A Population Genetic Model of the Alternate Host System of Cronartium quercuum f. sp. fusiforme

By planting pines selected for resistance to fusiform rust, one might as a result select indirectly for more virulent rust strains. A simplified mathematical model was developed to describe the population genetics of the rust fungus, which is unusually complex because of the alternate host system. The mathematical model also formed the basis for a computer model, simulating the selection process. Five hypothetical situations were examined. If a gene for virulence was favored on the pine, but selectively neutral on the oak, it would become the predominant gene in the rust in about 20 years. If a gene for increased virulence would be selected for on the pine, but selected against on the oak, it would become the predominant gene in the rust in about 50 years. Forest Sci. 28:745-752.