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Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Molecular approaches including internal transcribed spacer (ITS) sequences of ribosomal DNA, universal primer polymerase chain reaction (UP-PCR) fingerprinting, and DNA–DNA hybridization were used to study the genetic relatedness of species within Trichoderma sect. Pachybasium. In the analysis of ITS and 5.8S sequences of ribosomal DNA, parsimony analysis demonstrated that forty-one strains were distributed into five main groups supported by high bootstrap values. The species of Trichoderma sect. Pachybasium were clustered into groups I, II, and IV, with the strains of Trichoderma fasculatum and Trichoderma strictipile forming a separate branch, an independent group V. Some species within each group showed nearly identical sequence differences (fewer than 1–3 bp). UP-PCR and DNA–DNA hybridization were further used to clarify the genetic relatedness of these species with highly similar ITS sequences. Highly similar or identical UP-PCR profiles and high values of DNA complementarity (>70%) were observed among some species, Trichoderma hamatum and Trichoderma pubescens; Trichoderma croceum,Trichoderma polysporum and Trichoderma album; Trichoderma crassum and Trichoderma flavofuscum; and Trichoderma strictipile and Trichoderma fasciculatum. Although every species can be differentiated morphologically, the species showed highly similar molecular characteristics in the above cases, indicating that they could be conspecific. However, in some cases (Trichoderma longipile, T. crassum and T. flavofuscum; Trichoderma fertile and Trichoderma minutisporum; Trichoderma tomentosum, Trichoderma inhamatum and Trichoderma harzianum) there were discriminative patterns of UP-PCR and (or) low levels (<50%) of DNA–DNA hybridization; even their ITS sequences were similar, suggesting a closely phylogenetic relationship.Key words: fingerprinting, ITS sequencing, DNA–DNA hybridization, taxonomy, Trichoderma.Nous avons eu recours à des approches moléculaires incluant les séquences d'espaceur interne transcrit (ITS) d'ADN ribosomal, la caractérisation par réaction de polymérase en chaîne à amorce universelle (UP-PCR), et l'hybridation ADN–ADN, afin d'étudier la parenté génétique d'espèces appartenant à Trichoderma sect. Pachybasium. Dans l'analyse de séquences d'ADN ribosomal d'ITS et de 5,8S, une analyse par parcimonie a démontré que quarante-et-une souches pouvaient être classées dans cinq groupes principaux soutenus par des valeurs de bootstrap élevées. Les espèces de Trichoderma sect. Pachybasium ont été rassemblées dans les groupes I, II et IV, alors que les souches de Trichoderma fasculatum et Trichoderma strictipile ont formé un embranchement distinct, un groupe V indépendant. Certaines espèces à l'intérieur de chaque groupe affichaient des différences de séquences quasiment identiques (moins de 1–3 pb). Les analyses de UP-PCR et d'hybridation se sont rajoutées afin de clarifier la parenté génétique des ces espèces ayant des séquences ITS très semblables. Nous avons observé des profils de UP-PCR fort semblables ou identiques ainsi que des valeurs élevées de complémentarité d'ADN (>70%) parmi certaines espèces, notamment Trichoderma hamatum et Trichoderma pubescens; Trichoderma croceum,Trichoderma polysporum et Trichoderma album; Trichoderma crassum etTrichoderma flavofuscum; et finalement Trichoderma strictipile et Trichoderma fasciculatum. Bien que chacune des espèces pouvaient être différentiées selon la morphologie, les espèces mentionnées ci-haut affichaient des caractéristiques moléculaires fortement semblables, ce qui indique qu'elles pourraient être conspécifiques. Cependant, dans certains cas (Trichoderma longipile, T. crassum et T. flavofuscum; Trichoderma fertile et Trichoderma minutisporum; Trichoderma tomentosum, Trichoderma inhamatum et Trichoderma harzianum) nous avons obtenu des patrons de UP-PCR discriminants et/ou de bas niveaux (<50%) d'hybridation ADN–ADN, même si leurs séquences ITS étaient proches, ce qui signalait l'existence d'un lien phylogénétique rapproché.Mots clés : caractérisation, séquençage d'ITS, hybridation ADN–ADN, taxonomie, Trichoderma.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]