ISOLATION AND IDENTIFICATION OF NOVEL LOCAL ISO- LATES OF Bacillus thuringiensis ACTIVE AGAINST RED PALM WEEVIL (RPW)

Abstract

The gram-positive bacterium B. thuringiensis is well-known as sources of insecticidal proteins, most of which accumulate in crystalline inclusions during sporulation, these parasporal inclusions contain various types of insecticidal crystal protein (ICP). The crystal proteins from B. thuringiensis are among the most successful biological control agents for the suppression of agriculturally and medically important insect pests (Roh et al., 2007), being toxic to the larvae of lepidopteron, dipteran, and coleopteran insects (Johnson et al., 1998), as well as certain hymenoptera, homoptera, and mallophaga, in addition to many nematodes, flatworms, and Sarcomastigophora (Walters and English, 1995; Horak et al., 1996).
At present, more than 130 B. thuringiensis crystal proteins have been described based on their gene sequences and amino acid homologies (Crickmore et al., 1998). Recently, all crystal proteins show some relatedness is grouped into four main groups. B. thuringiensis isolates are distributed worldwide, and more than 60,000 have already been collected by various industries in an effort to obtain novel crystal proteins (Martin and Travers 1989; Li et al., 2007). In addition, B. thuringiensis isolates showing different crystal protein gene patterns from the reference strains have also been reported (Li et al., 2002).
The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier), a concealed tissue borer, is a lethal pest of palms and is reported to attack 17 palm species worldwide. Although the weevil was first reported on coconut (Cocos nucifera) in South Asia during the last two decades it has gained a foothold on date palm Phoenix dactylifera in several Middle Eastern countries from where it has moved to Africa and Europe, mainly due to the movement of infested planting material. In the Mediterranean region, RPW also severely damages Phoenix canariensis. Infested palms, if not early detected and treated, often declined and die. However, palms in the early stages of infestation usually respond to chemical insecticide treatments. RPW has been managed in several countries through an integrated pest management (IPM) program (Faleiro, 2006). The search for effective natural enemies (biological control) for RPW still continues.
A novel Bacillus thuringiensis strain, NCIMB 40152, was isolated from dead Tenebrio molitor L. Larvae. The isolate is endowed with specific insecticide activity against the Colorado potato beetle (Leptinotarsa decemlineata (Say), Coleoptera, Crysomelidae), but has no effect against lepidopteran or dipteran insects (Cidaria et al., 1991). Bacillus thuringiensis strains C-4, C-9, GM-7, and GM-10, with high toxicity against lepidopteran and coleopteran pests have been isolated from Northeast Mexico (Tamez-Guerra et al., 2004).
Bacillus thuringiensis soil isolates A21, A51 and C17 isolated from different regions of the Cuban archipelago showed higher larvicide activity than Bactivec's isolated reference strain, against both Aedes aegypti and Culex quinquefasciatus (González et al., 2011). Accordingly, This study describe the isolation and identification of novel isolates of B. thuringiensis, in order to study insecticidal activity of isolates produced proteins against Red Palm Weevil insect.