THE IMPACT OF ECOLOGICAL ZONE ON TREHALASE ACTIVITIES IN Sitophilus zeamais POPULATIONS IN ONDO STATE

Abstract

Trehalase is an enzyme that breaks down or hydrolyzes trehalose into glucose. In this study, the impact of ecological zones on the activity of trehalase in Sitophilus zeamais was investigated. Also, the inhibitory effects of an organophosphate (DDVP) and a botanical (Eugenia aromatica) on the activities of the enzyme in the insect from selected locations (savannah, rainforest and mangrove) were studied. Samples of maize grains infested with S. zeamais were obtained from nine locations across the three ecological zones of Ondo State. The locations sampled were Mangrove Forest (Ilaje, Okitipupa, Ore), Savannah Forest (Ikare, Akungba) and Rainforest (Ondo, Akure, Owo, Ifon). Standard Methods were used to assay the enzyme activity and also to determine the concentration of protein in the samples. The highest S. zeamais trehalase activity was observed in the extreme ends of the State, Savannah in the northern part (Ikare- 0.728μmol/min/ml) and Mangrove forest in the southern part (Ilaje-0.639μmol/min/ml) while the lowest activity was observed in Ondo (0.372μmol/min/ml) which is part of the rain forest. As the concentrations of the inhibitors increased, the spatial distribution of the trehalase inhibition changes across the zones. The Savannah forest (Ikare) weevils with the highest trehalase activity were also inhibited the most by the various insecticides. From the first concentration 2.2- dichlorovinyl dimethyl phosphate (DDVP), starting from the lowest (0.00001%) to the highest (0.01%), Ikare (Savannah forest) was largely inhibited. Savannah forest has the highest temperature thereby affecting the activity of the enzyme. The results of this work show the activities of trehalase enzyme in S. zeamais in the various ecological zones of Ondo State. The results also show the impacts of inhibitors such as E. aromatica and organophosphate (DDVP) on the activity of trehalase enzymes in S. zeamais in the three ecological zones of Ondo State. Eugenia aromatica and organophosphate 2,2-dichlorovinyl dimethylphosphate (DDVP) posses insecticidal properties that can be improved / developed to curb the damaging activities of S. zeamais in storage.