Strains of bacteria Dickeya fangzhongdai cause soft-rot disease, which is responsible for high economic loss in commercial production of orchids in Slovenia. One of the disease control options is the bacteriophage BF25/12, which specifically infects some of the strains of D. fangzhongdai and could therefore be used to control soft-rot in orchids. Before the bacteriophage can be used in practice, the interactions with the host bacterium under different environmental conditions such as pH, UV radiation and temperature need to be studied. The aim of this master thesis was to investigate the effect of temperature on the interaction between D. fangzhongdai and bacteriophage BF25/12. The study was conducted by plaque assay, adsorption test and by monitoring bacterial growth in liquid media in the presence of bacteriophage. Strains B16, MK7 and JS5T were found to be more susceptible to bacteriophage infection at lower temperatures (20 and 28 °C) than at higher temperatures (37 and 42 °C). In addition, it was found that more bacteriophages were adsorbed on the surface of D. fangzhongdai B16 at 28 °C than at 37 °C. By monitoring the bacterial growth, the differences in infection kinetics between different D. fangzhongdai strains at different temperatures were observed. At 28 °C, strains B16 and MK7 were sensitive, strain JS5T was moderately sensitive, and strains S1 and NCPPB 3274 were insensitive to bacteriophage infection. Howevert, at 37 °C, all five strains were insensitive to infection. It is concluded that bacteriophage BF25/12 has potential application for orchid disease control at 28 °C, but the possibility of bacterial resistance should be considered.
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