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Growth Stimulation of Armillaria mellea by Ethanol and other Alcohols in Relation to Phenol Concentration. Carroll P. Vance, Former Graduate Student, Department of Plant Pathology, The Ohio State University, Columbus 43210, Present address: Department of Botany, University of British Columbia, Vancouver 8; M. O. Garraway, Associate Professor, the Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 63:743-748. Accepted for publication 26 December 1972. DOI: 10.1094/Phyto-63-743.

The growth rate of 7-day-old Armillaria mellea thalli increased and the phenol concentration decreased on glucose media supplemented with various concentrations of ethanol. Similarly, the growth rate of thalli increased and the phenol concentration decreased when an ethanol supplement (500 µl/liter) was substituted by a comparable concentration of either propanol, butanol or isobutanol. Thus, the physiological responses of A. mellea to other low molecular weight alcohols, which promote mycelial growth and rhizomorph development, appear comparable to responses induced by ethanol. Extracts from 7-day-old thalli incubated for 48 hr on glucose media inhibited A. mellea mycelial growth and rhizomorph development. Comparable extracts from thalli incubated on glucose + ethanol (500 µl/liter) media were non-inhibitory. Extracts from thalli on glucose media contained two phenolic compounds, (detected by chromatographic separation on polyamide thin-layer plates) which were absent from extracts of thalli on glucose + ethanol media. One spot, at RF 0.17, revealed ultraviolet absorption maxima at 272 and 232 nm. The other, at RF 0.61, revealed one maximum at 270 nm. The presence of unique phenols in inhibitory extracts from thalli incubated on glucose media, and their absence from thalli incubated on glucose + ethanol media, suggests that ethanol promotes A. mellea thallus growth by altering the phenol composition in addition to reducing phenol concentration.