Co-Authors:
Dor, E., Weed Research Dept., Newe Ya'ar Research Center, ARO, Israel, Weed Research Dept., Newe Ya'ar Research Center, Agricultural Research Organization, PO Box 1021, Ramat Yishay 30095, Israel
Evidente, A., Dipartimento di Scienze del Suolo, Della Pianta, dell'Ambiente e Delle Produzioni Animali, Università di Napoli Federico II, Portici, Napoli, Italy
Amalfitano, C., Dipartimento di Scienze del Suolo, Della Pianta, dell'Ambiente e Delle Produzioni Animali, Università di Napoli Federico II, Portici, Napoli, Italy
Agrelli, D., Dipartimento di Scienze del Suolo, Della Pianta, dell'Ambiente e Delle Produzioni Animali, Università di Napoli Federico II, Portici, Napoli, Italy
Hershenhorn, J., Weed Research Dept., Newe Ya'ar Research Center, ARO, Israel
Abstract:
The influence of different combinations of illumination and shaking on the growth dynamics, pathogenicity and toxin production of the fungus Fusarium oxysporum f. sp. orthoceras, a biocontrol agent of Orobanche cumana, was studied. The fastest biomass accumulation was obtained under shaking, with or without illumination, with the highest biomass obtained after 3-4 weeks of growth. The biological activity of chloroform extracts of the culture filtrate was characterised: it contained at least two main toxic metabolites that caused necrosis and wilting of various plants and led to mortality of germinating seeds of O. cernua, O. aegyptiaca, O. ramosa and O. cumana. The highest toxic activity of the chloroform extract was obtained under illumination without shaking after 3-4 weeks of growth. The two toxic metabolites were purified and identified as fusaric acid (FA) and 9,10-dehydrofusaric acid (DFA). Both FA and DFA production began in the first week of growth, increasing gradually to their maxima after 4 weeks. The highest level of pathogenic activity of the fungus was obtained after three or more weeks of fungal growth. It can be concluded that in order to produce high levels of toxin and pathogenic activity, the fungus should be grown under illumination without shaking for 4 weeks. © 2007 The Authors.
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