SEARCH FOR VEGETATIVE INSECTICIDAL PROTEINS (VIPS) FROM LOCAL ISOLATES OF BACILLUS THURINGIENSIS EFFECTIVE AGAINST LEPIDOPTERAN AND HOMOPTERAN INSECT PESTS

Abstract

ABSTRACT Certain strains of Bacillus thuringiensis (Bt) have shown to produce secretary proteins during their vegetative growth phase. In recent years, these proteins have shown remarkable insecticidal properties against several lepidopteran and coleopteran pests, and were named as vegetative insecticidal proteins (VIPs). Wide spread use of transgenic Bt crops which produces the well known insecticidal crystal protein (ICP) of Bt has increased the chances of resistance among pests. In this situation, the advent of the VIP is considered as a possible way to overcome the limitations of the first generation Bt toxins. The current study is aimed to search for novel VIPs or VIP-like proteins with effect towards several economically important pests that could not be controlled by the ICPs. A fairly large number of Bt isolates were screened in order to find a suitable VIP-like protein that might offer novelty in their insect mortality potential and newer sensitivity range amongst the target insects to be used in future transgenic approach. The toxic protein from the different strains were isolated and partially purified, and the susceptible insects from the lepidopteran and homopteran group were confirmed through bioassay. We were able to identify two VIP toxins; one was found to be effective against lepidopteran pests and the other to be effective against homopteran insect pests. This is the first study demonstrating activity of a Vip toxin against homopteran pests.