Heat treatments to kill <i>Pseudomonas syringae</i> pv <i>actinidiae</i> on contaminated pollen

Abstract

Various combinations of heat time and relative humidity (RH) were tested for their ability to kill Pseudomonas syringae pv actinidiae (Psa) the cause of kiwifruit canker on freshly harvested anthers artificially contaminated with this bacterium Pollen viability and Psa survival were tested after treatment Although short durations at high temperatures and high RH did kill Psa these treatments were also lethal to pollen When RH was reduced the time before pollen viability was lost increased but Psa survival was also enhanced The most promising treatment was 35C at a RH of 50 or less at which pollen viability was not affected even after 20 h but Psa did not survive when applied at 10⁶ cfu/ml Modelling suggests that extending the time of treatment would kill higher concentrations of Psa The mechanism for Psa death at 35C is probably by a combination of heat and desiccation