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Sporulation and Variation in Size of Conidia and Conidiophores Among Five Isolates of Cercospora kikuchii. C. C. Yeh, Graduate Research Assistant, Department of Plant Pathology, University of Illinois, Urbana 61801. J. B. Sinclair, Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 64:373-374. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-373.

The sporulation of five soybean (Glycine max) seed isolates of Cercospora kikuchii, causal fungus of purple seed stain of soybean—Ck-1 (ATCC 36864), Ck-A, and Ck-B from Illinois, Ck-T from Taiwan, and PS-161 from Indiana—was compared on carrot leaf-decoction agar (CLDA), dead soybean plant tissue agar (DSPT), potato-dextrose agar (PDA), and V-8 juice agar (V-8A) at either alternating 12 hr of light and dark or continuous dark at 25 C. Lighting regimen, type of medium, and source of inoculum (mycelia or mycelia plus conidia) influenced spore production. All isolates produced conidia at 12 hr of alternating light and dark; production was sparse under continuous dark. More spores were produced by all isolates on CLDA, DSPT, and V-8A than on PDA. Conidia production was not significantly different among isolates on all media tested. Conidia and conidiophores of Ck-B were smaller than those of the other four isolates. The sizes of conidia and conidiophores varied within each isolate. It is suggested that inoculum of C. kikuchii for field inoculations be grown on V-8A, DSPT, or CLDA under alternating 12 hr of light and dark at 25 C and that the plates be inoculated by spreading mycelia plus conidia over the agar surface.