Identification and Characterization of a Permethrin Resistance Mechanism in Populations of the Fungus GnatLycoriella Mali(Fitch) (Diptera: Sciaridae)

Abstract

The commercial mushroom pestLycoriella mali(Fitch) (Diptera: Sciaridae) has evolved resistance to the adulticide permethrin. Preliminary investigations have indicated that oxidative metabolism was the most likely resistance mechanism. Monooxygenase activity (dealkylation reactions) against model substrates was used to examine specific metabolic activity associated with resistance. Differences in monooxygenase activity reflected resistance ranking of the field populations. The most resistant population was determined, by carbon monoxide difference spectrophotometry, to have a 1.7-fold greater level of cytochrome P-450 compared to the next most resistant population. This finding suggested that the quantity of enzyme was not solely responsible for variation in resistance. Enzyme kinetics were used to compare variation in metabolism of two model substrates, tetramethylbenzidine andpara-phenylenediamine, between populations. The enzyme preparation from the most resistant population had a higher affinity for both model substrates. This suggested that this population possessed a different monooxygenase and that this enzyme was more active in metabolizing the model substrates.