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Morphological and cultural characteristics of fungi causing rice sclerotial diseases were examined. Hyphal widths of R. solani and R. oryzae were same and ranged 6.0-12.0㎛ with average 9.0㎛, the widest among those of the sclerotial fungi examined. Hyphal width of R. oryzaesativae ranged 6.0-9.0㎛ with average 7.41㎛. Hyphal width of R. cerealis was the narrowest among those of Rhizoctonia species examined, and the same was hyphal width of S. oryzae among those of Sclerotium species. Nuclear staining by HCL-Giemsa method showed that R. solani and R. oryzae had many nuclei within one hyphal cell, S. oryzae one nucleus, and the other sclerotial fungi mostly two nuclei. The nuclear number of R. solani was the largest, which ranged 2-17 with average 6.3. Average size of sclerotic of the sclerotial fungi except S. hydrophilum and S. oryzae produced in lesions ranged 1.0-2.0㎜. Average size of sclerotic of S. hydrophilum and S. oryzae was 0.5㎜ and 0.24㎜, respectively. Sclerotic of R. solani and R. oryzae produced in culture were more variable in size and larger than those produced in lesions. However, the sclerotial sizes of the other sclerotial fungi produced in culture were almost the same as those produced in lesions. Sclerotial colors of sclerotial fungi produced in lesions were similar to those produced in culture, but sclerotial shapes of some sclerotial fungi exhibited somewhat difference between the sclerotic produced in lesions and in culture. Optimum temperature for mycelial growth of R, cerealis was 23℃, and that of the other scterotial fungi ranged from 27 to 33℃. Maximum temperature for mycelial growth of some sclerotial fungi was as high as 41℃, while that of R. cerealis was as low as 31℃. Minimum temperature for mycelial growth of R. cerealis was 2℃, and that of the other sclerotial fungi ranged from 6 to l0℃.
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