Chitosan and three Trichoderma spp. to control fusarium crown and root rot of tomato in Jeddah, kingdom Saudi Arabia [electronic resource].

Includes references.

Pathogenicity test using five isolates of Fusarium oxysporum f.sp. radicis - lycopersici (FORL) previously isolated from diseased samples of tomato showing typical symptoms of Fusarimn crown and root rot in winter plantations of tomato in Jeddah district, Saudi Arabia revealed that they were all able to cause damping off symptoms in tomato plants. In this respect FORL (isolate No.2) was the most aggressive one in inducing the disease in tomato plants. The inhibitory effect of chitosan against FORL growth under laboratory conditions was indicated. The inhibitory effect was increased as the concentration of chitosan increased from 0.38 to 6.00 mg/ml (PH 5.5). Chitosan also reduced the conidial germination. Complete inhibition was achieved when chitosan concentrations 3.00 and 6.00 mg/ml were used indicating that chitosan had a fungicidal effect. In greenhouse experiments, tomato seeds and transplants treated with chitosan at 3.00 and 6.00 mg/ml improved the stand of tomato plants grown in soil infested with FORL and significantly reduced both damping off and Fusarimn crown root rot (FCRR) incidence. The highest height, fresh and dry weights of the shoot system and fruit yield were obtained in tomato plants grown from transplants treated with chitosan at 6.00 mg/ml concentration. In vitro studies revealed that all the tested Trichoderma spp. isolates have sharply decreased the mycelial growth of the pathogenic fungus. Data of greenhouse experiments indicated that using any of the three Trichoderma spp. tested caused a significant reduction of FCRR disease incidence in comparison with the check treatment. Tomato transplants treated with T. harzianum before planting in soil artificially infested with FORL resulted in the lowest percentage of disease incidence.

Summary in Arabic.

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