Selection of virulent bacteriophages for biological control of plant bacterioses caused by Ralstonia Solanacearum

Ralstonia solanacearum is among the most dangerous phytopathogens globally, causing significant economic losses by infecting major crops such as potatoes, tomatoes, bananas, and others. Its persistence in soil and water, coupled with genetic variability, complicates control measures using antibiotics and chemical pesticides. Therefore, it is crucial to develop effective and environmentally safe control methods for agriculture. The main goal of the presented research is to characterize specific phages against R. solanacearum and assess their potential for biological control of plant bacterial diseases. We studed basic biochemical characteristics for 40 isolates of R.solanacearum, as a result, it was revealed that all the isolates were similar to the typical strain of R. solanacearum by biochemical characteristics. Subsequently, we evaluated the sensitivity of these isolates to 10 different antibiotics. It was determined that R. solanacearum strains were resistante to these antibiotics: cefazolin 100%, ampicillin 97.5%, polymyxin 97.5%, gentamicin 95%, kanamycin 92.5%, streptomycin 92.5%. These data reinforce the necessity for more effective means to combat the bacteria. We also studied the virion morphology of seven bacteriophages specific to R. solanacearum by electron microscopy. The phages belong to the Myoviridae and Podoviridae families. The subsequent objective was to assess the lytic activity of phages specific to R. solanacearum, which revealed that 31 out of 40 strains were lysed by a combination of seven bacteriophages. Restriction profile comparison allowed us to look at the genetic diversity of the study phages. Five different types of phages have been isolated. Based on these results, three phages (R.s 3-1; R.s 6-3; R.s 4) specific to R. solanacearum were selected for further research. We studied the influence of physical and chemical factors on the selected phages, it was determined that these phages are characterized by stability at high temperature and different pH environments. Additionally, the selected phages maintained stability in liquid media for 24 hours at dilutions of 10 to the power of -1,10 to the power of -2,10 to the power of -3. From the obtained results, we can conclude that the broad lytic spectrum, long-term lysis stability in the liquid media, resistance to physical-chemical factors of the three selected R. solanacearum-specific phages meet the requirements for bacteriophages used in biological control.

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