The effects of host genotype, growth rate, and needle age on the distribution of a mutualistic, endophytic fungus in Douglas-fir plantations

Abstract

Two young plantations of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were examined for the presence of a symptomless endophytic fungus, Meriaparkeri Sherwood-Pike (Hemiphacideaceae). This fungus occurred in the needles of nearly every tree examined, with infection frequencies increasing with the age of the needle. Previous reports have asserted that M. parkeri is a mutualist that produces insecticidal toxins. The maternal parentage of the trees and age of the needles were highly significant predictors of infection frequencies. A detailed examination of two families of trees revealed that infection frequencies differed between sites and were positively correlated with the height of the host. Mutualism and microhabitat effects are discussed.