Comparison of α- and β-mannosidase activity in the three cereal pests, Haplothrips tritici Kurdjumov (Thysanoptera: Phlaeothripidae), Rhopalosiphum padi L. (Homoptera: Aphididae) and Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Abstract

The Sunn pest, Eurygaster integriceps, the bird cherry-oat aphid, Rhopalosiphum padi, and wheat thrips, Haplothrips tritici are the major pests of wheat and other cereals in a wide area of the world. All these three insect species could produce damage to the wheat to some extent. Therefore, the purpose of the present study was to determine α- and β-mannosidase of the three mentioned insect pests. These insects were collected from the wheat farm and their guts (the Sunn pest and the aphid) and salivary glands of Sunn pest were removed. However, regarding tiny body of thrips, the whole body used in order to extract the enzymes. The enzymes, including α- and β-mannosidase activity, were measured by the hydrolysis of p-nitrophenyl-α-d-mannopyranoside (pNPαGal) and p-nitrophenyl-β-d-mannopyranoside (pNPβGal), respectively, using phosphate citrate buffer (pH 5.0). Mannosidases were not active in all three tested insect species, and also there were significant differences in activities of the two enzymes in three species. The greatest activity of α-mannosidases was observed in the Sunn pest salivary glands, E. integriceps, and the least activity was found in Sunn pest midgut with no activity. However, the activity of β-mannosidase was established in Sunn pest midgut, but there was no activity in the aphid midgut, R. padi. Activities of these two enzymes were modest in the thrips, H. tritici. The greatest amount of β-mannosidases in the Sunn pest midgut makes sense, since the Sunn pest is the main pest in the wheat farm that can feed on wheat grains. In the wheat grains, the highest amount of glycoproteins and glycolipids are present. Thus, it has been known that these enzymes (α- and β-mannosidases) are active on digestion of carbohydrates.