Assessment of Sauromatum guttatum lectin toxicity against Bactrocera cucurbitae

Lectins are proteins that bind specifically to foreign glycans. Due to this binding property, these molecules have potential application as bioinsecticidal tools replacing conventional chemical insecticides. The present study involved purification of phytolectin from the tubers of Sauromatum guttatum by affinity chromatography on asialofetuin-linked silica matrix. The purity of the sample was checked by SDS-PAGE at pH 8.3. Purified lectin was incorporated in the artificial diet of a Dipteran model, Bactrocera cucurbitae at different concentrations (10, 20, 40, 60 and 80 µgml(-1)). The lectin significantly affected various developmental parameters that were studied. Percentage pupation and percentage emergence was reduced to 44 % and 7.9%, respectively, at 80 µgml(-1) concentration as compared to control (100%). LC50 of Sauromatum guttatum lectin was calculated to be 19.42 µgml(-1). Treatment of insect larvae with LC50 of Sauromatum guttatum lectin suppressed the activity of hydrolytic enzymes (esterases and acid phosphatases) and oxidative enzymes (superoxide dismutase and glutathione-S-transferase). Thus, with low LC50 and high mortality (approximately 92% at 80 µgml(-1)) of the insect larvae, Sauromatum guttatum lectin offers a possibility to engineer crop plants for improved and safer agriculture.