DIVERSITY OF BACTERIOPHAGES INFECTING PECTOBACTERIUM FROM POTATO FIELDS

Abstract

Bacteria belonging to the genus Pectobacterium are causal agents of soft rot disease in diverse crops including potato. This disease is very difficult to control and no promising methods have been developed. The use of phage therapy has been suggested to control bacterial diseases; however, this method has not been applied widely because of its unreliability to the plant environment and the narrow spectrum of activity intrinsic to phages. This study identified bacteriophages capable of lysing diverse Pectobacterium species and isolates from plant and soil samples obtained from the potato rhizosphere. Repeated pickings of plaque resulted in the isolation of 189 single phages showing a diverse spectrum of host specificity. From these, 24 core phages were selected and a dendrogram was generated. A phylogenetic tree was also generated with the DNA fingerprints confirming the genetic diversity of the selected phages. The results of the phylogenetic tree almost fit those of the dendrogram. The stability of the selected phages was investigated under various temperatures and pH conditions in vitro. The phages were stable at 16°C-40°C and pH 6-7. Moreover, the viability of the phages differed significantly depending on the phage samples selected. Morphological characterization of the selected phages showed that they could be classified into three different groups, Podoviridae, Myoviridae, and Siphoviridae with diverse head sizes and tail lengths. These results are expected to contribute to controlling the disease, but further investigations of the genetic and molecular aspects will facilitate a better understanding of phage and bacteria interaction.