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Introduction
Fusarium oxysporum (Fox) is a well‐known pathogen of agricultural and ornamental crops (Nelson et al., 1981). Phytopathogenic strains of Fox are responsible for yield loss of many economically important crops worldwide. For example, wilt of tomato caused by Fusarium oxysporum f.sp. lycopersici (Fol) and foot and root rot of tomato caused by Fusarium oxysporum f.sp. radicis‐lycopersici (Forl) have been reported in at least 32 countries (Jones et al., 1991). These diseases occur both in greenhouse and field and result in significant crop losses (Hahn, 2002; Cai et al., 2003). Root and stem rot of cucumber, caused by Fusarium oxysporum f. sp. radicis‐cucumerinum (Forc), also significantly reduce yield in greenhouses in many countries (Vakalounakis et al., 2004). Besides yield decreases, many Fusarium sp. strains produce toxins which can accumulate in the end products and therefore may become dangerous for human and animal health (Pitt, 2000).
Fox is a cosmopolitan species whose representatives can survive as saprophytes in soil (Burgess, 1981). Due to their ability to utilize a large variety of nutrients, both pathogenic and non‐pathogenic Fox strains can colonize the rhizospheres of various plants and, moreover, enter into the endophytic stage (Garret, 1970). Some non‐pathogenic strains of Fox have been shown to control tomato foot and root rot (TFRR) caused by Forl (Olivain and Alabouvette, 1999; Bolwerk et al., 2005). Moreover ‘BioFox C’, a product based on a non‐pathogenic strain of Fox, is used for the protection of basil, carnation, cyclamen and tomato against pathogenic Fox and Fusarium moniliforme (Jones and Burges, 1998).
Monitoring of plant pathogens is crucial for disease management. Early detection, identification and quantification of the infestation level can help to choose appropriate defence measures. Monitoring of a phytopathogenic microorganism can be done indirectly by following disease symptoms appearing on the plants or by analysing volatiles excreted during pathogen multiplication (Prithiviraj et al., 2004). Direct approaches, such a dilution plating of infested plant or soil on selective media (Vujanovic et al., 2002), detection of fungal spores in plant material (Hahn, 2002), immunological and molecular detection of...