Distinguishing edible mushroom (Russula griseocarnosa) and poisonous mushroom (Russula sp.) in Quang Ninh province, Vietnam

Russula griseocarnosa occurs naturally in Southern China and Northeast Vietnam, where it is widely used as food. In Quang Ninh province, this edible mushroom species (Nấm chẹo/nam cheo) grows wild in forests with Engelhardia roxburghiana trees and some chestnut species. However, in these forests there is another Russula species that is toxic and closely resembles R. griseocarnosa. The toxic species is called red mushroom (nam xop do), and it causes symptoms of dizziness and vomiting when eaten. This study aimed to provide basic data to distinguish the two Russula species. Based on the sequence of the ITS gene, it was concluded that the edible mushroom is Russula griseocarnosa, while the red mushroom is an unidentified Russula species. Morphological comparison of the two species revealed some distinguishing features, namely (1) nam cheo caps are a lighter color (pink or brick red) than red mushroom (red or bright red); (2) the mature cap of nam cheo is much thicker (1.5-2.1 cm) than that of red mushroom (1.0-1.2 cm); (3) The flesh inside the stalk of nam cheo is spongy and grayish white or gray in color, while the flesh inside the red mushroom stalk is white and not spongy. These findings will help collectors and housewives more readily distinguish between the nam cheo and red mushroom.