Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2002
Publication Date: 2/1/2004
Citation: Chaverri, P., Castlebury, L.A., Samuels, G.J., Geiser, D.M. Multilocus phylogenetic structure within the trichoderma harzianum/hypocrea lixii complex. Molecular Phylogenetics and Evolution. Vol.88(4)p.427,2004.
Interpretive Summary: Fungi in the genus Hypocrea, often as their Trichoderma asexual states, are useful in the biological control of plant diseases. One species, Trichoderma harzianum, is particularly effective and has potential for enhancement of plant growth and resistance to plant pathogens. Species of Trichoderma are difficult to define because of their lack of morphology. Thus it is necessary to analyze characteristics of the DNA of these fungi in order to define species and determine which relationships among isolates. In this paper several genes were sequenced of strains of the asexual fungus Trichoderma harzianum as well as strains from the sexual Hypocrea lixii. These data were analyzed both separately and together to determine which if this group includes more than one species. The results suggested that these isolates compose a complex of closely related species. This work will be used by plant pathologists who are working to develop more effective strains of fungi that can be used in the biological control of plant diseases.
Technical Abstract: Trichoderma harzianum is an ubiquitous species in the environment and is effective in the biological control of plant pathogenic fungi. T. harzianum has not been linked unequivocally to its sexual state nor has its phylogeny been studied in detail. It has been suggested that T. harzianum is a species complex based on the phenotypic and genotypic variability encountered. On the basis of morphological and cultural characters and DNA sequence data analysis of four genes (ITS rDNA, translation elongation factor 1- , calmodulin and -actin), Hypocrea lixii was found to be the sexual state of T. harzianum. Both the asexual and sexual states of this species have wide geographic distributions. Phylogenetic analysis showed that T. harzianum/H. lixii is a cohesive group that is supported by bootstrap values higher than 95%. Principles of genealogical concordance indicated that T. harzianum/H. lixii is a complex of independent monophyletic lineages, but no diagnostic biological distinctions were identified that justify formal taxonomic recognition for the different lineages.