Author
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Samuels, Gary |
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Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/11/2005 Publication Date: 1/2/2006 Citation: Samuels, G.J. 2005. Changes in taxonomy, occurrence of the sexual stage and ecology of trichoderma spp. Phytopathology. 96:195-206 Interpretive Summary: Fungi in the mold genus Trichoderma are useful in the biological control of plant diseases. Development of effective methods to control diseases using these fungal biological agents is hindered by inadequately defined and characterized species. In this paper the history and progress about the characterization, naming, biology and ecology of Trichoderma and their sexual state Hypocrea are reviewed. The definition and characterization of species of Trichoderma in a modern sense are discussed based on the discovery of their sexual states. The Hypocrea sexual states are often difficult to determine because the Trichoderma asexual state looks so different from the sexual state. Molecular data were used to determine that these two states are actually the same species and to define each species. A table is presented of standard DNA sequences, a portion of the genome, is used to 'fingerprint' each species and thus serve as an identification tool for species of Trichoderma. This research will be used by plant pathologists who are working to develop effective biological ways to control of plant diseases. Technical Abstract: A chronology is presented that charts the development of a genus and species concept in Trichoderma. Sixty species of Trichoderma have been described and 82 species of Trichoderma and their teleomorphs, Hypocrea species, have been included in phylogenetic analyses. Sequences of the ITS region of rDNA and translation-elongation factor 1-' have been deposited for all of those species making species identification relatively easy. Exploration of new niches, such as endophytes, and new geographic locations will result in a substantial increase in the number of species of Trichoderma. Molecular phylogenetic analyses have revealed the existence of more species than have been recognized on the basis of morphology alone but have provided a phylogenetic framework from which predictions of biological activity can be made. DNA sequence data show that Trichoderma and Hypocrea are phylogenetically indistinguishable and most of the named Trichoderma species have been linked to teleomorphs in Hypocrea. The sectional subdivisions of Trichoderma have not stood up to molecular phylogenetic analysis although the names of sections are useful as morphological descriptors because of the tendency for phylogenetic lineages to be characterized by morphology. Trichoderma is usually thought of as being a genus of free-living soil fungi but evidence suggests that Trichoderma species may be opportunistic, avirulent plant symbionts as well as being parasites of other fungi. Trichoderma species are now known to be the dominant endophytes found within trunks of asymptomatic cocoa trees. |
