Lysis activity of bacteriophages isolated from sewage against Ralstonia solanacearum and Erwinia chrysanthemi

Two groups of bacteriophages (phages), one forming a clear plaque , and the other forming turbid plaque with a small holo zone in the middle were isolated from sewage using three different strains of Escherichia coli (TG1, ER2738 and BL21) as a host. All the phages were subjected to lysis study against phytopathogen bacterial wilt Ralstonia solanacearum and heart rot Erwinia chrysanthemi. These phages have very restricted host range and the application as an alternative biocontrol agent has recently gained wide interest. Thus, the present study was aimed to isolate novel phages against R. solanacearum and E. chrysanthemi, and to further evaluate their lytic characteristics. A total of 132 isolates of phages were obtained from sewage samples. Three phages (P45, P71 and P631) showed potential to lyse R. solanacearum with clear zone ratios of 3.34,3.00 and 3.06 respectively. Only P62l formed a clear zone ratio of 3.26 against E. chrysanthemi. The other phages did not show any significant lysis activity. Even though these phages showed some promising results, more studies are needed to investigate the effectiveness of phage on the crop plants. Introduction The bacterial Ralstonia solanacearum (Yabuuchi et through the roots and