Enhanced Activities of Metabolic Enzymes Associated with Insecticide Resistance in Red Flour Beetle (Tribolium castaneum Herbst)
Enhanced Activities of Metabolic Enzymes Associated with Insecticide Resistance in Red Flour Beetle (Tribolium castaneum Herbst)
Muhammad Asam Riaz1, Javeria Choudhary1, Muhammad Zeeshan Majeed1*, Muhammad Afzal1, Sohail Ahmed2 and Muhammad Sajjad Khalil1
ABSTRACT
The mechanism of resistance was determined in four different field populations of red flour beetle (Tribolium castaneum) collected from Faisalabad (Fsd-strain), Jhang (Jh-strain), Sahiwal (Swl-strain) and Sargodha (Sgd-strain) districts of Pakistan. Bioassays with two frequently used insecticides, i.e. deltamethrin and permethrin and one biological insecticide, spinosad, were performed on these strains of T. castaneum. Toxicological studies demonstrated that Fsd-, Jh- and Swl- strains exhibited higher tolerance ratio of 26.5-fold, 21-fold and 18.6-fold respectively relative to Sgd-strain against deltamethrin, whereas, these strains did not have significantly higher tolerance ratio against permethrin and spinosad except Fsd-strain with 9.5-fold tolerance ratio against permethrin. Biochemical studies indicated that Swl-strains had significantly higher activities of cellulases. Enzyme kinetics results demonstrated that Swl-strain had a maximum value of Vmax (68.4 Nm s-1) and lowest value of Km (12.8 g L-1). Fsd- and Swl-strains exhibited increased activities of amylases with Vmax value of 2.68 and 1.89 µM s-1 respectively and Km value of 23.8 g L-1 and 40.1 g L-1, respectively. These findings suggest that the increased activities of cellulases and amylases may play a major role in mitigating fitness-cost associated with insecticide resistance.
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