Durable host-plant resistance, a desirable trait for integrated disease management
2001
Varma, A. and Mitter, N.
The intensification of agriculture and introduction of new cropping systems have resulted in a change in disease scenario in various parts of the world. The emergence of new and damaging diseases has posed a major challenge to scientists for their eco-friendly management to achieve full potential of crop yield so that increasing demands for food and feed can be met in the 21st century. In the past, plant diseases have been managed effectively by host-plant resistance. Some of these resistances have been very stable, whereas pathogens overcome others in a short time. It is therefore desirable to have durable host-plant resistance to minimize losses caused by plant diseases. Durability of resistance is a highly variable phenomenon. Recent developments in biotechnology have opened up new possibilities of incorporating durable resistance to pathogens in plants. For example, the introduction of both resistance and avirulence gene in plants could help in developing effective durable resistance in host plants. Transgenics for resistance to bacterial diseases are being produced. In viruses, genetically engineered resistance using coat protein, movement, and replicase genes is being exploited to produce resistant plants. Biotechnological approaches are also useful in marker-aided selection and RFLP mapping, identification of R genes, and gene pyramiding. Durability of the host against a pathogen cannot be predicted and can be seen only in retrospect. The strategy should be to manage resistance in such a way that the pathogen cannot overcome it. Recurrent selection of the host population against susceptibility and presumed major genes should be carried out. Pathologists and breeders should aim to achieve durable resistance in which the host plant is resistant in time and space.
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