Genetic Transformation of Crops for Insect Resistance: Potential and Limitations

Abstract

Transgenic resistance to insects has been demonstrated in plants expressing insecticidal genes such as δ-endotoxins from Bacillus thuringiensis (Bt), protease inhibitors, enzymes, secondary plant metabolites, and plant lectins. While transgenic plants with introduced Bt genes have been deployed in several crops on a global scale, the alternative genes have received considerably less attention. The protease inhibitor and lectin genes largely affect insect growth and development and, in most instances, do not result in insect mortality. The effective concentrations of these proteins are much greater than the Bt toxin proteins. Therefore, the potential of some of the alternative genes can only be realized by deploying them in combination with conventional host plant resistance and Bt genes. Genes conferring resistance to insects can also be deployed as multilines or synthetic varieties. Initial indications from deployment of transgenics with insect resistance in diverse cropping systems in USA, Africa suggest that single transgene products in standard cultivar backgrounds are not a recipe for sustainable pest management. Instead, a much more complex approach may be needed, one which may involve deployment of a combination of different transgenes in different backgrounds. Under diverse climatic conditions and cropping systems of tropics, the success in the utilization of transgenics for pest management may involve decentralized national breeding programs and several small-scale seed companies. While several transgenic crops with insecticidal genes have been introduced in the temperate regions, very little has been done to use this technology for improving crop productivity in the harsh environments of the tropics, where the need for increasing food production is most urgent. There is a need to develop appropriate strategies for deployment of transgenics for pest management, keeping in view the pest spectrum involved, and the effects on nontarget organisms in the ecosystem.

Deterrent activity of plant lectins on cowpea weevil Callosobruchus maculatus (F.) oviposition

“…Most probably, the obvious differences in toxicity are somehow related to the fact that plant lectins are a complex composite of multiple families of evolutionary related proteins with markedly different biochemical and physicochemical properties, carbohydrate-binding specificity and biological activities (Van Damme et al, 1998a,b). During the last two decades numerous reports were published on the insecticidal activity of plant lectins against many insect pests belonging to the orders of Lepidoptera, Coleoptera, Diptera and Homoptera (Boulter et al, 1990;Gatehouse et al, 1995;Hilder et al, 1995;Sharma et al, 2004). Interestingly, some of these reports provided evidence for a moderate to strong inhibition for dietary lectins on larval development of C. maculatus (Murdock et al, 1990;Oliveira et al, 1999;Omitogun et al, 1999;Machuka et al, 2000;Zhu-Salzman et al, 2003;Sharma et al, 2004).…”

Genetic Engineering in Conifer Plantation Forestry

“…Genetic engineering has been used commercially for over a decade, to produce agricultural plants resistant to herbicides (MAZUR and FALCO, 1989), insects (SHARMA et al, 2004), adverse environmental conditions (WANG et al, 2003), and with improved nutritional or medicinal value (SAUTTER et al, 2006). These modern biotechnologies have contributed to gains in productivity and quality of agricultural crops (CARDOZA and STEWART, 2004) and farmers have taken up improved varieties at unprecedented speed.…”

Anti-insect potential of a lectin from the tuber, Dioscorea mangenotiana towards Eldana saccharina (Lepidoptera: Pyralidae)

“…Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License anti-insect and anti-microbial, has been proposed on the basis of indirect and direct evidence (Sharma et al, 2004;Wong et al, 2010;Roy et al, 2014;Al Atalah et al, 2014). Thus, there is intensified research on the use of lectins in protecting crop plants from the attack of insects and fungal pathogens.…”

“…The anti-insect activity of plant lectins can thus have great economic potential in pest management because lectins being primary metabolic products, their genes can be good candidates to confer insect resistance to transgenic crops (Sharma et al, 2004). Therefore, the purification and characterization of lectins from new sources may reveal genes with the potential to be used in the genetic improvement of crops.…”