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Letter to the Editor

Comments on the van der Kamp-Tait Susceptibility Model for Resistance Selection. F. G. Peet and R. S. Hunt. Pacific Forestry Centre, Canadian Forestry Service, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5. Phytopathology 85:1332-1334. Accepted for publication 22 August 1995. Copyright 1995 by Natural Resources Canada, Government of Canada. doi:10.1094/Phyto-85-1332.

van der Kamp and Tait (3) developed a mathematical model to describe the lodgepole pine (Pinus contorta Douglas ex Loud.)-western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) pathosystem. Although discussed in terms of this particular disease, the model concerns itself with the segregation of members of a natural population that are susceptible and resistant to diseases characterized by discrete infections. van der Kamp (2) applied the model to investigate the theoretical limits of selecting trees for resistance to a particular disease and concluded that "...the ability to identify resistant trees is significantly compromised by random placement of spores and by the large number of trees that remain uninfected". In contrast, our examination of the model predicts increased levels of resistance when disease-free trees are selected.