Trichoderma matsushimae and T. aeroaquaticum: two aero-aquatic species with Pseudaegerita-like propagules

Abstract

Four isolates tentatively identified as Pseudaegerita matsushimae on the basis of the morphology of bulbil-like propagules were collected from substrates submerged in water in Thailand and Japan. In culture studies the two Thai isolates were found to produce phialoconidia on conidiogenous cells and phialoconidiophores whose morphology was similar to that of Trichoderma. Phylogenetic analysis based on D1/D2 regions of LSU rDNA sequences showed that the four isolates were nested in Hypocrea/Trichoderma (Hypocreales) while P. corticalis, the type species of Pseudaegerita, belongs to Hyaloscypha (Helotiales). Preliminary analysis by ISTH Web tools based on 5.8S-ITS rDNA and phylogenetic analysis based on rpb2 and tef1-int4 genes showed that the isolates have specific sequences of Trichoderma (anchors 1–5) and belong to the Hamatum clade but they grouped apart from any known species of Trichoderma. The sequences of the tef1-int4 gene, which were amplified from the authentic specimen of P. matsushimae (IMI 266915), also showed that it belongs to the Hamatum clade closely clustering with T. yunnanense but separate from our four isolates. The morphology of P. matsushimae (IMI 266915), especially the sizes of phialides and phialoconidia, were different from T. yunnanense. Thus, we conclude that IMI 266915 and our isolates are to be assigned to two different species in the Hamatum clade of Trichoderma, although both species have similar morphology of bulbils and phialoconidia. Morphology and molecular data revealed that P. matsushimae should be assigned to the genus Trichoderma as T. matsushimae and the Thai and Japanese isolates are placed in T. aeroaquaticum sp. nov. This finding supports the interpretation that aero-aquatic fungi have evolved from terrestrial fungi. We assume that these fungi probably were derived from typically soil-inhabiting species of Trichoderma; an adaptation to aquatic environments is shown by formation of bulbil-like propagules floating on water.

Key words:

• evolution
• freshwater
• Hamatum clade
• Hypocreales
• systematics
• tef1-int4

Acknowledgments

We gratefully thank Dr Brian Spooner, the curator of the Mycology Herbarium, Royal Botanic Gardens, Kew, for loan and permission for DNA extraction of the IMI 266915 (Pseudaegerita matsushimae). We sincerely thank Dr Gerard J.M. Verkley, curator of filamentous fungi of Centraalbureau voor Schimmelcultures (CBS), for providing the CBS 125398 (=NBRC 108806), CBS 125399 (=NBRC 108807) (Trichoderma asperelloides) and CBS 121219 (=NBRC 108643) (Trichoderma yunnanense) and Dr Josepa Gené, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, for advice about culture study of Pseudaegerita. We thank Dr Yoshimichi Doi, the Society for Mycology Education, and Dr Seiji Tokumasu, Sugadaira Montane Research Center, University of Tsukuba, for comments about this new species (T. aeroaquaticum) and Dr Yousuke Degawa, Sugadaira Montane Research Center, University of Tsukuba, for helping in collecting samples in Sugadaira Montane Research Center. We also thank Ms Yukiko Tabuchi, Ms Kuniko Shimamura and Ms Yoshiko Mibu, NBRC, for technical support.