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Abstract
Variation within the internal transcribed spacer (ITS-1 and ITS-2) regions of ribosomal DNA of 103 strains was studied to examine relationships within Trichoderma sect. Longibrachiatum and related teleomorphs, Hypocrea schweinitzii and H. jecorina. The four species, T. longibrachiatum, T. pseudokoningii, T. parceramosum and T. citrinoviride, that were originally assigned by morphological criteria to this section were recognized by sequence analysis. Trichoderma reesei, which was previously considered to be synonymous with T. longibrachiatum, and T. saturnisporum which was placed originally in sect. Saturnisporum because of its warted conidia, are assigned to the section. ITS sequences of T. ghanense, originally assigned to sect. Saturnisporum, could not be distinguished from the sequence of T. parceramosum, indicating that the two may be synonymous. Trichoderma “todica”, an unpublished name based on the antiviral strain NRRL 3091, is T. parceramosum. Interspecific variability within sect. Longibrachiatum was low (2.2-4.8% in ITS-1, 0–10.2% in ITS-2) when compared with species of other sections. Phylogenetic analysis showed strong support for the monophyly of sect. Longibrachiatum. The Hypocrea teleomorphs with anamorphs that could be assigned to sect. Longibrachiatum fall into at least 6 in part geographically defined groups on the basis of ITS sequences. The anamorphs of three of these groups can be assigned to T. longibrachiatum, T. citrinoviride, and T. pseudokoningii, respectively. Variability among these teleomorph groups is in the same order of magnitude as among the six anamorph species of sect. Longibrachiatum. Hypocrea jecorina and T. reesei showed 100% sequence homology. Classification derived from ITS sequences is discussed in comparison with results from other molecular methods.
