Effect of fungal and bacterial biological agent against bean common blight caused by Xanthomonas axonpodis pv. Phaseoli

The bean common blight caused by Xanthomonas axonpodis pv. phaseoli is one of the most important pathogens of bean, which is a serious problem to produce this crop in western regions of the country. Due to the severe damage of this pathogen, using fungal and bacterial bio-control agents can be as an efficient way to reduce the damage of disease on bean. The aim of this study was to evaluate the controller effects of fungal and bacterial biological agents including Trichoderma harzianum, T. virens, Bacillus subtillis and Pseudomonas fluorescence in laboratory and greenhouse conditions on bacteria of bean common blight.
In order to study the effects of biological agent against Xap, in the first stage, was to investigate the percentage growth inhibition of Xapby biological agents under laboratory conditions. In the next step, the interaction of biological agent and pathogenesis bacteria on bean plant was evaluated in a completely randomized design, four replications and biological agent’s treatments are under the greenhouse conditions. Indices such as root and shoot fresh weight, root and shoot dry weight, height roots and stems of beans and disease severity were measured to analyse the control power of the biological agents.
In laboratory conditions, fungal biological agents of T. harzianum with an average diameter of inhibitor halo of 42 mm and inhibiting 56.67% of the growth had highest controller effect on pathogenesis bacteria. However, in greenhouse conditions, P. fluorescence bacteria had better performance and all plant indices under this treatment showed a significant growth. The combined treatment of P. fleurescence T. virens was the best treatment in this experiment with reducing 79.4% of disease symptoms. Treatments P. fleurescence. harzianum and B. subtillis. fleurescence with amount of 69.6 and 55.9% reduced the symptoms, respectively, and are in following levels.
Discussion and Therefore, the use of biological agents can largely reduce the bean common blight, so that it can be an efficient and environmentally friendly method used.