Authors: Korhonen, Mauri & Liimatainen, Kare & Niskanen, Tuula
Journal: Karstenia, Volume 49 (2009), Issue 2, pages 41-60.
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Key words: taxonomy, Boletales, Boletus, IGS, ITS
Abstract: A detailed study of morphological characters of the species in the Boletus sect.Boletus occurring in Finland was carried out. Consequently six species were separated: B. pinophilus, B. reticulatus, and four species in the B. edulis group: B. edulis, B. betulicola, B. aff. reticulatus and B. pinetorum M. Korhonen spec. nov. In addition, the identity of B. edulis var. arcticus is discussed. The species presented in this study have good distinguishing macro- and especially microscopical characters as well as differences in their ecological requirements. The most useful microscopical characters used for distinguishing the species are: shape of the spores, caulocystidia, and characters of pileipellis hyphae. A phylogenetic study of the species was also undertaken using the molecular markers ITS1 and ITS2. In addition, the IGS1 region of B. edulis coll. and B. pinophilus was studied. A total of 46 sequences were generated. The IGS1 region was shorter than ITS1-5.8S-ITS2 region and interestingly contained less intraspecifi c variation than ITS1 and ITS2. In our analysis Boletus pinophilus, B. reticulatus, and B. edulis s. lato formed well supported lineages but as in previous studies, relationships inside the B. edulis group remained unresolved. Based on their distinct macro- and microscopical characters, however, we consider the taxa within B. edulis groups as separate species.