Studies on Cercospora kikuchii (Matsumoto & Tomoyasu) Gardner., a causal agent of purple seed stain on soybean (Glycine max (L.) Merrill)
1994
Wichian Agsiriwaranont
The use of blotter and PDA in isolation of purple seed stain casual agent resulted in equal recovery of Cercospora kikuchii. Seed surface disinfestation with 10 % clorox for 1 minute and incubation for 2-3 days allowed for assay and isolation from seed coat. The morphological characters of C. kikuchii fungus from diseased seed coat were as follows: Conidiophores borne in fascicles, divergent, occasionally many stalk on stroma, yellowish brown to dark at base but paler toward the apex, unbranched, geniculate, prominent, conidial scar present, septate, size 3.5-5.5 * 23.5-408 micro m. Conidia were hyaline, acicular, truncate base, apex tapered, multiseptate (4-25), straight or curved, thickened hilum, size 2.5-7 * 56-462.5 micro m, true chlamydospores present, spherical orange yellow membrane, thickened wall. Growth of C. kikuchii was exellent on soybean seed coat agar (SSCA), V-8 juice agar (V-8A) and carrot leaf decoction agar (CLDA) at temperature 25 and 30 deg C. Under lighting regimen with 12 hr of alternating light and dark, continuous light and continuous dark, the sporulation of C. kikuchii on V-8A produced greatly conidia at 12 hr of alternating light and dark and mycelial growth resulted in equal mycelial develop on all lighting regimen. SK.1 and CM.60 susceptible cultivar soybean plant were inoculated at R2 growth stage gave the highest purple seed stain percentages. Humid weather and susceptible cultivar environmental factor that had revealed in purple seed stain percentage. Generally, C. kikuchii did not affect neither germination nor protein, oil and free fatty acid, (FFA) content.
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