Effects of Hydrolyzable Tannins on In Vitro Growth of Armillaria calvescens and A. gallica

Abstract

We hypothesized that Armillaria gallica, which is abundant in oak-dominated forests, is more successful at oxidizing and metabolizing polyphenols than A. calvescens, which is mostly restricted to maple-dominated forests. Isolates were challenged with up to seven concentrations of tannic acid (TA), gallic acid (GA), and black oak root bark extracts (RBE). Six concentrations of glucose and ethanol were also tested to determine the influence of available carbon on growth. Colony area and biomass values were analyzed using a GLM and Tukey's HSD test. When challenged with 0.12% concentrations of TA, GA, and RBE, A. gallica produced a significantly larger biomass in all treatments and larger colony areas in four of the five treatments compared to control values. A. gallica also produced a significantly larger number of rhizomorphs than A. calvescens on RBE medium. In contrast, A. calvescens generated significantly larger biomass over control treatments only when RBE was added, and values were substantially less compared to A. gallica. Growth of both species was significantly greater when ethanol was added, especially on GA medium, while glucose had little effect. Results from this study suggest that A. gallica is better at oxidizing and metabolizing polyphenols than A. calvescens.