CHITINOLYTIC ENZYMES OF PATHOGENIC AND ECTOMYCORRHIZAL FUNGI

Four ectomycorrhizal basidiomycetes (Boletinus cavipes, Paxillus involutus, Suillus variegatus and Pisolithus tinctoritus), two pathogenic root-infecting basidiomycetes (Heterobasidion annosum and Armillaria ostoyae) and the oomycete Phytophthora cinnamomi were screened for chitinolytic activity in liquid culture. N-Acetylglucosaminidase, exo- and endo-chitinase activity were distinguished using fluorogenic 4-methylumbelliferyl substrates. N-Acetylglucosaminidase was the predominant enzyme activity recorded: exochitinase was the predominant chitinase. The pathogenic basidiomycetes had higher specific activities against all substrates than the ectomycorrhizal fungi. There was considerable variation in activity between the ectomycorrhizal isolates. P. cinnamomi showed N-acetylglucosaminidase activity only. In general, chitinolytic activities were highest when chitin was present in the growth medium and were repressed in the presence of glucose. Diammonium phosphate did not repress chitinolytic activities.