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Magreola, Nicholas Olatunji (1984) A comparative study of certain soil-borne cereal pathogens with reference to carbohydrate utilisation and polysaccharide hydrolysis. Doctoral thesis, Polytechnic of North London.
Cochliobolus sativus, Fusarium culmorum and Gaeumannomyces graminis var tritici isolates produced pectin degrading enzymes, xylanase and carboxymethylcellulase when grown in a salts medium with an appropriate carbon source. There was little difference in the amounts of enzymes produced by the organisms except for the greatly enhanced endo-poly-rnethylgalacturonase activity when F. culmorum was grown with citrus pectin as the carbon source. When grown on powdered wheat straw xylanase and carboxymethylcellulase activities were not present until the late stages of incubation whereas pectin degrading enzyme activity appeared at an early stage. Absence of phosphate from culture medium did not prevent the production of pectin degrading enzymes by F. culmorum and C. sativus although its presence influenced early enzyme production. Low nitrate concentrations did not preclude cell wall polysaccharide degrading enzymes production. Multiple forms of pectin degrading enzymes were produced by F.culmorum and C. sativus when grown on citrus pectin and and sodium polypectate.
Uptake of glucose from the culture medium by F culmorum was fastest, C. sativus was slowest and G. graminis var tritici was intermediate irrespective of nitrate concentrations. Low levels of nitrate in culture medium drastically reduced the uptake of glucose by C. sativus: slightly reduced that of G. graminis var tritici isolates but increased rate of uptake by F. culmorum.
It is suggested that degradation of pectin and xylan and the utilisation of the degradation product may be as important as cellulolysis in the saprophytic survival of these organisms.
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