Provenance variation for disease resistance in Pseudotsugamenziesii to the Swiss needle-cast pathogen, Phaeocryptopusgaeumannii

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Abstract
Nine provenances of Douglas-fir, Pseudotsugamenziesii, were examined for the presence of Swiss needle-cast pathogen, Phaeocryptopusgaeumannii, in a plantation at the University of British Columbia Research Forest, Haney, B.C. The provenances were represented in a randomized complete block design. A severe epidemic of Swiss needle cast had persisted in the plantation for a number of years. Fructification of the fungus on more than 75% of the foliage provided an opportunity to assess provenance variation in disease resistance. Analysis of variance demonstrated that there are significant differences among provenances in resistance, as indicated by needle retention, to the Swiss needle-cast pathogen. Linear regression indicated a positive relationship between needle loss and the proportion of the remaining needles with pseudothecia. Provenance variation for needle retention and fructifying needles both correlate strongly with rainfall data from the meteorological station nearest to each provenance origin. This result is consistent with the hypothesis that the provenances of Douglas-fir may have evolved in response to selection pressure imposed by the biological stress of Swiss needle-cast disease.