Controlling Pseudomonas syringae Causing Halo Blight on Bean Plants Via Biocontrol-Formulated Bacterial Viruses

Bacterial viruses are currently used as a biocontrol agent for bacterial plant disease management. The evaluation of formulated bacteriophages mixed with carriers as a biocontrol agent showed efficacy and reduced disease symptoms (halo blight spots HBS) on the leaves of bean plants caused by Ps. syringae. It was isolated on nutrient agar. The single colonies of Ps. syringae appeared flat and produced fluorescent diffusible pigment on the king 's B medium as well as phylogenetically based on 16s RNA gene 726 bp by PCR. Two formulated bacteria viruses were applied as a biocontrol agent to control HBS disease. A complete randomized design was adapted in two experiments with three replications under greenhouse and open field conditions. The formulated bacteria viruses (skim milk and corn flour) significantly decreased the severity of the disease under greenhouse between 88.8 and 85.3 % and under open field conditions between 74.9 and 62.0 %, in comparison to pure bacteria viruses and copper oxychloride treatments to 83.3 and 76.3% in the greenhouse in addition to 74.9 and 62.0 % in open field respectively. The use of SM and CF for disease control experiments enhanced phage lifetime by up to 120 hours and phage density by Log 1.5 and 1.2 PFU/mL in the greenhouse and open field, correspondingly. The formulated bacteriophages (CF and SM) compared with bacteria viruses and copper oxychloride in a greenhouse and open fields showed the lowest HBS and AUDPC values. These phages may be effectively used to control halo blight disease.