New Zealand Plant Protection 65 (2012): 289
The influence of leaf age on infection by Pseudomonas syringae pv. actinidiae (Psa) was investigated using potted 'Hayward' and 'Hort16A' kiwifruit plants. Leaves were spray inoculated with an isolate of Psa (haplotype NZ-V) at a rate of 6.9 × 108 cfu/ml. Plants were maintained in a saturated environment in a plastic hot house within the confines of a containment laboratory at Plant & Food Research, Mt Albert Research Centre, Auckland. All leaves were assessed for symptoms 8 days after inoculation and thereafter at approximately weekly intervals for 4 weeks. At each assessment, changes in symptom expression on the leaves were recorded. Flecking was evident on some of the leaves 8 days after inoculation. Many of these flecks later became necrotic spots with halos similar to Psa infections that have been observed in the field. A higher percentage of leaves, that were 2-3 weeks of age at inoculation, had flecking and spotting than leaves of other ages. Leaves that were 7 weeks or older did not show any symptoms of infection by Psa. Overall, leaves on 'Hort16A' showed slightly more flecking and spotting than 'Hayward'.
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