Host responses in the xylem of trees after inoculation with six wood-decay fungi differing in invasivenessThis article is one of a collection of papers based on a presentation from the Stem and Shoot Fungal Pathogens and Parasitic Plants: the Values of Biological Diversity session of the XXII International Union of Forestry Research Organization World Congress meeting held in Brisbane, Queensland,

Abstract

Host responses, i.e., formation of reaction and barrier zones, were studied in the xylem of Douglas-fir, beech, oak, and sycamore trees, after wounding and artificial inoculation with brown-, soft-, and white-rot fungi. The objective of this study was to determine whether strongly invasive wood-decay fungi trigger a higher magnitude of host response than weakly invasive fungi. Differences in active host response, observed microscopically, depended on wood anatomy. Restriction of discoloration and decay by reaction zones was primarily influenced by the content and distribution of parenchyma cells within the sapwood of each host. By contrast, barrier-zone anatomy showed similarities to the basic xylem structure of each host, except for some cell types that were either reduced in number or absent. Regardless of the decay fungus inoculated, individual trees of each host responded differently. With the exception of beech trees inoculated with the soft-rot fungus Kretzschmaria deusta (Hoffm.: Fr.) P. Martin and the white-rot fungus Trametes versicolor (L.: Fries) Pilát, host response appeared to be nonspecific, as the degree of fungal invasiveness did not influence the magnitude of host response within the xylem of investigated trees.