Taxonomic relationships among non-macrocystidiate taxa of Lactarius subg. Russularia from Europe with special reference to species from Greece

Members of the ectomycorrhizal genus Lactarius form symbiotic relationships with a wide range of plant species. For the purposes of this study, 29 specimens originally assigned to L. atlanticus, L. serifluus and L. subumbonatus were examined by including all pertinent available material from Greece. The detailed study of macroscopic and microscopic characteristics by using compound optical, differential interference contrast (DIC) and scanning electron microscopy in combination with molecular approaches (ITS1-5.8S-ITS2 rDNA sequencing) permitted a clear separation between L. atlanticus and L. subumbonatus, while their basidiospore shape and height of ornamentation were found to be of diagnostic value. Moreover, the morphological delimitation between the specimens identified as L. serifluus and L. subumbonatus is not clear, and these specimens were intermixed into the same phylogenetic cluster with high support. Thus, the latter name should be considered as a synonym of the former. As concerns other related taxa of L. subg. Russularia, the American L. rubidus and L. subserifluus demonstrated relatively high evolutionary affinity with European collections of L. serifluus/L. subumbonatus and L. atlanticus, respectively.