Infection of ZESPRI GOLD kiwifruit (<i>Actinidia chinensis</i> Hort16A) lenticels by <i>Pseudomonas syringae</i> pv <i>actinidiae</i>

Abstract

Pseudomonas syringae pv actinidiae (Psa) is a bacterium whose virulent form (PsaV) causes severe infections of kiwifruit particularly Actinidia chinensis Hort16A Lenticels on kiwifruit canes function as pores allowing gaseous exchange The lenticellular structure penetrates through the periderm potentially allowing bacterial entry and subsequent cortex infection Bacteria have been observed inside and directly below lenticels from ca 3yearold woody tissue from the field To investigate this pathway of bacterial infection further lenticels from three wood ages were inoculated with a strain of PsaV at 109 cfu/ml Brown staining was observed on lenticels 3 days after inoculation on the youngest wood (< 1 year old) Lenticels were sectioned 2 and 4 weeks after inoculation and isolations were conducted from sterilised tissue after 4 weeks Psa was visible inside lenticels of the youngest wood 2 weeks postinoculation and was also isolated from the youngest tissue after 4 weeks Bacteria were not observed in lenticels of older wood and Psa was not isolated