Variation in susceptibility to sweet fern rust among <i>Pinus</i><i>contorta</i> and <i>P</i>. <i>banksiana</i>

Abstract

Cronartiumcomptoniae incidence was measured on 62 provenances of Pinusbanksiana and 77 provenances of P. contorta. Infection incidence varied among provenances in both hosts. Pinusbanksiana provenances beyond the geographic range of Comptoniaperegrina, and P. contorta provenances beyond the geographic range of Myricagale, were more susceptible than some provenances within the range of these alternate hosts. It is hypothesized that selection pressure is important in maintaining resistance to C. comptoniae.