Variation in Susceptibility of Noctuid (Lepidoptera) Larvae Attacking Cotton and Soybean to Purified Endotoxin Proteins and Commercial Formulations of Bacillus thuringiensis
Authors: Luttrell, R. G.; Wan, L.; Knighten, K.
Source: Journal of Economic Entomology, Volume 92, Number 1, February 1999 , pp. 21-32(12)
Publisher: Entomological Society of America
Abstract:Susceptibility of Heliothis virescens (F.), Helicoverpa zea (Boddie), Pseudoplusia includens (Walker), Spodoptera exigua (Hübner), and Spodoptera frugiperda (J. E. Smith) to purified endotoxins and commercial formulations of Bacillus thuringiensis Berliner was measured in a wide range of colonies collected from 8 states in the U.S. Cotton Belt during 1992 and 1993. Results indicated that field-collected colonies of H. virescens, H. zea, P. includens, and S. frugiperda were as susceptible as laboratory-reared colonies and those reported in the literature to the purified endotoxin proteins Cry1Ac and Cry1Ab or the commercial formulations Javelin WG, Dipel ES, and Condor OF in diet-treated assays. Colonies of S. exigua collected from transgenic cotton expressing endotoxin protein had elevated median lethal concentrations (LC50s) compared with a colony collected from nontransgenic cotton or those from laboratory colonies. Ranges of LC50s for field-collected colonies of H. virescens generally were similar to the ranges observed for laboratory colonies and similar to those reported in the literature. Wider ranges of variation in LC50s were observed among populations of H. zea and S. exigua than among populations of the other species. However, the highest LC50 observed for H. zea was no higher than those reported in the literature. Only a few colonies of P. includens and S. exigua were tested. P. includens susceptibility was generally greater than that of H. virescens and less than that of H. zea. S. frugiperda was the least susceptible species studied. Variability in LC50s obtained with Cry1Ac (r = 0.702) correlated with variability in LC50s for Cry1Ab across 13 colonies of H. virescens exposed to both proteins. Colonies of H. zea and H. virescens were pooled into single colonies and selected with the insecticidal proteins to produce endotoxin-resistant strains. Selection for resistance in H. virescens was not successful, but a strain of H. zea was selected that had elevated LC50s (10 times) after 2 generations and very high LC50s compared with a susceptible laboratory strain (100 times) after 8 generations, suggesting that H. zea has the genetic capacity to develop resistance to endotoxin proteins.
Document Type: Research Article
Publication date: February 1, 1999
- Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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