Trichoderma biodiversity in China: evidence for a North to South distribution of species in East Asia.

Towards assessing the biodiversity and biogeography of Trichoderma, we have analyzed the occurrence of Trichoderma species in soil and litter from four areas in China: North (Hebei province), South-East (Zhejiang province), West (Himalayan, Tibet) and South-West (Yunnan province). One hundred and thirty five isolates were grouped according to tentative morphological identification. A representative 64 isolates were verified at the species level by the oligonucleotide barcode program TrichO Key v.1.0 and the custom BLAST server TrichoBLAST, using sequences of the ITS1 and 2 region of the rRNA cluster and from the longest intron of the tef1 (translation elongation factor 1-alpha) gene. Eleven known species (Trichoderma asperellum, T. koningii, T. atroviride, T. viride, T. velutinum, T. cerinum, T. virens, T. harzianum, T. sinensis, T. citrinoviride, T. longibrachiatum) and two putative new species (T. sp. C1, and T. sp. C2), distinguished from known species both by morphological characters and phylogenetic analysis, were identified. A significant difference in the occurrence of these species was found between the North (Hebei) and South-West (Yunnan) areas, which correlates with previously reported species distributions in Siberia and South-East Asia, respectively. As in previous studies, T. harzianum accounted for almost half of the biodiversity; although, in this study, it was exclusively found in the North, and was predominantly represented by an ITS1 and 2 haplotype, which has so far been rarely found elsewhere. This study therefore reveals a North-South gradient in species distribution in East Asia, and identifies Northern China as a potential center of origin of a unique haplotype of T. harzianum.