Notes on two new species of Russula subsect. Cyanoxanthinae (Russulaceae, Russulales) from southern China

Two new species of Russula subsect. Cyanoxanthinae, collected from tropical and subtropical regions of China, are proposed based on morphological and multi-gene phylogenetic data. Russula icterina is characterized by its green pileus, lamellae with frequent furcations but without lamellulae, basidiospores ornamented with isolated warts with indistinct and inamyloid suprahilar spots, widely dispersed hymenial cystidia rarely with appendages, terminal cells with attenuated or constricted apexes in the pileipellis, one-celled and fusiform pileocystidia without apices that turn grayish black in sulfovanillin, and presence in low-altitude broad-leaved forests dominated by Castanopsis sclerophylla and Quercus acutissima. Russula purpureobrunnea is characterized by its purplish pink to purplish brown pileus, lamellae mixed with lamellulae some with furcations, basidiospores ornamented with isolated warts, clavate or lageniform hymenial cystidia with capitate or mucronate appendages, metachromatic pileipellis with apically attenuated or constricted terminal cells, one-celled pileocystidia that turn grayish black in sulfovanillin, and presence in Pinus yunnanensis, Keteleeria fortunei, Lithocarpus dealbatus, and Quercus spp. mixed forests. Comprehensive morphological descriptions, illustrations, and comparisons with morphologically and phylogenetically related species are provided.