RESUMO
Based on morphological and phylogenetic analyses, an ectomycorrhizal fungus collected from Jiangxi, China, is described as a new species. R. atrofuscus is morphological characterized by a dark gray to black pileus, white to pale yellowish white hymenophore, a grayish brown to pale yellow context, which turning orange-yellow to rusty yellow when injured, a prominently and coarsely white to pale yellow to black reticulation on upper 3/4 or entire stipe, grayish yellow to pale yellow to yellowish brown basidiospores in KOH with measuring (7-)7.5-13(-13.5) × (3-)3.5-5(-5.5) µm. Phylogenetic analysis results showed that R. atrofuscus formed an independent lineage within Retiboletus. Descriptions and hand drawings of the new species and comparisons with similar species are presented.
