Alpha-amylase inhibitor from local common bean selection: Effect on growth and development of Corcyra cephalonica

Abstract

Cultivars of common bean (Phaseolus vulgaris L.) from the Kalpa valley of the Kinnaur district were screened for alpha-amylase inhibitor activity against porcine pancreatic α-amylase and significant differences were found amongst them. The inhibitor protein was partially purified from Triloki cultivar by ammonium sulphate precipitation and Sephadex G-100 gel filtration chromatography. Inhibitor protein was non-competitive, heat labile and retained 55.51 per cent activity at 70 °C. It had two pH optima of 5.0 and 7.6. Inhibitor protein inhibited amylases of 3rd -4th instar larval extracts of Corcyra cephalonica Stainton, the rice moth. C. cephalonica larvae (3rd -4th instar) were fed on wheat flour mixed with 0.013 percent (w/w) of partially purified α-amylase inhibitor protein. The growth of larvae in the treatment was significantly reduced. Treated larvae showed 100 percent mortality after 11 days. In the untreated control, no larval mortality was observed and adults emerged after 45 days. The inhibitor protein was effective at very low concentrations and could be exploited for control of this grain storage pest.