Authentication of the Cladosporium strains deposited at the Mycotheca Universitatis Taurinensis (MUT): a polyphasic approach

Cladosporium is one of the largest and most heterogeneous genera of hyphomycetes, with a cosmopolitan distribution. Since 2007 extensive systematic reviews of this genus have been carried out and new species have been introduced. To date, the genus Cladosporium, with about 120 strains preserved, is one of the most represented in the MUT collection. These strains have very different geographic origins and various substrate of isolation (e.g. soil, marine environment, air, ancient frescoes, etc.), many of them have been identified in the past by a traditional morphological approach, mainly referring to the three most common species (i.e. Cladosporium cladosporioides, C. herbarum and C. sphaerospermum). The aim of the present study was to authenticate about 100 strains of Cladosporium spp. deposited at the MUT by a polyphasic approach, combining morphological and physiological observations and molecular analysis. On the basis of literature data, the actin gene (primers ACT-512F and ACT-783R) was chosen as the most appropriate molecular marker for identification at the specific level of the systematic group taken into consideration. In most cases (about 65%) the specific identification was renewed. Actually, the authentication process made it possible to confirm the identification only for 35% of cases and to assign a specific epithet to about 10% of strains, previously identified to the genus level only. In addition, four species (C. perangustum, C. pseudocladosporioides, C. ramotenellum and C. tenellum), previously not present in the MUT collection, were identified. The present study, which is part of a larger project of authentication of the strains deposited at the MUT, pointed out that a polyphasic approach is crucial when you have to face the identification of cryptic species or taxa subjected to systematic review.