Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2009
Publication Date: January 1, 2010
Citation: Samuels, G.J., Ismaiel, A.A., Bon, M., De Respinis, S., Petrini, O. 2010. Trichoderma asperellum reconsidered: two cryptic species. Mycologia. 102(4)944-966.
Interpretive Summary: Fungi in the genus Trichoderma are used to control diseases of plants. Correct identification of species is critical in using them as biocontrol agents. Identification of species using their appearance in the microscope is no longer reliable. In this research one species that serves as an biological control agent was found to consist of two similar-appearing species. These species can be rapidly distinguished using DNA sequences as well as by the proteins each species produces. This work will be useful to plant pathologists who search for fungi to control plant pathogens.
Analysis of a world-wide collection of strains of Trichoderma asperellum using multilocus genealogies of four genomic regions (tef1, rbp2, act, ITS1, 2, 5.8s), sequence polymorphism-derived (SPD) markers, matrix-assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI-TOF MS) of peptides, and classical mycological techniques reveal two morphologically cryptic sister species within T. asperellum, and a third morphologically distinct species. Trichoderma asperellum, T. asperelloides sp. nov., and T. yunnanense are described. Trichoderma asperellum and T. asperelloides have wide sympatric distribution on multiple continents while T. yunnanense is represented by a single strain from China. Several strains reported in the literature or represented in GenBank as T. asperellum are reidentified as T. asperelloides. Four molecular SPD typing patterns (I—IV) were found over a large geographic range. Patterns I—III were produced by T. asperellum and Pattern IV by T. asperelloides and T. yunnanense. Pattern I was found in all 5 continents sampled, Pattern II only in Cameroon (Central Africa) and Peru, and Pattern III from West and Central Africa, Asia and North America. All SPD II pattern strains formed a strongly supported subclade within the T. asperellum clade in the phylogenetic tree based on rbp2 and MLS and join with diversity in MALDI-TOF MS to suggest that further speciation is underway within T. asperellum. MALDI-TOF MS distinguishes T. asperellum, T. asperelloides and T. yunnanense by single-link agglomerative clustering.