Bacteriophage Control of Pseudomonas savastanoi pv. glycinea in Soybean

Bacterial viruses (bacteriophages) have been considered as potential agents for the biological control of bacterial phytopathogens due to their safety and host specificity. Pseudomonas savastanoi pv. glycinea (Psg) is a causative agent of the bacterial spotting of soybean (Glycine max Willd). The harm caused by this bacterium to crop production and the development of antibiotic resistance in Psg and other pathogenic microorganisms has led to the pursuit of alternative management strategies. In this study, three Psg-specific lytic bacteriophages were isolated from soybean field soil in geographically distant regions of Russia, and their potential for protective action on plants was assessed. Sequencing of phage genomes has revealed their close relatedness and attribution to the genus Ghunavirus, subfamily Studiervirinae, family Autographiviridae. Extensive testing of the biological properties of P421, the representative of the isolated phage group, has demonstrated a relatively broad host range covering closely related Pseudomonas species and stability over wide temperature (4–40 °C) and pH (pH 4–7) ranges, as well as stability under ultraviolet irradiation for 30 min. Application of the phages to prevent, and treat, Psg infection of soybean plants confirms that they are promising as biocontrol agents.