A Method of Controlling Corn Rootworm Feeding Using a Bacillus thuringiensis Protein Expressed in Transgenic Maize

Abstract

uses a variant Bt Cry3Bb1 insecticidal protein (Donovan et al., 1992). Cry3Bb1 is known to be biologically active The corn rootworm (CRW; Diabrotica spp.) is one of the most against several species within the Coleopteran family serious pests of corn in the USA. Chemical insecticides and crop rotation have been the only two options available to growers for Chrysomelidae, including the western corn rootworm, managing CRW. Unfortunately, both of these tactics can be ineffective Diabrotica virgifera virgifera LeConte (Rupar et al., as a result of either resistance or behavioral modifications. In this 1991). The biological activity of this protein against D. paper, we describe transgenic maize (Zea mays L.) hybrids that control virgifera virgifera suggested its potential use in creating CRW. These hybrids were created with a Cry3Bb1 Bacillus thurintransgenic plants expressing Cry3Bb1 that would confer giensis (Bt) variant that is approximately eight times more lethal to protection to corn root tissue from larval feeding damcorn rootworm larvae than the wild-type protein. A DNA vector age. To further augment protection of the root system containing the modified cry3Bb1 gene was placed under control of a from larval feeding damage, modifications were introroot-enhanced promoter (4-AS1) and was introduced into embryonic duced in the cry3Bb1 gene that gave rise to an amino acid maize cells by microprojectile bombardment. Described here is the variant Cry3Bb1 protein with an eight-fold increase in molecular genetic characterization, protein expression levels, and field performance of the recently commercialized MON863 hybrids.

Biotechnological Prospects for Engineering Insect-Resistant Plants

“…A current commercial transgenic maize variety with resistance to corn rootworm, MON863, expresses a modified version of the Bt Cry3Bb1 toxin (Vaughn et al, 2005). Unmodified Cry3Bb1 is active against a number of coleopteran species, but toxicity toward Western corn rootworm was not sufficient to give adequate protection at levels of expression achievable in maize.…”

Modeling Evolution of <I>Diabrotica virgifera virgifera</I> (Coleoptera: Chrysomelidae) to Transgenic Corn With Two Insecticidal Traits

“…Initial efforts by industry have focused on registration of single events that express Bacillus thuringiensis Berliner proteins with insecticidal activity against the western corn rootworm (Moellenbeck et al 2001, Vaughn et al 2005, Walters et al 2008. However, in recent years, as more rootworm-protected traits have become available, the product development goal in corn has shifted beyond the single event per hybrid concept to one in which two separate rootworm-protected events are stacked together (pyramid) in the same hybrid.…”

Baseline Susceptibility of Western Corn Rootworm (Coleoptera: Crysomelidae) to Cry3Bb1 <I>Bacillus thuringiensis</I> Toxin

“…This event (referred to as MON 863) constitutively expresses the Cry3Bb1 toxin derived from Bacillus thuringiensis (Bt) in both root and above ground tissue, although only rootworm larvae are affected by the toxin (EPA 2003). This technology offers several important advantages over conventional rootworm management techniques, including reduced applicator exposure to insecticides and a narrower spectrum of activity, and it does not require special application equipment or calibration (Vaughn et al 2005). However, as with other transgenic Bt crops, the risk of resistance development is perceived as being high, especially for MON 863, which does not express a high dose of toxin such that signiÞcant survival and adult emergence from expressing plants have been reported (Vaughn et al 2005).…”