In 1997, during a study to determine the pathogenic fungi on Johnsongrass (Sorgum halepense) in the Yusufeli District of Artvin Province, 10 isolates of a Rhizoctonia sp. were obtained from necrotic roots. In anastomosis tests, Johnsongrass isolates fused at low frequency with the Rhizoctonia sp. (teleomorph: Waitea circinata var. circinata) and R. oryzae (teleomorph: W. circinata var. oryzae), and at high frequency with R. zeae (teleomorph: W. circinata var. zeae). Test isolates of the Rhizoctonia sp. (W. circinata var. circinata), R. oryzae, and R. zeae (isolate nos. W616, 231, and 590, respectively) were provided by R. H. Leiner (University of Alaska Fairbanks). In addition, Johnsongrass isolates were identified as R. zeae based on colony morphology of the vegetative state. Pathogenicity of two isolates (JR-3 and JR-8) was determined on Johnsongrass seedlings at 25°C. Six seeds were sown in a 10-cm-diameter pot containing a sterile soil mixture of coarse sandy loam and sand (1:1, vol/vol). Each pot was a replicate and each treatment was replicated four times. Four-week-old Johnsongrass seedlings were inoculated by gently removing the soil mixture from one side of the stem, placing a colonized potato dextrose agar (PDA) 4-mm-diameter plug in direct contact with the base of the stem, and covering the inoculum with the soil mixture. A sterile, uncolonized PDA plug was used as a control. Disease symptoms were observed 2 weeks after inoculation. Brownish, sunken lesions were observed on the base of stems and roots of seedlings inoculated with R. zeae. Stems and roots of uninoculated seedlings were lesion free. Isolates JR-3 and JR-8 were reisolated from plants grown in their respective treatments. This is the first report of R. zeae from Turkey.
