Antagonistic Activity of Pseudohalonectria and Ophioceras

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Abstract
In vitro antagonistic activity of species of two closely related freshwater, lignicolous, ascomycete genera, Pseudohalonectria and Ophioceras, was studied. Species were tested in paired cultures on agar against representatives of a wide array of fungal taxa. Percent inhibition was measured and species were ranked according to their ability to inhibit and to resist inhibition. Species in all fungal taxa tested were inhibited to some extent by all species of Pseudohalonectria. Growth of most species of filamentous fungi tested was strongly inhibited at a distance by species of Pseudohalonectria. Species of Ophioceras were generally less inhibitory, especially at a distance. Stimulation of growth of Pseudohalonectria species was observed in some interactions. Growth of a yeast, Saccharomyces cerevisiae, and two bacteria, Escherichia coli and Bacillus subtilis, were unaffected by species in both genera. Spore germination of Cylindrocarpon ianthothele was not greatly inhibited by species of Pseudohalonectria or Ophioceras, while germ tube elongation was inhibited by Pseudohalonectria species. Culture filtrates of P. longirostrum were inhibitory to Pachysolen tannophilus, a yeast used as a bioassay organism.