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Developmental Changes in Sclerotia of the Rice Sheath Blight Fungus. Teruyoshi Hashiba, Hokuriku National Agricultural Experiment Station, Joetsu, Niigata Ken, Japan; Shizuo Mogi, Hokuriku National Agricultural Experiment Station, Joetsu, Niigata Ken, Japan. Phytopathology 65:159-162. Accepted for publication 2 August 1974. DOI: 10.1094/Phyto-65-159.

Sclerotia of the sheath blight fungus, Rhizoctonia solani of rice plant at early stages of development are composed of compact masses of hyphal cells about 5 µm wide and cell wall thickness is about 0.09 µm. The size of sclerotia increases after initiation of sclerotia and becomes maximum after about 30 hours, coincident with the start of pigmentation. At this stage, the cells of the outer layer start to empty. Widths of the cells in the central mass increase rapidly to about 15 µm until browning is completed at about 40 hours. With increasing age, cell wall thickness increases. Initially the sclerotia are dense and sink in water; within 15 days, cell contents of the outer layer decrease and the sclerotia become buoyant in water. Cell wall thickness of the 15-day-old sclerotia are about 0.51 µm. At this stage, there is a well-defined layer of living cells in the center, surrounded by an outer layer of empty cells.

Additional keywords: differentiation, morphology, Rhizoctonia solani.