Four new species of Entoloma from Kon Chu Rang Nature Reserve and Ta Dung National Park were discovered during an investigation of the diversity of the mycobiota of Central Vietnam and are described here on the base of the molecular and morphological data. Phylogenetic analysis was based on nrITS1-5.8S-ITS2, nrLSU and tef1α regions. Illustrated descriptions of their macro- and microscopic features and discussion on similar taxa are given. Entoloma cycneum and E. peristerinum belong to the subgenus Cubospora. They are morphologically similar species and are characterized by white or whitish basidiomata with yellowish or beige tinges and with mainly smooth, glabrous, and hygrophanous pileus, longitudinally fibrillose or fibrillose-scaly white stipe, cuboid spores, and more or less cylindrical cheilocystidia, arising from hymenophoral trama. Entoloma peristerinum posseses initially more coloured beige conical pileus, discolouring to white with age and drying. The pileus of E. cycneum is initially white, hemisphaerical to convex, usually with thin pubescence near the margin. The species can be recognized also by the cheilocystidia form: serrulatum-type in E. cycneum vs. porphyrogriseum-type in E. peristerinum. Another two species belong to the subgenus Leptonia. Entoloma tadungense is close to E. percoelestinum from which it differs by smaller spores with pronounced angles, presence of the cheilocystidia, and the lilac discolouration of the stipe. E. dichroides is named after its similarity to E. dichroum, a dark blue coloured species with pronouncedly angled basidiospores. It is distinguished by the basidiospores form-irregularly 5(-6) angled with elongated apiculus, as well as by absence of the cheilocystidia and darker basidiomata with conical pileus. The article also describes the history of the study of the genus Entoloma in Vietnam with a list of 29 species mentioned in the publications for this country.
Keywords: Entolomataceae; Kon Chu Rang Nature Reserve; Ta Dung National Park; molecular phylogeny; new species; systematics; taxonomy.