PHYLOGENY OF THE GENUS TRICHODERMA BASED ON SEQUENCE-ANALYSIS OF THE INTERNAL TRANSCRIBED SPACER REGION-1 OF THE RDNA CLUSTER

Sequences of the internal transcribed spacer region 1 (ITS1) of the ri bosomal DNA were used to determine the phylogenetic relationships of s pecies of Trichoderma sect. Pachybasium. To this end. 85 strains-inclu ding all the available ex-type strains-were analyzed. Parsimony analys is demonstrated that the section is nonmonophyletic, distributing the 85 strains among three main groups that were supported by bootstrap va lues. Group A comprises two clades (A1 and A2), with A1 including T. p olysporum, T. piluliferum, and T. minutisporum, while A2 included T. h amatum, T. pubescens, and T, strigosum in addition to species previous ly included in sect. Trichoderma (i.e., T. viride, T. atroviride, and T. koningii). The ex-type strain of T. fasciculatum formed a separate branch basal to clade A. Clade B contained the sect. Pachybasium membe rs T. harzianum, T. fertile, T. croceum, T. longipile, T. strictipile, T. tomentosum, T. oblongisporum, T. flavofuscum, T. spirale, and the anamorphs of Hypocrea semiorbis and H. cf. dgelatinosa. Sequence diffe rences among clades Al, A2, and B were in the same order of magnitude as between each of them and T. longibrachiatum, which was used as an o utgroup in these analyses. Sequence differences within clades Al, A2, and B were considerably smaller: in some cases (i.e., T. virens and T. flavofuscum; T. strictipile and H. cf. gelatinosa), the ITS1-sequence s were identical, suggesting conspecifity. In other cases (e.g., T. cr assum and T. longipile; T. harzianum, T. inhamatum, T. croceum, T. fer tile, and H. semiorbis; T. hamatum and T. pubescens; and T. viride, T. atroviride, and T. koningii) differences were in the range of 1-3 nt only, suggesting a very close phylogenetic relationship. The sequence of a previously described aggressive mushroom competitor group of T. h arzianum strains (Th2) was strikingly different from that of the ex-ty pe strain of T. harzianum and closely related species and is likely to be a separate species. (C) 1998 Academic Press.