Special Section: Transgenic Crops

AFTER centuries of improving crop plants by breeding for desirable traits, agricultural scientists are now using the tools of molecular biology and genetic engineering to develop transgenic plants with the desired genes. Enormous progress has been made over the past decade in our understanding of the highly complex molecular events that occur in plant–pathogen interactions. This knowledge in turn has provided a number of options and strategies which can be and have been used to make transgenic plants resistant to pathogens. This review deals with fungal pathogens of crop plants. Starting from the first step of mutual recognition of host and pathogen which involves resistance gene–avirulence gene interaction , moving onto immediate response of the plant in terms of hypersensitive response, production of active oxygen species, followed by local resistance response in terms of production of pathogenesis-related proteins and other antifungal proteins, then to the final step of syste-mic acquired resistance (SAR), all this information has been/or is being used to produce fungus-resistant trans-genic plants in different crop species. In this review we discuss strategies that have been used to produce fungus-resistant transgenic plants and also discuss some of the emerging possibilities in the wake of large scale genome sequencing projects being undertaken in crop plants. Significant yield losses due to fungal attacks occur in most of the agricultural and horticultural species. In Indian context, fungal diseases are rated either the most important or second most important factor contributing to yield losses in our major cereal, pulse and oilseed crops. On the basis of a recent survey 1 , contribution of fungal diseases towards total yield loss in some important crops in India has been summarized in Table 1. Incidence of plant diseases has been controlled by agronomic practices that include crop rotation and use of agrochemicals and by breeding new strains and varieties that contain new resistance conferring genes. The use of agrochemicals poses many dangers that include harmful effects on the ecosystem and an increase in the input cost of the farmers. The breeding of resistant crops is time consuming and has to be a continuous process as often new races of pathogens evolve and crops become susceptible. Despite the boom and bust cycles, breeders have been successful in protecting some of the major crops grown around the world from fungal diseases. A major success story is wheat in which systematic breeding has been done to develop varieties …