Contribution of durable disease resistance to sustainable agriculture

Durable disease resistance and sustainable agriculture are two important concepts that have not been defined well enough for many people to determine with certainty whether a particular entity fits into either category. While there is not agreement on either definition, there is little disagreement that each concept is a desirable objective. Ironically, both concepts can be reduced to `over a long period of time'. While most people would not argue with the indefinite characterization of either concept, disagreement quickly arises when consideration begins of how to achieve either. Most disease resistance that is rendered ineffective is race specific. The pathogen population is shifted genetically to defeat the resistance gene. When resistance is only partial, the population shifts are less likely to occur. Equally so, the more complex the genetics of the resistance, the more difficult it is for the pathogen to evolve to a form that can overcome the resistance. Throughout history, there are countless examples of major losses of crops when previous effective resistance has been rendered ineffective, causing severe hardship and even devastating famines, e.g., Irish potato famine. Fortunately, there are also examples of resistance that has given protection over an extended time, one is rust in maize. Ultimately, adding genetic complexity to many host plant resistances is likely to extend their effectiveness (greater durability). Similarly, adding biodiversity to the landscape for both plants and animals is likely to increase the resiliency of the ecosystem involved. In both cases, the derived food system will be more secure.