Importance of R-genes
Conventionally the genes related to the resistance response against pathogens are defined resistance genes (Nurnberger and Lipka, 2005).
Plant resistance genes family is one of the most studied not only for its scientific importance but also for the great impact that discoveries in this field can have for humans. The plant breeding for resistance to biotic stresses is still a top priority because of the heavy losses that plagues each year causes to world agriculture. The mean losses of all crops amount to nearly half of the potential output, and about 30% of these is due to pests and diseases caused by fungi, viruses, and bacteria.
The chemical control still remains the most widely used strategy, despite its total ineffectiveness against some pathogens (viruses, viroids, and mycoplasma) and its enormous economic and environmental impact. The plant breeding based on the use of resistant varieties, however, appears to be an ideal method, to eliminate or reduce the need for chemicals during cultivation, while simultaneously decreasing their environmental impact. In that sense, improving our knowledge of the plant immune system is crucial.
Despite the importance of this issue and dedication of many researchers, the studies in this field proceed slowly because of the complexity of the interaction between plants and pathogens and the establishment of the disease.