Strategies for Molecular Resistance Breeding (& Transgenic Plants)

Despite the enormous input over the years in the development of control measures, diseases caused by fungi are still a major problem in agriculture. The epidemic spread of those diseases is controlled by a) agricultural management techniques, such as crop rotation and avoiding the spread of infested soil and diseased plant materials, b) the breeding of specific resistance traits into crops and c) the application of chemical compounds. Although breeders have successfully produced cultivars of crops resistant against specific fungal diseases, they are confronted continually with the evolvement of new races of fungal pathogens imposing new problems. Therefore, farmers still rely on the use of agrochemicals. However, the use of chemicals is costly and potentially damaging to the environment, and over time they become less efficient due to adaptation of the pathogen. High production costs together with a growing public concern about the environment have stimulated research into new alternatives in crop protection. One such an alternative is biological control, another the application of gene transfer techniques. During recent years a number of strategies to control fungal diseases with transgenic plants has been proposed. These strategies include the expression of genes encoding proteins able to inhibit growth of fungi, the fungus-inducible production of compounds toxic to either the invading fungus or plant cells, the production of inhibitors of fungal enzymes and others (reviewed by Lamb et al., 1992; Cornelissen and Melchers, 1993). New approaches are still emerging.