Resistance of ryegrass (Lolium spp.) to paraquat and glyphosate in the Western Cape

[摘要] ENGLISH ABSTRACT: The origin of this study dates back to 2001 when ryegrass (Lolium spp.) from avineyard near Tulbagh was found by the author to be resistant to glyphosate. Severalother populations of glyphosate resistant ryegrass were found on nearby farms. Inattempts to eliminate what was initially thought to be a very localised resistanceproblem, paraquat was applied at several of these sites. It soon became apparent thatsignificant numbers of these ryegrass populations were also resistant to paraquat.Populations that were susceptible to glyphosate but resistant to paraquat were alsofound. This was the first recorded incidence of paraquat resistance in ryegrass. Furtherscreening of Western Cape ryegrass resulted in the identification of populations thatshowed multiple resistance to glyphosate, paraquat and ACCase inhibitors.In laboratory trials this study established that the mechanism which confers resistanceto paraquat is based on the failure of the herbicide to reach its site of action in theplant. This lack of trans location was ascribed to sequestration of the active ingredientin a non-physiologically active site in the plant, such as the vacuole. This form ofresistance was overcome by applying glufosinate ammonium, either prior to, ortogether with the paraquat application. The same degree of synergy was observedusing photosystem II inhibitors with paraquat. The resistance mechanism is overcomeby these products by either preventing paraquat from being 'sequestrated and/orfreeing up of herbicide which had already been bound. Mixtures containing paraquat,glufosinate ammonium and a photosystem II inhibitor such as terbuthylazine gave thebest control of resi~tant ryegrass populations.Independent confirmation, of the findings in the laboratory perfonned trials, was donein field trials, conducted during the 2007 season by Syngenta SA on paraquat resistantryegrass populations in the Western Cape.

[发布机构] Stellenbosch University