c Pseudomonas syringae pv. actinidiae is a reemerging 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 have led to a search for alternative management strategies. We isolated 275 phages, 258 of which were 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, phage-resistant bacteria were isolated, and resistance to other phages was examined. The phages belonged to the Caudovirales and were analyzed based on morphology and genome size, which showed them to be representatives of Myoviridae, Podoviridae, and Siphoviridae. Twenty-one Myoviridae members have similar morphologies and genome sizes yet differ in restriction patterns, host range, and resistance, indicating a closely related group. Nine of these Myoviridae members were sequenced, and each was unique. The most closely related sequenced phages were a group infecting Pseudomonas aeruginosa and characterized by phages 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.

Pectobacterium wasabiae has a narrow host range, having previously only been associated with Japanese horseradish. However, recent characterisation of Pectobacterium causing soft rotting in New Zealand has identified putative P. wasabiae isolates pathogenic to potato. In this study, phylogenetic reconstruction of acnA and mdh DNA sequences and fluorescent amplified fragment length polymorphisms (fAFLP) were used to confirm the identity of the putative P. wasabiae isolates. Both methods clustered the potato isolates closely with the type strain for P. wasabiae, ICMP9121, and also differentiated them from other plant pathogenic enterobacteria. PCR, DNA hybridisation and hypersensitive response (HR) assays were subsequently used to investigate the presence in P. wasabiae of the type III secretion system (T3SS) as well as other virulence factors known to be involved in development of disease by enterobacteria. Although all P. wasabiae strains appeared to elicit a type III-dependent HR in tobacco, genes associated with the T3SS and the putative virulence factors HecB and DspE could not be detected. Thus, genetic characterisation of P. wasabiae confirmed that it is a naturally occurring pathogen on potato, which does not possess the same suite of virulence factors that are involved in the pathogenicity of other enterobacteria on this host.

In this paper, we present the draft sequences of 18 genetically diverse Pseudomonas strains isolated from kiwifruit plants in New Zealand and overseas, including a number that are currently not fully characterized. These sequences will aid in the diagnosis of Pseudomonas on kiwifruit for future pest management and border security decision-making.

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