Biological control of Fusarium oxysporum f.sp. radicis-cucumerinum, the casual agent of root and stem rot of Cucumis sativus by non-pathogenic Fusarium oxysporum

The aim of this study was to evaluate the ability of non-pathogenic F. oxysporum isolates from suppressive soil in Sri Lanka to control Fusarium root and stem rot of Cucumis sativus L. (cucumber) under greenhouse conditions. Three non-pathogenic F. oxysporum isolates were included in the study. Fusarium isolates were first checked in vitro for pathogenic and antagonistic potential. In greenhouse evaluations, the non-pathogenic F. oxysporum iso- lates were introduced to root system just before the seedlings were replanted in pathogen infested soil. The plants were evaluated for disease development after three weeks. Results of the greenhouse pot experiments revealed that, two non-pathogenic F. oxysporum iso- lates significantly reduced Fusarium root and stem rot incidence. However, combining the non-pathogenic fungal isolates did not enhance the plant protection. These data provide evidence that the non-pathogenic isolates have potential to protect cucumber plants from Fusarium-rot. The most appropriate mechanism of action behind the disease suppression in this system would be suppression of saprophytic growth of the pathogen and depriving a niche rather than direct antagonism.