Substrate Hydrolysis Patterns of Post-Fire Ascomycetes (Pezizales)

Abstract

Forty-one isolates of post-fire Ascomycetes, representing 1 species of Sphaeriales and 25 species of Pezizales, were tested for ability to hydrolyze amylose, amylopectin, gelatin, xylan, lipid, pectin, chitin, cellulose, and lignin. Isolates were also assayed for the presence of phenol oxidase enzymes: laccase, tyrosinase and peroxidase. The majority of isolates were able to degrade amylose, amylopectin, gelatin, and xylan, and were unable to utilize chitin. Cellulose, lignin, and pectin utilization showed the least variation between isolates of the same species. Pectin hydrolysis and phenol oxidase production were strongly influenced by the pH of the medium. Phenol oxidase production was identified in both saprotrophs and biotrophs. However, lignin degradation was primarily observed in the saprotrophs. It is hypothesized that phenol oxidases in post-fire Pezizales function in lignin degradation in saprotrophs, but function primarily in detoxification of host-produced phenols in biotrophs. Tests were able to identify guilds of fungi associated with non-lignified substrates (e.g. litter, fine roots) and lignified substrates (e.g. wood, woody roots). Tests also helped distinguish between saprotrophic and biotrophic modes of nutrition. The majority of post-fire Pezizales appear to be opportunistic decomposers or facultative biotrophs adapted to the transient post-fire environment.