Beech mushroom (Hypsizygus marmoreus) is one of the most popular mushrooms in Japan, China, and Korea because of its delicious taste, nutritious value, and unique crunchy texture. In 2018-2019, unusual signs on the mushroom were observed in mushroom farms in Gyeongnam Province. The main signs were the inhibition of mycelial growth and primordial formation on the surface of mushroom media. When green mold caused contamination at early stage, the rate of pinhead formation by the mushroom greatly decreased to 46.5-71.5%. Conidia of the causal green mold were ellipsoidal, dark green, and measured 2.0-3.1μm long. The optimum temperature for mycelial growth of the green mold was 25℃. The phylogenetic tree obtained from the internal transcribed spacer (ITS) rDNA sequences showed that the isolated green mold corresponded to Penicillium brevicompactum (100.0%). This is the first report of green mold contamination caused by P. brevicompactum on H. marmoreus.
