Isozyme subgroups in Trichoderma section Longibrachiatum

Abstract

Seventy-eight representatives of Trichoderma sect. Longibrachiatum, Hypocrea jecorina, and H. schweinitzii were compared using ten enzyme systems. The results essentially supported Bissett's morphologically based taxonomy of Trichoderma sect. Longibrachiatum, in that the species T. longibrachiatum, T. citrinoviride, T. parceramosum, and T. pseudokoningii could be distinguished. Trichoderma reesei was closely related to H. jecorina and more distantly linked to T. longibrachiatum, thus the synonymy of T. reesei with T. longibrachiatum was not supported. The possibility that T. reesei is a clonal derivative of H. jecorina is discussed. Strains of Trichoderma citrinoviride were intermingled with Northern Hemisphere strains of H. schweinitzii, suggesting it is the anamorph of that holomorph. Trichoderma pseudokoningii, the type of which was originally derived from ascospores of an Australian collection of H. schweinitzii, clustered with some New Zealand collections of H. schweinitzii, but independently of Northern Hemisphere H. schweinitzii. Trichoderma pseudokoningii may be rare outside of Australasia. No teleomorph could be linked either to T. longibrachiatum or T. parceramosum. Four collections of H. schweinitzii from New Zealand (3) and the Andean region of Venezuela formed a discrete group within the cluster that included H. jecorina and H. schweinitzii. There was great homogeneity among strains of H. jecorina from a narrow equatorial band, suggesting continuing gene flow over disjunct regions.

Key Words:

• Hypocrea
• Hypocreales
• systematics