Identification of bacteriophages for the biocontrol of the kiwifruit canker phytopathogen Pseudomonas syringae pv. actinidiae

Publisher:
ASM
Publication Type:
Journal Article
Citation:
Applied and Environmental Microbiology, 2014, 80 (7), pp. 2216 - 2228
Issue Date:
2014-01
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Pseudomonas syringae pv. actinidiae is a re-emerging pathogen, which causes bacterial canker of kiwifruit (Actinidia sp.). Since 2008, a global outbreak of P. syringae pv. actinidiae has occurred, and in 2010 this pathogen was detected in New Zealand. The economic impact, and the development of resistance in P. syringae pv. actinidiae and other pathovars against antibiotics and copper sprays, has led to a search for alternative management strategies. We isolated 275 phages, 258 active against P. syringae pv. actinidiae. Extensive host range testing on P. syringae pv. actinidiae, other pseudomonads and bacteria isolated from kiwifruit orchards, showed that most phages have a narrow host range. Twenty four were analyzed by electron microscopy, pulse-field gel electrophoresis and restriction digestion. Their suitability for biocontrol was tested by assessing stability and the absence of lysogeny and transduction. A detailed host-range was performed and phage resistant bacteria were isolated and resistance to other phages examined. The phages were Caudovirales and were analyzed based on morphology and genome size, with representatives of Myoviridae, Podoviridae and Siphoviridae. Twenty one Myoviridae have similar morphology and genome size, yet differ in restriction patterns, host range and resistance, indicating a closely related group. Nine of these Myoviridae were sequenced and each was unique. The most closely related sequenced phages were a group infecting Pseudomonas aeruginosa and characterized by JG004 and PAK_P1. In summary, this study reports the isolation and characterization of P. syringae pv. actinidiae phages and provides a framework for the intelligent formulation of phage biocontrol agents against kiwifruit bacterial canker.
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