Study of possibility of biological control of charcoal rot on melon (Macrophomina phaseolina) by Pseudomonas fluorescens isolates

To study of biological control of charcoal rot of melon caused by Macrophomina phaseolina، 187 isolates of fluorescens pseudomonas isolated of rhizosphere and soil of melon plants. Then 12 isolates belong to I، III and V biovars of P. fluorescens and B biovar of P. putida were selected for greenhouse experiments based on inhibition amount. Pseudomonas isolates inhibited mycelial growth significantly of M. phaseolina in Dual culture، volatile and culture filtrates test. Percentage of growth inhibition in Dual culture test was by 17. 9 to 72. 2% in Volatile test 7. 1 to 71. 5% and in culture filtrates 19 to 91. 9% for fungus isolates. Mycelial growth of M. phaseolina decreased by all of the pseudomonas isolates according to siderophore production test. Greenhouse experiments were made by seedcoating and soil methods. The results of greenhouse experiments in soil and seed treatments showed that when soil of pots inoculated with pseudomonas، percentage of healthy plants were significantly greater than in those of pathogen control (p< 0. 05). Isolates P6، P5 (P. fluorescens biov III) and P3 (P. putiada biov B) caused less incidence of disease.