A fifty-locus phylogenetic analysis provides deep insights into the phylogeny of Tricholoma (Tricholomataceae, Agaricales)

Abstract

As an ectomycorrhizal fungal genus that contains matsutake and other edible mushrooms, Tricholoma has great economic and ecological significance. However, the phylogenetic relationships within the genus remain unsettled. To clarify the infrageneric relationships of Tricholoma, including the identification of monophyletic subgenera and sections, three phylogenetic analyses were conducted employing single-locus(ITS), five-locus (ITS/ RPB2/EF-1α/MCM7 /mtSSU) and 50-locus (45 single-copy ortho logous gene splus the aforementioned ones)DNA nucleotide sequences. Our data indicated that ITS sequences could serve the species delimitation of Tricholoma in most cases and monophy letic groups recognition in somecases, and the five-locus data set could resolve a section-level phylogeny of this genus, while the 50-locus data set could clarify the delimitation of subgenera and settle the relationships among sections with in this genus. A fifty-locus data set was firstly employed to constructa robust phylogeny of Tricholoma. Based on this, a new infrageneric arrangement for the genus Tricholoma, with four subgenera, of which two are in accordance with the previous subgenera Pardinicutis and Sericeicutis, and eleven sections, is suggested. Subgenus Pardinicutis, occupying the basal position, only harbors sect. Pardinicutis, while the subg. Sericeicutis comprises sects. Lasciva and Sericella located at the sub-basal position with good support. Subgenus Terrea is newly erected here and consists of sect. Terrea, sect. Atrosquamosa and two as yet unnamed phylogenetic lineages. Besides an unnamed section-levellineage, subg. Tricholoma consists of sects. Genuina, Muscaria, Rigida, Tricholoma, Fucata and Matsutake, of which the two latter are newly proposed. The previously defined subg. Contextocutis is clustered within subg. Tricholoma and is a synonym of the latter. Tricholoma colossus, T. acerbum and their allies, which used to be allocated insect. Megatricholoma (orgenus Megatricholoma), are relocated to sect. Genuina since they form a strongly supported monophyletic group and share rusty or black spot son lamel lae with other species in this section. Taxonomic descriptions of the new infrageneric taxa and a key to subgenera and sections of the genus Tricholoma are presented.