Cultural characterization and chlamydospore function of the Ganodermataceae present in the eastern United States

The cultural characteristics of fungi can provide useful information for studying the biology and ecology of a group of closely related species, but these features are often overlooked in the order Polyporales. Optimal temperature and growth rate data can also be of utility for strain selection of cultivated fungi such as reishi (i.e., laccate Ganoderma species) and potential novel management tactics (e.g., solarization) for butt rot diseases caused by Ganoderma species. Historically, the taxonomy of the laccate (shiny) Ganoderma species has been unresolved and many species have been treated together as G. lucidum. The cultural characteristics of Ganoderma species from the United States are needed to understand the biology of these unique species that have all been lumped under this name. Culture morphology, average growth rate, optimal temperatures, and resiliency to elevated temperature exposure were characterized for isolates of Ganodermataceae taxa from the eastern United States, including Ganoderma curtisii, G. martinicense, G. meredithiae, G. ravenelii, G. sessile, G. tsugae, G. tuberculosum, G. cf. weberianum, G. zonatum, and Tomophagus colossus. We documented differences in linear growth rates and optimal temperatures between taxa. Isolates of G. sessile and T. colossus grew the fastest, and isolates of G. meredithiae, G. ravenelii, and G. tsugae grew the slowest. Isolates of G. sessile, G. martinicense, G. cf. weberianum, and T. colossus constitutively produced chlamydospores on malt extract agar, and these species were the only species to survive long-term exposure (30 or 40 d) to 40 C. We hypothesize that chlamydospores function as survival structures that serve as propagules resilient to adverse temperature conditions, especially heat. Cultural characteristics of G. martinicense, G. ravenelii, G. tuberculosum, and G. cf. weberianum collected from the United States are described for the first time.