Abstract

Biochemical and feeding assays were performed in order to assess the bioactivity of trypsin inhibitors from sesame seeds to control Plodia interpunctella larvae. The biochemical assays were based on the ability of protease inhibitors (PI) present in sesame seeds to inhibit bovine pancreatic trypsin and digestive enzymes of insect larvae. The stability of the inhibitors was also assessed at different pH and temperature. The feeding bioassays were carried out in plates containing second instar larvae fed on diet with sesame protein extract. It was observed that all genotypes presented inhibition when tested with BPT, ranging from 51 to 90%, among them BRS Seda, CNPA G3 and CNPA G4 showed average of 69% of inhibitory activity for intestinal homogenate. The FII-fractions in these three genotypes showed thermal and pH stabilities at 40°C and 8.5, respectively. In feeding bioassay, P. interpunctella larvae were susceptible to SPCE of all three genotypes, revealing average mortality of 74% to SPCE and 45% to FII-fractions. Among all genotypes, BRS Seda was more effective to inhibition of digestive enzymes of insects and considered the more suitable genotype for further using in sesame breeding program to resistance to P. interpunctella.

Key words: Sesamum indicum L., serine protease, stored grain pest, Lepidoptera.