Ecology and resistance management forbacillus thuringiensistransgenic plants

Abstract

Transgenic plants expressing the endotoxin proteins of Bacillus thuringiensis (Bt) will be released for commercial production during this decade. While these plants have a great potential to reduce our dependence on pesticides for insect control, their success will be short-lived if insects rapidly develop resistance to the Bt toxins or if chemical use is needed to control other pests in the same production systems. Ecological studies can play a vital role in the design of strategies that avoid these problems by, for example, identifying key factors in insect life histories that influence the rate at which resistance evolves, validating management models that often make simple assumptions about the population biology of insects, identifying critical insect-plant interactions and determining whether pest control by transgenic plants is affected when the plants are stressed. These points can be illustrated from studies of non-transgenic ecosystems in the areas of host plant resistance, insecticide resistance management and the role of natural enemies in population regulation.

Improving Environmental Loading Assessments of Cry Protein from GM Plants Based on Experimentation in Cotton~!2008-09-12~!2008-11-15~!2008-12-05~!

“…Differences in transformation events and promoters could affect transgenic protein stability [25], however, all commercial cotton varieties derived their transgenic material from specific and stable insertion events MON531 [27] for Cry1Ac and MON15985 [10] for the Cry2Ab. This similarity in the inserted transgenic material suggests that variation in expression levels of Cry proteins is more likely to reflect differences between the parentage of tested lines, plant stress and/or the environmental conditions of the season [28]. Transcriptional regulation and temperature differences have been reported to effect Cry1Ac expression [7,29] and could affect Cry2Ab.…”

“…Whilst purified Cry2Ab has been reported as temperature stable in water [12], we observed instability of the Corn powder Cry2Ab standard when freeze/thawed. Onset of higher summer temperatures could also increase expression of heat shock proteins to the detriment of other proteins [28]. Whatever the reason for the decrease in Cry2Ab expression, it was common to both the assessed 289B and 289BR cultivars tested [6,23,30].…”

Relative Fitness of Cry1A-Resistant and -Susceptible <I>Helicoverpa armigera</I> (Lepidoptera: Noctuidae) on Conventional and Transgenic Cotton

“…armigera has a naturally higher tolerance to Cry1Ac (Liao et al 2002) than Heliothis virescens (F.) (Luttrell et al 1999), one of the target pests for transgenic cotton in the United States. This tolerance combined with attenuation in toxin expression over time (Fitt 1998) has resulted in complete larval development by H. armigera on Cry1Ac cotton in the Þeld (Fitt and Wilson 2000) and increases the likelihood that resistance will evolve in this species (Daly 1994). The capacity for H. armigera to develop resistance to Cry1Ac has been demonstrated in laboratory-selected strains from Australia (Akhurst et al 2003), China (Fan et al 2000), and India (Kranthi et al 2000).…”

Understanding and Manipulating Plant Attributes to Enhance Biological Control

“…Indirect effects of plant quality are receiving renewed attention with the use of genetically engineered, herbivore-resistant crops (Daly, 1994;Gould, 1994). In tobacco plants (N. tabacum), a moderate level of Bt endotoxin-mediated resistance was shown to enhance parasitism of Heliothis virescens F. larvae by the parasitoid Campoletis sonorensis (Cameron) (Johnson and Gould, 1992).…”