Biochemical response of malathion-resistant and -susceptible adults of Rhyzopertha dominica to the sublethal doses of deltamethrin

Rhyzopertha dominica,lesser grain borer both in larval and adult forms is a primary pest of stored grains and mainly attack wheat,rice,millet and corn. various recommended insecticides are routinely used to control its population which has led to the development of resistance. the aim of present study was to determine the biochemical differences in the malathion-resistant and -susceptible adult populations of r. dominica. sublethal doses of deltamethrin were applied at 1.50 ppm for resistant and 0.966 ppm for susceptible populations for a period of 48 h. highly significant rise in activities of acid phosphatase (acp) (135%),amylase (55%),glutamate oxaloacetate transaminase (513%),trehalase (348%) and concentration of trehalose (110 %) was observed in susceptible population. in resistant population alkaline phosphatase (33%),amylase (40%),glutamate pyruvate transaminase (32%) and trehalase (62%) activities and concentrations of glucose (32%) decreased significantly,while free amino acids (23%),total lipids (39%),and rna (29%) content increased significantly after deltamethrin treatment. cholinesterase and acp activities increased in both populations. of respiratory enzymes,lactate dehydrogenase remained unaffected in both populations but isocitrate dehydrogenase (icdh) activity showed significant increase (87%) in resistant and decrease (81%) in susceptible populations. similarly,contrasting trend was found in amylase and trehalase activities with significant decrease in resistant and increase in susceptible population. total lipids and rna content showed rise in resistant and decline in susceptible beetles. all these biochemical changes,especially in amylase,icdh,trehalase,glucose,total lipids and rna in susceptible and resistant beetles are indicative of development of severe disturbances in respiration,carbohydrate,lipid and protein metabolism. it can be concluded that deltamethrin at above sublethal concentrations produced significant metabolic alterations by hitting at different secondary targets in resistant and susceptible populations that render the beetles unable to survive long. copyright © 2014 zoological society of pakistan.