Bacterial plant pathogens represent a major challenge for agriculture, greatly reducing the yield of agricultural crops used to sustain the nutritional needs of the increasing world population. It is known that all major crops are damaged by at least one major bacterial disease. Control of the vast majority of bacterial plant diseases is still based on classic cultural practices, as there is no effective chemical control available. Implementation of biocontrol measures is hindered by lack of sufficient knowledge. Among the most important plant pathogens are bacteria of genus Dickeya. Bacteria from the genus Dickeya, family Enterobacteriaceae are very aggressive, hemibiotrophic, pectinolytic pathogens that have both a wide geographic distribution and host range. Diverse isolates of the genus Dickeya cause soft-rot in a number of host plants, including economically important crops and ornamental plants. However, until very recently, reports of soft-rot disease caused by the genus Dickeya have been limited to herbaceous plants. Dickeya fangzhongdai is the first Dickeya species reported to infect trees, causing bleeding canker necrosis.

Currently, there is no efficient chemical or biocontrol management strategies implemented to control either of the diseases that Dickeya spp. is causing. However, bacteriophage biocontrol strategies were proposed as a promising option for managing soft-rot of potatoes caused by other Dickeya spp. The use of bacteriophages as control and therapy agents has a long history and several bacteriophages have demonstrated repeated, successful applications in plant disease management. However, challenges remain including resistance development in bacteria and complex dynamics among bacteriophages, bacteria and their environment, which remain largely unexplored. Therefore, an approach integrating different types of analysis is needed to study plant pathogenic bacteria – bacteriophages system as the outcome of their interaction occurs and is dependent on highly changing environmental factors. For example, Dickeya spp. shift their lifestyle from epiphytic to pathogenic in an intricate response to changed environmental factors including temperature, oxygen availability and humidity. Moderate temperature (approximately 30 °C) expedite bacteria to shift to the soft rot disease expression. Additionally, shifts in the environmental pH have a great regulatory role for the Dickeya spp. gene expression during the disease development, as the pH is changing from acidic to alkaline during plant infection. Therefore, Dickeya spp. are not only able to withstand a range of different stressors, including elevated temperatures and relatively broad pH interval, but exploit them for efficient adaptation.

In our previous studies, we have established comprehensively characterised D. fangzhongdai system with well-defined genetic and phenotypic traits. We have also isolated and described first bacteriophage from family Podoviridae active against Dickeya spp., bacteriophage BF25/12. The primary host of the bacteriophage is the novel species D. fangzhongdai. We showed suitability of the bacteriophage BF25/12 as a model bacteriophage for researching bacteria-bacteriophage interactions and its influence on the biocontrol management strategies by comprehensive characterisation of the bacteriophage, including genetic and phenotypic trades, environmental stability and development of molecular methods for tracking.

The specific objectives of this research project are:

• to assess if environmental factors, namely temperature and pH, enable pectinolytic bacteria to avoid bacteriophage infection by influencing bacteria-bacteriophage interaction;
• to determine correlation between enzymatic activity of the bacteriophage tail spike protein and adsorption to bacterial cells at different environmental pressures (temperature and pH).

The proposed research will generate new knowledge of a complex bacteria-bacteriophage-environment interaction system. It will improve our understanding of the role of environmental factors on bacteria-bacteriophage systems and its responses. Therefore, results of the study will be of a great practical importance for fine-tuning bacteriophage biocontrol applications, especially in the field of agriculture and plant health.