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Characterization of an Exo-β-1,3-Glucanase Produced by Pichia anomala Strain K, Antagonist of Botrytis cinerea on Apples

April 1998 , Volume 88 , Number  4
Pages  335 - 343

M. Haïssam Jijakli and Philippe Lepoivre

Unité de Phytopathologie, Faculté Universitaire des Sciences Agronomiques, 2, Passage des Déportés, B-5030 Gembloux, Belgium

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Accepted for publication 22 December 1997.

The exo-β-1,3-glucanase (EC activity of Pichia anomala strain K, an antagonistic yeast of Botrytis cinerea on postharvest apples, was studied in a synthetic medium supplemented with laminarin, a cell wall preparation (CWP) of B. cinerea, or glucose. The highest enzyme activity was detected in culture media containing a CWP of B. cinerea as the sole carbon source, whereas the lowest activity was observed in culture media supplemented with glucose. Exoglc1, an exo-β-1,3-glucanase, was purified to homogeneity from culture filtrates of strain K containing a CWP. The molecular mass of exoglc1 was estimated to be under 15 kDa. Optimum activity of exoglc1 was recorded at 50°C and pH 5.5. The exoglc1 Km value was estimated at 22.4 mg/ml. Exoglc1 showed in vitro a stronger inhibitory effect on germ tube growth of B. cinerea than on conidia germination and caused morphological changes such as leakage of cytoplasm and cell swelling. Exo-β-1,3-glucanase activity was detected on apples treated with strain K and was similar to exoglc1 on the basis of activity on native gel. Moreover, the addition of a CWP to a suspension of P. anomala stimulated both in situ exo-β-1,3-glucanase activity and protective activity against the pathogen, strengthening the hypothesis that exo-β-1,3-glucanase activity is one of the mechanisms of action involved in the suppression of B. cinerea by P. anomala strain K.

© 1998 The American Phytopathological Society