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Physiology and Biochemistry

Effects of Tannic Acid on Rhizomorph Production by Armillaria mellea. P. C. Cheo, Chief, Research Division, Los Angeles State and County Arboretum, 301 N. Baldwin Ave., Arcadia, CA 91006; Phytopathology 72:676-679. Accepted for publication 17 September 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-676.

On a defined basal medium, the fungus Armillaria mellea produced scanty mycelial growth with no rhizomorphs. When tannic acid (TA) was added to the medium, rhizomorph development as well as mycelial growth were strongly stimulated. Stimulation of mycelial growth was observed at 0.001% (w/v) TA. Stimulation of rhizomorph development, however, did not occur at TA concentrations less than 0.05%. The best production of rhizomorphs occurred at 0.3 to 1.0% TA. TA did not serve as a sole carbon source for the growth of A. mellea. The incorporation of TA in a basal medium, on the other hand, inhibited the growth of many other fungi. Fomitopsis annosa, a wood-rotting fungus, and Verticillim dahliae, a wilt-producing fungus, were strongly inhibited by TA. Gallic acid, as well as some other phenolic compounds, also stimulated to a lesser extent the development of rhizomorphs in A. mellea. This reaction to TA and other phenolic compounds may confer a competitive advantage in its parasitism.