Influence of leaf age of <i>Actinidia</i> cultivars Hayward and Hort16A on infection by <i>Pseudomonas syringae</i> pv <i>actinidiae</i>

Abstract

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 NZV) at a rate of 69 10⁸ 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 23 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