Isolation and characterization of bacteriophages that infect Ralstonia solanacearum in Thailand

Ralstonia solanacearum is the causative agent of bacterial wilt disease in many important crops in Thailand. The pathogen can survive in soil for a long period and has a broad host range. Disease management is still ineffective, and host resistance is limited. Bacteriophage control of R. solanacearum is an alternative method to reduce damage from bacterial wilt disease. The aim of this study was to isolate and characterize bacteriophages that specifically infect strains of R. solanacearum in Thailand and evaluate the potential of bacteriophages as a means of biocontrol of bacterial wilt disease. Thirty R. solanacearum phages were isolated from tomato and pepper fields in various production areas and characterized using electron microscopy, pulsed-field gel electrophoresis and determination of host range. We found 18 podoviruses, eight myoviruses, three siphoviruses and one inovirus that infected R. solanacearum. The phage genome sizes differed considerably (7-300 kbp). The phage host ranges varied from two to 25 of the 32 strains of R. solanacearum tested. Bacteriophages that have wide host ranges and strong lytic activities would be promising agents for biocontrol of bacterial wilt disease in tomato.