Pectinolytic activity and isozymes in European Armillaria species

Abstract

Pectinolytic activities in Armillaria ostoyae, Armillaria mellea, Armillaria gallica, Armillaria borealis, and Armillaria cepistipes were assessed by measuring the ability of fungal strains to reduce the viscosity of their pectic growth media. Isozyme patterns of pectin esterases and polygalacturonases were determined directly from the culture filtrate. A total of 94 strains, representing isolations from various parts of Europe, were analyzed for their isozyme patterns. Armillaria mellea and A. borealis caused a 50% reduction in viscosity within 7 and 9 days, respectively. Growth medium from the other species were slower to reach the 50% level, i.e., means were 13 days for A. ostoyae and 17 days for A. cepistipes and A. gallica. All species produced more isozymes on spruce wood than on citrus pectin medium, and pectic isozyme patterns differed between media. The pectic isozyme pattern for A. mellea differed distinctly from those of the other four species by having two bands of polygalacturonase not found in the others. The pectic isozyme patterns of the other four species were separated using multivariate analysis. The value of such analyses for use in distinguishing between European Armillaria species is discussed, as is the relation between enzyme activity and fungal pathogenicity. Key words: root rot, diagnostic tests, Agaricales, polygalacturonase, pectin esterase.