CHARACTERIZATION OF WAITEA-CIRCINATA (RHIZOCTONIA) ISOLATED FROM AGRICULTURAL SOILS IN ALASKA

A Rhizoctonia similar in morphology to R. oryzae and R. zeae was frequ ently isolated from agricultural soils in south central Alaska during 1983-1990. On potato-dextrose agar, cultures developed white to pale o range mycelium. Sclerotia formed in the agar rather than on the agar s urface, were irregular in shape (similar to those of R. oryzae), and d ark orange to brown when mature (similar to those of R. zeae). Hyphal diameter averaged 6.1 mum and the number of nuclei per cell averaged 5 .4. Radial growth increased from 1.3 mm per 24 hr at 11 C to a maximum of 12.8 mm per 24 hr at 30 C. Most isolates infected barley seedlings . Calculated as percentage of the noninoculated seedling height, virul ence of Alaskan isolates was 49% at 15 C and 48% at 25 C. Among 87 iso lates tested on 2% V8 juice agar or water agar, 7% produced a teleomor ph that was identified as Waitea circinata var. circinata.