Efficiency of Phage Therapy against Pectobacterium carotovorum that Caused Soft Rot on Potato Tubers

Abstract

Pectobacteriumcarotovorumis the most causal agent of soft rot disease in wide variety of vegetables and crops worldwide. Currently phage therapy used as a safe biological method for controlling plant pathogenic bacteria. Twenty Pcc isolates were obtained from infected potato tubers and soil cultivated with different crops. Pcc isolates identified based on morphological and biochemical characters and confirmed by 16S rRNA gene and identified as Pectobacteriumcarotovorumsubspcarotovorum. Pathogenicity studies revealed that potato tubers were sensitive to soft rottedPectobacterium. Twenty-three bacteriophages specific to the causal agent Pccwere isolated and characterized from potato tubers, soil and sewage samples. Spot and plaque assay techniques were used. The isolated phages were purified for determining the morphology and molecular diversity among phages.The bacteriophages potential prevented biofilm formation of Pccisolates withpercentages of98.5%, 81%, 81.6% and 97%for Pcc1, Pcc2, Pcc3 and Pcc4, respectively.Application of phages cocktail on potato tubers caused a remarkable decrease in soft rot symptoms and disease severity to reach about 7, 15, 17.5 and 15%. However, the efficacy of phages is short longevity on host plants. Formulated phages (phages+ 0.5% corn flour+ 5% sucrose (v/w)) were tested against Pcc on potato tuber for increasing phage longevity at room temperature which achieved a reduction of disease severity to 5, 10, 15, and 13%.

Keywords Soft rot, Pectobacteriumcarotovrounsubsp.carotovorum, phage therapy, bacteriophages.