Genetic engineering to improve biotic stress tolerance in plants

Abstract

Genetic engineering of plants for resistance is an effective method to counter pathogens and pests owing to the specificity and efficiency of the technology. The genes that have been used to genetically engineer resistance are as diverse as the diseases they act against. In cases where gene-for-gene resistance coded by resistance (R) genes exists, engineering resistance in plants becomes a straight path. Different classes of R genes have been engineered to provide resistance against viruses, bacteria, filamentous phytopathogens, and nematodes. Where the resistance mechanism is not R gene mediated, myriad of other mechanisms have been tried. These include the use of genes coding for antimicrobial compounds against bacterial and filamentous pathogens. The cloning of transcription factors, receptor genes, proteases, and genes involved in the systemic acquired resistance (SAR) has also been found to be effective. RNA silencing against specific genes involved in pathogenicity has proved to be an efficacious strategy against viruses and nematodes. Posttranscriptional silencing of genes coding for viral coat proteins has been successful, both scientifically and commercially. The most extensively used technology till date has been the introduction of cry genes from the bacterium Bacillus thuringiensis into plants to render them resistant against insect pests. Advances in molecular biology have paved the way for new strategies, the phenomenon of host-induced gene silencing (HIGS) being an interesting example. Amidst all the hue and cry raised against genetic modification of crops, it is necessary to highlight the scientific principles involved so as to make full use of a technology that could very well solve the problem of food shortage.