Organically grown products are more labor intensive requiring a mixture of different plants and the use of natural predators to control pests. The increased labor, controls, and planting techniques lead to smaller yields than conventional farming methods and therefore an increased price at market. Yet the quest for better health and cleaner living hasn't stalled the market for organic products. Another option is the use of naturally resistant strains of plants. One of the most active and rapidly breaking areas in plant pathology is the molecular basis for disease resistance, in essence how genes and gene products interact with those of the host.
Virulence is a measure of the ability of strains of a species to cause disease.
The pathogen caries the dominant Avr gene for avirulence. The plant that caries a dominant R gene codes for receptors that have a specificity for a dominant Avr gene product of the pathogen. In real life multiple R genes can occur at different loci. As the numbers increase so does the complexity. This same concept can be applied to the pathogen.