Four new species of Russula subsect. Cyanoxanthinae from China (Russulales, Russulaceae)

Four new species of Russula subsect. Cyanoxanthinae, viz. Russula atrochermesina Y.L. Chen & J.F. Liang, R. lavandula Y.L. Chen, B. Chen & J.F. Liang, R. lilaceofusca Y.L. Chen & J.F. Liang and R. perviridis Y.L. Chen, B. Chen & J.F. Liang, from China are proposed, based on morphological and molecular evidence. Russula atrochermesina can be distinguished by its violet pileus with tuberculate-striate margin, distant lamellae that stain greyish-yellow when bruised, basidiospores ornamented by isolated warts, wide hymenial cystidia on lamellae edges, cystidia content negative reaction in sulphovanillin and branched subterminal cells in pileipellis. Russula lavandula has a purplish-white to violet red pileus with a yellow centre, frequently present lamellulae and furcations, stipe often with pale yellow near the base, isolated basidiospores ornamentation and unbranched cuticular hyphal terminations, while R. lilaceofusca is characterised by its lilac brown to dark brown pileus, crowded lamellae with lamellulae and furcations, stipe often turning reddish-yellow when bruised, subreticulate basidiospores ornamentation and clavate hymenial cystidia often with capitate appendage whose contents that change to reddish-black in sulphovanillin. Russula perviridis is characterised by its large basidiomata, smooth pileus surface, frequently present lamellulae and furcations, stipe with yellow-brown tinge, globose to broadly ellipsoid basidiospores with subreticulate ornamentation, long hymenial cystidia that turn greyish-black in sulphovanillin and symbiotic with Quercus semecarpifolia. Phylogenetic analyses, based on multi-gene ITS+LSU+mtSSU+rpb2, indicate that R. atrochermesina, R. lavandula, R. lilaceofusca and R. perviridis are closely related to R. pallidirosea and R. purpureorosea, R. banwatchanensis, R. lakhanpalii and R. nigrovirens, respectively.