Dynamics of bioluminescence by Armillaria gallica, A. mellea and A. tabescens

Although fungal bioluminescence is well documented, the ecological significance is poorly understood. We examined bioluminescence by three sympatric species of Armillaria wood decay fungi, differing in parasitic ability. Luminescence by mycelia of four genets of A. gallica, A. mellea and A. tabescens was examined in response to environmental illumination or mechanical disturbance. Luminescence dynamics were assessed in a time series of measurements every 2 min for 72 h for mycelia growing on malt agar or on Cornus florida root wood. Luminescence by the necrotrophic species A. gallica was enhanced by environmental illumination and mechanical disturbance of mycelia. In contrast luminescence by the more parasitic A. mellea and A. tabescens was quenched by prolonged exposure to environmental illumination and less responsive to mechanical disturbance. With environmental illumination absent, all mycelia representing six genets of each Armillaria species were constitutively luminescent. The temporal dynamics of luminescence by all mycelia were complex with no evidence of the previously reported diurnal periodicity. Differences among Armillaria spp. in bioluminescence expression might reflect differences in ecological context as well.