Abstract
Creeping bentgrass (Agrostis stolonifera L.) is moderately tolerant to the p-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide topramezone. However, the contribution of plant metabolism of topramezone to this tolerance is unknown. Experiments were conducted to determine if known cytochrome P450 monooxygenase inhibitors 1-aminobenzotriazole (ABT) and malathion alone or in combination with the herbicide safener cloquintocet-mexyl influence creeping bentgrass tolerance to topramezone. Creeping bentgrass in hydroponic culture was treated with ABT (70 μM), malathion (70 μm and 1000 g ha-1), or cloquintocet-mexyl (70 μM and 1000 g ha-1) prior to topramezone (8 g ha-1) application. Topramezone-induced injury to creeping bentgrass increased from 22% when applied alone to 79 and 41% when applied with malathion or ABT, respectively. Cloquintocet-mexyl (70 μM and 1000 g ha-1) reduced topramezone injury to 1% and increased creeping bentgrass biomass and PSII quantum yield. Cloquintocet-mexyl mitigated the synergistic effects of ABT more than those of malathion. The effects of malathion on topramezone injury were supported by creeping bentgrass biomass responses. Responses to ABT and malathion suggest that creeping bentgrass tolerance to topramezone is influenced by cytochrome P450-catalyzed metabolism. Future research should elucidate primary topramezone metabolites and determine the contribution of cytochrome P450 monooxygenases and glutathione S-transferases to metabolite formation in safened and non-safened creeping bentgrass.
Highlights
Creeping bentgrass (Agrostis stolonifera L.) is the most widely used cool-season turfgrass on golf course fairways and tees in the United States [1]
Reductions in leaf tissue biomass, concomitant with increases in visible bleaching and necrosis caused by malathion, suggests that P450 monooxygenase function influences topramezone metabolism in creeping bentgrass
Previous research investigating metabolism-based chlorsulfuron resistance in Lolium rigidum found that malathion increased chlorsulfuron toxicity more than ABT [42]
Summary
Creeping bentgrass (Agrostis stolonifera L.) is the most widely used cool-season turfgrass on golf course fairways and tees in the United States [1]. Gaertn.), and bermudagrass (Cynodon spp.) are difficult-to-control weeds. P450 Inhibitors Reduce Bentgrass Tolerance to Topramezone that disrupt the functional and aesthetic quality of creeping bentgrass turf [2]. Herbicide options for weed control in creeping bentgrass are limited. Herbicides such as fenoxaprop-pethyl and quinclorac often cannot be applied at rates that provide acceptable weed control as they are too injurious to creeping bentgrass [3,4,5,6,7,8]
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