Tropical Soil Fungi

SUMMARY

Thirty-one samples were collected from varied soils in Panama and Costa Rica. Because of diversified soil sampling from Barro Colorado Island, many of the more common fungi were isolated. This would be less true of other areas due to fewer collections.

Several media were selected on the basis of a screening process which proved favorable for isolation of soil fungi. IIa-rose bengal-streptomycin agar, hemp agar, non-carbon solution agar with amino acids or growth substances (biotin, thiamin), plain agar and dahlia-dextrose agar were the ones most suitable if using direct inoculation of soil. Addition of dried corn stalks, Desmodium twigs or Phleum tissue stimulated growth.

One hundred and thirty-five species were isolated, of which 100 were Fungi Imperfecti. More Ascomycetes were recorded than Phycomycetes.

Nine genera are listed as the most common in the soil samples studied. Species of Aspergillus and Chaetomium seem to have a wide distribution in this tropical region, whereas Mucor and Rhizopus were rarely recorded.

The direct inoculation method was practicable if weak media were used. Growth of most fungi was restricted, but not inhibited, on such substrates.