Abstract
Genetically modified (GM) legumes expressing the α-amylase inhibitor 1 (αAI-1) from Phaseolus vulgaris L. or cysteine protease inhibitors are resistant to several bruchid pests (Coleoptera: Chrysomelidae). In addition, the combination of plant resistance factors together with hymenopteran parasitoids can substantially increase the bruchid control provided by the resistance alone. If the strategy of combining a bruchid-resistant GM legume and biological control is to be effective, the insecticidal trait must not adversely affect bruchid antagonists. The environmental risk assessment of such GM legumes includes the characterization of the targeted enzymes in the beneficial species and the assessment of the in vitro susceptibility to the resistance factor. The digestive physiology of bruchid parasitoids remain relatively unknown, and their susceptibility to αAI-1 has never been investigated. We have detected α-amylase and serine protease activities in all five bruchid parasitoid species tested. Thus, the deployment of GM legumes expressing cysteine protease inhibitors to control bruchids should be compatible with the use of parasitoids. In vitro inhibition studies showed that sensitivity of α-amylase activity to αAI-1 in the parasitoids was comparable to that in the target species. Direct feeding assays revealed that harmful effects of α-amylase inhibitors on bruchid parasitoids cannot be discounted and need further evaluation.
Highlights
Grain legumes, known as pulses or food legumes, are mainly cultivated in developing countries, where they are essential for nutrition
Characterization of a-amylase Activity We analyzed the optimum pH, the specific activity, and the effect of two specific a-amylase inhibitors on the hydrolysis of potato starch to characterize a-amylase activity in several bruchid and hymenopteran parasitoids (Table 1). a-Amylase activity was detected over a broad range of pH in both bruchids and parasitoids
In vitro inhibition studies were conducted to assess the susceptibility of bruchids and parasitoids to purified amylase inhibitor 1 (aAI-1). aAmylase activity in extracts from all parasitoid larvae and females was reduced by the inhibitor (Fig. 1B–F)
Summary
Known as pulses or food legumes, are mainly cultivated in developing countries, where they are essential for nutrition. Pulses represent a source of income and livestock feed and meet the requirements of small-scale, low-income farmers in developing countries [1]. Several coleopteran and lepidopteran pests are responsible for extensive losses to stored grain legumes because these pests develop and reproduce rapidly, completing multiple generations in the storage. Insect pests increase the temperature and humidity of the stored pulses, which increases grain respiration and thereby reduces grain quantity and quality [3]. The average grain-weight loss for pulses due to insect pests is 20% [4], it can be up to 100% and is generally much higher than the loss caused by rodents, microorganisms, and other pests [2]. Larvae of several Acanthoscelides, Zabrotes, and Callosobruchus spp. (Coleoptera: Chrysomelidae) are among the most important insect pests of pulses worldwide
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