Insights into kiwifruit bud rot

Abstract

Bud rot caused by Pseudomonas syringae pv. actinidiae biovar 3 (Psa) is a severe issue for the kiwifruit industry in New Zealand, particularly within green-fleshed cultivars. Successful management of this disease requires a detailed understanding of the disease cycle, such as identifying when and where Psa is present in/on winter- and flower-buds, the timing of bud-rot initiation, incidence and progression, and any varietal/seasonal/environmental differences. Relevant data is being collected on two green-fleshed cultivars: Actinidia chinensis var. deliciosa ‘Hayward’ and A. chinensis var. chinensis x A. chinensis var. deliciosa ‘Zesh004’ (commonly known as Green14), at four sites where bud rot had been noticed previously. Winter buds are sampled fortnightly and flower buds are sampled weekly from each site. Results from the first year, 2016, indicate that bud-rot incidence was higher in ‘Hayward’ than in Green14. Psa was detected in dormant and sprouted winter buds but its presence was inconsistent. Psa was detected in all parts of dissected ower buds, with the highest incidence in sepals, then in stalks, and gradually lower detection rates in petals, anthers and ovaries respectively.