Three new species of Trichoderma in the Harzianum and Longibrachiatum lineages from Peruvian cacao crop soils based on an integrative approach

The hyperdiverse genus Trichoderma is one of most useful groups of microbes for a number of human activities, and their accurate identification is crucial. The structural simplicity and lack of distinctive phenotypic variation in this group enable the use of DNA-based species delimitation methods in combination with phylogenies (and morphology when feasible) to establish well-supported boundaries among species. Our study employed a multilocus phylogeny and four DNA-based methods (automated barcode gap discovery [ABGD], statistical parsimony [SPN], generalized mixed Yule coalescent [GMYC], and Bayesian phylogenetics and phylogeography [BPP]) for four molecular markers (acl1, act, rpb2, and tef1) to delimit species of two lineages of Trichoderma. Although incongruence among these methods was observed in our analyses, the genetic distance (ABGD) and coalescence (BPP) methods and the multilocus phylogeny strongly supported and confirmed recognition of 108 and 39 different species in the Harzianum and Longibrachiatum lineages, including three new species associated with cacao farms in northern Peru, namely, T.awajun, sp. nov., T.jaklitschii, sp. nov., and T.peruvianum, sp. nov. Morphological distinctions between the new species and their close relatives are primarily related to growth rates, colony appearance, and size of phialides and conidia. This study confirmed that an integrative approach (DNA-based methods, multilocus phylogeny, and phenotype) is more likely to reliably verify supported species boundaries in Trichoderma.