A specific mycelial structure formed by Rhizoctonia and other fungi on cellulose membranes

Abstract

　When grown on a cellulose membrane laid on Czapek agar without sugars (CCMA), Rhizoctonia solani formed a specific mycelial structure under the membrane. The structure was also formed by Rhizoctonia spp., Sclerotium spp., Sclerotinia sclerotiorum, Corticium rolfsii, Nakataea sigmoideum var. irregulare but not by other fungi tested. The structure was not formed on media containing such sugars as glucose, sucrose or galactose, but was formed on media with trehalose or mannitol. The structure was not formed under filter membranes of cellulosic fibriform or polycarbonate. When a double layer of different membranes was put on agar medium, the structure was produced only beneath the cellulose membrane. However, when a polycarbonate filter membrane was set on the cellulose membrane, the structure was produced between the two. Validamycin A, an antibiotic for Rhizoctonia disease control, prevented the formation of the structure at 0.01 μg/ml in CCMA.