Biological control of Fusarium oxysporum f.sp. lycopersici by antagonistic bacteria Bacillus and Pseudomonas isolated from tomato rhizosphere in Lorestan province

Fusariumwilt of tomato is a worldwide disease causing significant damage in more than 32 countries. In this experiment the antagonistic effects of locally isolated strains of Bacillus subtilis and Pseudomonas fluorescens against the pathogen were studied in the laboratory and greenhouse. Results showed that in dual culture tests the isolates P. fluorescens (P1), P. fluorescens (P2) and Bacillus subtilis inhibited growth of Fusarium by 28/8, 25/74 and 10/52 percent respectively. In the greenhouse experiments roots of tomato seedlings were separately dipped in the bacterial suspensions before transplanting into pots, the top one-third soil of which was inoculated with the pathogen. The interaction between antagonists and pathogen in the greenhouse, 60 days after inoculation of seedlings was evaluated by measurement of growth factors, root and shoot wet and dry weights, of tomato plants and the severity of Fusarium wilt disease. Both P. fluorescens and B. subtilis decreased disease incidence and increased growth factors of tomato plants in the presence of the pathogenic fungus but, in contrast to results of dual culture tests, Bacillus subtilis was more effective in reducing disease severity.