CELLULOSE-TRIGGERED SPORULATION IN THE GALACTOSE OXIDASE-PRODUCING FUNGUS CLADOBOTRYUM (DACTYLIUM) DENDROIDES NRRL-2903 AND ITS REIDENTIFICATION AS A SPECIES OF FUSARIUM

The production of extracellular galactose oxidase is limited to a few fungal species, including the important plant pathogens Fusarium grami nearum and F. moniliforme. The best-studied enzyme is the one produced by the mycoparasitic fungus Cladobotryum (Dactylium) dendroides NRRL 2903. The NRRL 2903 strain was first mis-identified as Polyporus circi natus and later re-determined as Dactylium dendroides, although sporul ation was never observed and the fungus was regarded as sterile. Upon growth at 25-degrees-C, 50 rpm, in liquid medium containing 2% cellulo se as the sole carbon source, and in the presence of 0.5-0.75% yeast e xtract, conidial production was induced in NRRL 2903, which was re-ide ntified as Fusarium sp. The only other known commercial strain of Clad obotryum (Dactylium) dendroides able to produce galactose oxidase, ATC C 46032, also produced fusiform conidia upon growth in cellulose-conta ining medium, and was shown to be genetically identical to the NRRL 29 03 strain. Genetic comparison with six different representative strain s of Cladobotryum dendroides (teleomorph: Hypomyces rosellus), and fou r strains of the closely related Hypomyces aurantius, based on the ana lysis of the presence or absence of a homologous galactose oxidase gen e (gaoA), RAPD-PCR and RFLP analysis, confirm the distinct nature of t he NRRL 2903 strain and Cladobotryum dendroides. Despite the resemblan ce of NRRL 2903 conidia and conidiophores to those of Fusarium chlamyd osporum genetic comparison, with three different strains, suggests NRR L 2903 cannot be re-identified as F. chlamydosporum. Two of the strain s, however, contain a region in their genome that is highly homologous to the galactose oxidase gene (gaoA), and one strain exhibits extrace llular galactose oxidase activity but only partial homology to the gao A gene of NRRL 2903.