Stimulation of sclerotial germination ofSclerotium cepivorum by host-plant extract |
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Authors: | M A Elnaghy A H Moubasher S E Megala |
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Institution: | (1) Botany Department, Faculty of Science, Assiut University, Assiut, Egypt, U.A.R. |
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Abstract: | Summary Extract from onion bulbs and diffusate from roots of onion seedlings were fractionated by column chromatography. The stimulatory
effects of the different fractions of onion extract on sclerotial germination ofSclerotium cepivorum were studied. The sugar fraction was the most stimulatory, whereas, the amino acid fraction was not effective. Paper chromatographic
analysis revealed the presence of glucose, fructose and no amino acids in the root diffusate. These two sugars and 13 amino
acids were identified in the onion extract. When various sugars and amino acids were supplied individually to autoclaved soil,
only glucose, fructose, mannose and maltose effectively induced sclerotial germination. Partial stimulation occured in nonsterile
soil amended with high glucose concentrations.
Studies on the antibiotic effect of the different fractions against some soil fungi by the spore germination method showed
that, the sugar fraction inhibits completely the spore germination of all the fungi, tested, whereas, the amino acid fraction
was non-inhibitory. Both fractions did not show antibiotic activity when tested by the filter paper disc method.
Attempts to extract inhibitory substances from soil which inhibit sclerotial germination were unsuccessful.
It was suggested that onion extract plays a twofold role in stimulating sclerotial germination in natural soil: (a) a direct
nutritional influence; (b) an antibiotic effect on soil mycoflora which reduces competition for nutrients. |
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