Negative effect of non-host protease inhibitors partially purified from Cassia glauca seeds on developmental physiology of Spodoptera litura

Abstract

Spodoptera litura is one of the major polyphagous pests of agro-economically important crops in Asia, Africa and Europe, causing up to 100% loss in crop production. Recent research in eco-friendly plant based insecticides has attracted the attention of researchers. In this study, protease inhibitors (PIs) from non-host plant Cassia glauca were partially purified, with 73% trypsin inhibitory activity, to assess its anti-insect potential. Larval growth and development parameters were assessed by supplementing this PI in artificial diet at various concentrations (25–800 μg/ml). Bioassay studies revealed the inhibitory potential of this PI. Increasing concentrations of PI produced a decrease in larval duration, larval weight, number of pupae formed from treated larvae, pupal weight, percentage female emergence, fecundity and percentage hatching. Food utilization experiments showed an anti-nutritional effect of PI as relative growth rate, efficiency of conversion of ingested and digested food declined in a dose response manner whereas relative consumption rate, approximate digestibility and metabolic cost increased in larvae reared on PI supplemented diet. Experiments with digestive proteases in vitro showed an inhibition in trypsin and chymotrypsin activity in the insect lumen. In conclusion, these PI proteins might be suitable for insect pest management of food crops.