSR is a complex quantitative trait resulting from the enhanced expression of multiple protective proteins, notably those involved in herbicide detoxification. As a quantitative trait, NTSR confers different levels of resistance to multiple selective herbicide chemistries and unlike TSR, cannot be countered by rotating different modes of action. While NTSR is dependent upon multiple proteins, our recent research has identified a single phi (F) class glutathione transferase (GSTF1) as a quantitative biomarker of this class of resistance in several wild grass species including black grass, Lolium sp. and wild oat in populations sampled from Europe, Canada and Australia. Using specific antibodies to GSTF1, we have developed a rapid immunodiagnostic, based on lateral flow technology, to detect the levels of expression of this protein that can predict the presence of NTSR in wild grass populations. Utilising DNA-based diagnostics to detect TSR and immunodiagnostics to quantitatively determine NTSR we now have the technology to rapidly assess the resistance status of wild grasses to major selective herbicides used in weed control in wheat. Drawing parallels with clinical diagnostics, these tools now offer the potential to direct the most effective control strategies prior to chemical application as well as actively monitoring the effectiveness of resistance control management measures. As such, rapid resistance diagnostics can play an increasingly important role in the stewardship of existing products, evaluating the effectiveness of weed management strategies and improving the sustainability of herbicide use in broad acre crops.

Improving sustainability in chemical weed control: applications for rapid diagnostics in herbicide resistance management

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ACS Fall 2022

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