The Inhibitory Activity of Triticale, Rye and Black Nightshade Seed Proteinaceous Extracts against Potato Tuberworm Digestive α-Amylase and Protease

Potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera; Gelechiidae) is a worldwide pest of solanaceous crops. Larvae feed inside galleries in foliage, stems and tubers making chemical control unsuccessful, so other control methods should be applied. In recent years many plants have received genes that encode toxic proteins as a strategy to resist insect pests. In this study, optimal pH and temperature of digestive α-amylase and protease activities of potato tuberworm and the effect of triticale (X Triticosecale wittmack cv. Sanabad), rye (Secale cereale L. cv. Danko) and black nightshade (Solanum nigrum L.) seed proteinaceous extracts against enzymes activities were evaluated using starch 1% and azocasein 2% as a substrate, respectively. The optimum pH of α-amylase and protease activities was found to be highly alkaline. Enzymes inhibition assays showed that amylase activity was significantly affected by extracts from triticale and rye by pH (P= 0.05; maximum effect at pH 9) and influencing of protease activity by extracts mentioned above did not vary by pHs 8-11 and 9-11, respectively. Extracts from black nightshade seed had no effect on enzymes activity. Inhibition manner of various concentrations; 1.5, 0.75, 0.375, 0.187 and 0.093 (mg protein ml-1) of extracts were dose-dependent. Maximum inhibitory effect occurred at the highest concentration and the minimum was at the lowest concentration. In polyacrylamide gel assay, both enzymes, without inhibitors showed two isozymes, which at highest concentration of extracts, both bands disappeared or their intensity decreased. So, these proteins can be introduced to be encoded in producing resistant potato crops against potato tuberworm.