Pseudomonas syringae pv. actinidiae survival in point-inoculated kiwifruit vines
The survival and spread over time of Pseudomonas syringae pv. actinidiae (Psa) in point-inoculated kiwifruit vines is poorly understood. Forty-eight 2-year-old vines of Actinidia chinensis var. deliciosa ‘Hayward’ and A. chinensis var. chinensis ‘Hort16A’ were inoculated 30 cm above the crown, either during the active growth (autumn) or dormant (winter) period in two successive years. Vines were cultivated for 3—4 years, after which bacterial isolations were made at intervals along the vines from crown to tip. Psa was found up to 220 cm above the inoculation point and in some of the crowns, 30 cm below the inoculation point. The sites where Psa was found within vines were not always contiguous. Fewer vines of ‘Hayward’ developed serious symptoms or died than ‘Hort16A’; however, more surviving vines of ‘Hayward’ were Psa-positive than those of ‘Hort16A’. Psa was able to survive for at least 4 years in apparently healthy kiwifruit vines. This has implications for the movement of asymptomatic budwood to areas without Psa.