Evidence for a specific elicitor from culture filtrates of Fusarium oxysporum f. sp. radicis-lycopersici
1996
Heremans, B. (Rijkscentrum voor Landbouwkundig Onderzoek, Merelbeke (Belgium). Station voor Plantenziekten)
The in vitro production of a specific elicitor by Fusarium oxysporum f. sp. radicis-lycopersici (Forl) was investigated by growing Forl in liquid shake cultures with different mineral composition. To test the biological activity of the possible elicitor, cell-free filtrates were injected into leaves of resistant and susceptible tomato cultivars. When Forl was grown in a complete Czapek-Dox medium, non-specific signal molecules were synthesized which induced chlorosis and necrosis in leaves of both resistant and susceptible plants. On the other hand, a specific elicitor was produced and secreted in the medium when the fungus was grown in the presence of limiting amounts of nitrogen. The type of nitrogen source (nitrate, ammonium and glutamine) did not influence the response observed. Limitation of the carbon source did not induce the synthesis of specific elicitor molecules. Possibly the addition of plant factors also stimulates the production of a specific elicitor since elicitor activity is observed when Forl is cultivated in leaf extracts of a susceptible tomato cultivar. Forl produces fysiospecific elicitors since elicitor molecules of F9 induced chlorosis in Trust variety and Lycopersicon pimpinellifolium, but not in Moneymaker. Both Trust and Lycopersicon pimpinellifolium are resistant to the F9-isolate. On the other hand signal molecules of F30 only caused chlorotic and necrotic spots in Lycopersicon pimpinellifolium. Both Moneymaker and Trust are susceptible to the F30-isolate.
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