Induction of Systemic Resistance (ISR) against Fusarium oxysporum f. sp. radiciscucumerinum on Cucumber by Isolates of Trichoderma and Fluorescent Pseudomonads from Cucumber Rhizosphere

Fusarium stem and root rot disease caused by Fusarium oxysporum f. sp. radicis cucumerinum is an important disease in cucumbers. Induced systemic resistance (ISR) by Trichoderma and Fluorescent Pseudomonads is a promising method for biocontrol of this disease. Twenty isolates of Trichoderma and 20 isolates of fluorescent Pseudomonads were isolated from cucumber rhizosphere by Macfaden-Saten and S1 selective media respectively. Spilt root system was used for screening these isolates for induction of systemic resistance against this disease. The experiment was performed with 42 treatments including positive and negative control and nine replicates. After four weeks, the disease was evaluated by scoring the plants and the disease incidence for each treatment was estimated. The result, showed that Ps9, Ps14, Ps12, and Ps6 isolates of Pseudomonads and Tr6 and Tr9 isolates of Trichoderma with disease indices 34.4, 34.4, 43.8, 46.9, 12.5 and 12.5%, respectively, reduced the disease incidence significantly compared with control. During the experiment pathogen and antagonists were separate from each other and the control of the disease was due to a plant mediated phenomena which seems to be induced systemic resistance. The results are promising in applying these biocontrol agents for control of this disease.