Frank, S. A. 1992. Models of plant-pathogen coevolution. Trends in Genetics 8:213-219.

Plant populations are often genetically polymorphic for resistance to pathogens. The effectiveness of this resistance is limited because the pathogens are, in turn, polymorphic for virulence genes that can escape plant resistance. Theoretical models combined with intriguing preliminary data suggest that these plant-pathogen polymorphisms are maintained by endless cycles of coevolution within populations combined with occasional immigration of new virulence and resistance genes from distant populations.