Mycorrhizal and pathological associations of dematiaceous fungi in roots of 7-month-old tree seedlings

Abstract

Colonizing behaviors of five dematiaceous fungi that variously form ectomycorrhizal, ectendomycorrhizal, or pseudomycorrhizal associations with roots were studied at pH 3.0 and 5.7. Species selected were five Hyphomycetes, viz., the three new species Phialophorafinlandia, Chloridiumpaucisporum, and Phialocephalafortinii; the well-known Phialocephaladimorphospora; and Cenococcumgeophilum. Control seedlings and those inoculated with C. paucisporum, P. fortinii, and C. geophilum were badly stunted and showed little growth at pH 3, whereas moderate growth of roots and seedlings was exhibited by ectendomycorrhizal P. finlandia and pathogenic P. dimorphospora. At pH 5.7, P. fortinii seedlings were mostly dead and those with P. dimorphospora were more sparsely developed than at pH 3. The controls as well as the remaining fungal associations were healthy at pH 5.7. Phialophorafinlandia and C. paucisporum associations were ectendomycorrhizal but C. geophilum associations were ectomycorrhizal. The nature of the mycorrhizal association, whether ecto- or ectendo-mycorrhizal, was largely controlled by the host. Structures such as sclerotia were determined by the fungus. Anatomical features of the various associations are shown in accompanying photographs.