Redefining the clade Spirale of the genus Trichoderma by re-analyses of marker sequences and the description of new species

Abstract

During a survey of the genus Trichoderma in the Brazilian ecosystem Restinga, 22 strains related to Trichoderma spirale were found on the basis of identities of tef1, the molecular marker used to discriminate species of this genus. Trichoderma spirale was described in 1991 and since then four species related to it were described and later on added to the clade Spirale. Searches for tef1 sequences assigned to T. spirale or related species in public databases recovered sequences with identities ranging from 93.5 to 100 % in comparison with the tef1 sequences of the type of the species. It clearly shows that the species diversity in this clade is higher than anticipated. These sequences originated from strains obtained in different continents suggesting that T. spirale is a highly diverse worldwide-distributed species. We present results indicating that most of these tef1 sequences represent 11 novel putative species in the Spirale clade delimited with a tef1 alignment using the programme ASAP, which is able to distinguish closely related species. In this study, two species from the Restinga ecosystem are described as Trichoderma gilbertogili sp. nov. and Trichoderma rubropilosum sp. nov. based on a polyphasic approach. The potential of these newly described species as biological control agents of two plant pathogens was assessed based on in vitro antagonism assays. Besides the description of two novel species, the other taxonomic novelties we proposed are the invalidation (nomina invalida) of the names T. inaequilaterale and T. supraverticillatum, and the transfer of T. hunanense and Trichoderma longisporum to a new clade for which we propose the name Hunanense. This study significantly improved our comprehension of the diversity in the clade Spirale.