Glutathione transferase plays a major role in flufenacet resistance of ryegrass (Lolium spp.) field populations.

BACKGROUND Herbicides inhibiting the synthesis of very long-chain fatty acids (HRAC group K-3, WSSA group 15), such as flufenacet, play an important role in weed management strategies, particularly when herbicide resistance to inhibitors with other modes of action, such as acetolactate synthase or acetyl coenzyme A carboxylase (ACCase), has already evolved. So far, only a few cases of resistance towards inhibitors of the synthesis of very long-chain fatty acids have been described. In this study, we characterized the level of flufenacet resistance in several Lolium spp. field populations and investigated the resistance mechanism. RESULTS The screening for flufenacet resistance revealed the ability of Lolium spp. populations from several continents to survive flufenacet treatments at and above the field rate. This study demonstrates the way in which flufenacet is detoxified in resistant weed populations. Glutathione was found to be conjugated to flufenacet in Lolium spp. seedlings, and there was evidence that glutathione transferase activity was enhanced in protein extracts from flufenacet-resistant seedlings. A significant correlation was found between the resistance factor obtained by biotests and the degradation half-time of flufenacet in ryegrass plants obtained by high-performance liquid chromatography (HPLC). CONCLUSION At present, flufenacet resistance is not widespread; however, in certain Lolium spp. populations resistance levels could reach agronomic relevance due to detoxification by glutathione transferases. In Europe especially, only a few herbicide modes of action are registered for the control of Lolium spp. and therefore it is becoming increasingly important to apply best management practices to prevent the spread of flufenacet resistance. (c) 2019 Society of Chemical Industry