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Identification, Virulence, and Distribution of Two Biovars of Pseudomonas syringae pv. actinidiae in New Zealand

June 2013 , Volume 97 , Number  6
Pages  708 - 719

J. L. Vanneste, J. Yu, and D. A. Cornish, The New Zealand Institute for Plant & Food Research Ltd., Hamilton 3240, New Zealand; D. J. Tanner, ZESPRI International Ltd., Mount Maunganui 3149, New Zealand; R. Windner, Kiwifruit Vine Health Inc., Mt Maunganui 3149, New Zealand; J. R. Chapman and R. K. Taylor, Plant Health and Environment Laboratory, Ministry for Primary Industries, Auckland 1140, New Zealand; J. F. Mackay, dnature diagnostics & research Ltd., Gisborne 4010, New Zealand; and S. Dowlut, Verified Laboratory Services, Seeka Kiwifruit Industries, Te Puke, New Zealand

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Accepted for publication 3 November 2012.

Pseudomonas syringae pv. actinidiae, the causal agent of bacterial canker of kiwifruit, was detected for the first time in New Zealand in November 2010. Only in Bay of Plenty, one of the four regions where this pathogen had been detected, did symptoms evolve beyond leaf spots, resulting in cane die-back, wilting of canes, and canker, sometimes leading to death of the vine. Molecular analysis (cts haplotype and BOX-polymerase chain reaction [PCR] electrophoretic pattern) of strains isolated from different regions of New Zealand revealed that two biovars could be distinguished. They have been called biovar 3 and biovar 4 to differentiate them from strains from Japan (biovar 1) or Korea (biovar 2), which have a different cts haplotype or a different BOX-PCR pattern. Biovars 3 and 4 displayed different degrees of virulence, as measured by their ability to cause leaf spots on young, potted kiwifruit plants. Biovar 3, which has also been present in Italy since 2008 and in France, was found in the Bay of Plenty, where cane diebacks were observed. In contrast, no symptoms other than leaf spots have been observed in orchards where strains of biovar 4 have been isolated. We report the distribution and the disease progression of biovars 3 and 4 in New Zealand.

© 2013 The American Phytopathological Society