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Title: EXAMINATION OF TRICHODERMA PHYLOGENIES DERIVED FROM RIBOSOMAL DNA SEQUENCE DATA

Author
item DODD-WILSON, SARAH - UNIVERSITY OF AUCKLAND
item CROWHURST, ROSS - MT. ALBERT RES. NZ
item RODRIGO, ALLEN - UNIV. OF WASHINGTON
item Samuels, Gary
item HILL, ROBERT - RUAKURA RES. STATION NZ
item STEWART, ALISON - LINCOLN UNIVERSITY NZ

Submitted to: Mycological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The development of management strategies to control fungal diseases through the use of biological control agents is hindered by lack of knowledge about species in the genus Trichoderma. In addition, a species of Trichoderma being used in the biological control of plant pathogens has been confused with species of Trichoderma that is causing a disease in commercial mushroom beds. This research explores the relationships among 50 isolates of Trichoderma by comparing morphological and molecular data. In general these kinds of data products the same results in delimiting and defining species. The species of Trichoderma useful in biological control was shown to be a different species than the species causing a disease in mushroom beds. These results will be useful to agricultural scientists who to distinguish species useful in biological control from those that may be hazardous to the commercial mushroom industry.

Technical Abstract: Ribosomal DNA sequences were assessed for their utility in distinguishing between individuals within the genus Trichoderma and for their robustness in resolving the phylogenetic relationships of these individuals. DNA sequence from the D2 region of the 28S rRNA gene was determined for 50 Trichoderma isolates representing seven species. Eight sequence types existed among the 50 isolates and these were mostly consistent with groupings based on morphology. However, sequence variability with the D2 region alone was not sufficient to provide a reliable phylogeny. Sequence from the ITS1, 5.8S and ITS2 regions were subsequently determined for 18 of the 50 isolates. Eight distinct ITS sequence types were detected among these 18 isolates. The ITS sequence types were generally consistent with morphology. ITS sequence data supported the identification of the Th3 T. harzianum group of Muthumeenakshi et al. (1994) as T. atroviride. The data also confirmed that the biocontrol strains of this study were different from strains causing disease in the mushroom industry. Results from the phylogentic analysis stress the importance of testing the robustness of data used to predict phylogenies. Two ITS sequence data sets for the same group of isolates produced different pylogenies. Congruence analysis detected T. inhamatum (GJS90-90) was corrupting tree topologies and 'first order pruning' was performed by removing its sequence from the two ITS data sets. Subsequent differences in the topologies of pruned ITS1 and ITS2 trees were attributed to a lack of phylogenetic information in the ITS2 sequence region.ITS sequences differentiated morphologically distinct individuals within Trichoderma, but did not resolve all relationships.