Abstract

A lectin was purified from the tuber, Dioscorea mangenotiana in this study. The lectin agglutinated erythrocytes from human and rabbit, and the activity was inhibited by glucose and N-acetyl-D-glucosamine with minimum inhibitory concentration (MIC) of 50 and 25 mM, respectively.  The lectin was composed of two isoforms, DML I and DML II. The apparent native molecular mass of DML I was estimated at 51 kDa and the subunit molecular mass at 25 kDa, suggesting a dimeric structure. The lectin was stable up to 90°C and within the physiological pH range. The lectin when incorporated in artificial diet at concentrations of 10 to 160 µg ml^-1 and fed ad libitum to the second instar larvae of Eldana saccharina, prolonged the development period and significantly inhibited the pupation and emergence of the insect in a dose-dependent manner. The LC₅₀ calculated based on mortality after 72 h of treatment was 66.6 mg/ml. The activities of hydrolytic enzymes - acid phosphatase, alkaline phosphatase and acetylcholine esterase in the larvae reared on diet containing lethal dose of the lectin were significantly affected as compared to those fed on diet without the lectin. The results showed that DML I has promising anti-insect potential and could be employed in a biotechnological strategy for the pest management.

Key words: Lectin, tuber, anti-insect, Dioscorea mangenotiana,Eldana saccharina.