Controlling Damping - Off Disease on Cotton Seedlings Caused by Rhizoctonia solani and Fusarium oxysporum Via Plant Growth-Promoting Rhizobacteria (PGPR)

Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that can be enhance the growth of plant directly or indirectly. These bacteria are commonlyfound in soil associated with roots of plants. Two strains as: Bradyrhizobium japonicum PP236808 and Bacillus subtilis PP250150 have recorded to increase soyabean plant growth directly. In this study, cotton plays an important role in crop rotation with soybean and maize. So that, aim of this study was to enhance the growth of cotton indirectly. The indirect mechanisms involve the biological control for plant pathogens. In vitro, both bacterial strainsexhibited antagonisticFusarium oxysporum and Rhizoctonia solani causes the cotton damping-off disease through the production of lytic enzymes, IAA, hydrogen cyanide, catalase, ammonia and siderophore. Both strains were positive for phosphate solubilization , IAA production, HCN production and also, were found to be catalase positive. While, Bradyrhizobium japonicum PP236808 was highly ammonium. The competition for nutrients leds to improve significantly plant health and promote growth of cotton and consequently seedling survival. Untreated seeds were involved as a control. In greenhouse experiment the treatment of the antagonistic strains (PGPR) significantly repressed the disease incidence to the lowest values as compared to the untreated ones. Also, under field conditions the same PGPR strains significantly decreased the disease incidence. Finally, the application of Bradyrhizobium japonicum PP236808 and Bacillus subtilis PP250150 as bio-controllar significantly increased seed cotton yield. Since, PGPR are environmentally friendly it is safe to be applied for improving growth of plants and increase yield of crops.