Clarifying the identity of marketed edible fungus Huotanjun (Burnt Charcoal Mushroom) in southern China

Abstract

Huotanjun (Burnt Charcoal Mushroom) is a group of edible mushrooms widely hunted and eaten in southern China. Taxonomically they belong to Russula sect. Nigricantinae. Confusion with the fatal R. subnigricans cause many poisoning incidents in Asia. For a long time, European names were used in Asia but the Asian genotypes are not the same as European species. We studied specimens collected from markets and the field in southern China. Analysis of four DNA loci (ITS, nc LSU, TEF1-α, RPB2) showed that except for a specimen of R. adusta from subalpine Abies forest in southwestern China, all the specimens represent species different from European and North American ones, suggesting prevalent continental endemism in this group. Four new species were described. Among them R. sinoadusta and R. zhuzuijun are Asian counterparts of R. adusta; R. brunneocystidia and R. huotanjun are closely related with European R. densifolia and R. fuliginosa. These species are highly similar to their European siblings and the morphological differences are very subtle. Using multi-locus data, for the first time, we determined the phylogenetic position of R. subnigricans. It was nested in R. sect. Nigricantinae and sister to R. latolamellata, a species also having distant lamellae and only reddening context. Geographically except for R. sinoadusta known only from China, all species are shared by China and Japan. We analyzed presence/absence of the diagnostic toxin of R. subnigricans cycloprop-2-ene carboxylic acid for 12 species and did not detect the polymeric products in any of them but R. subnigricans. Nevertheless, considering several potentially edible species also have spaced lamellae and only reddening discolouration which can be easily confused with R. subnigricans, we strongly recommend to only eat species with decidedly blackening context and gills.