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Physiology and Biochemistry

Chemical Constituents in Root Bark of Five Species of Western Conifer Saplings and Infection by Armillaria ostoyae. J. A. Entry, Research associate, Department of Forest Science, Oregon State University, Corvallis, 97331-5705; N. E. Martin(2), R. G. Kelsey(3), and K. Cromack, Jr.(4). (2)Scientist, U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, 1220 S. Main, Moscow, ID 83843; (3)Research scientist, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 3200 Jefferson Way, Corvallis, OR 97331; (4)Associate professor, Department of Forest Science, Oregon State University, Corvallis, 97331-5705. Phytopathology 82:393-397. Accepted for publication 16 December 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-393.

Ten years after being planted, five species of western conifer saplings were inoculated with two isolates of Armillaria ostoyae. Infection ratings assigned to A. ostoyae were highest in saplings of Abies grandis and Pseudotsuga menziesii and lowest in those of Larix occidentalis. Height and diameter growth were greater in saplings of L. occidentalis, Pinus monticola, and Pinus ponderosa than in those of A. grandis and P. menziesii. Concentrations of sugar and starch in root bark were higher in A. grandis and P. menziesii than in the other species. Concentrations of phenolics and protein-precipitable tannins were highest in root bark of L. occidentalis. Biochemical parameters of root bark were regressed with assigned ratings of infection by A. ostoyae; coefficients of determination (r²) ranged from 0.06 (cellulose) to 0.56 (sugars). Ratios of the energetic costs of phenolic and lignin degradation relative to the energy available from sugars (E_pd:E_as and E_ld:E_as) were correlated with infection rate (r² = 0.87 and 0.76, respectively). Species that are more susceptible to infection by A. ostoyae may produce lower concentrations of phenolics and more sugar in root bark, thereby increasing the energy available to the fungus to degrade the phenolics and invade the host trees.