Relationship between Botrytis cinerea inoculum in kiwi fruit vines, contamination of the fruit surface at harvest and stem end rot in cool storage

Stem end rot of kiwifruit caused by Botrytis cinerea has been responsible for significant postharvest fruit losses. It was hypothesized that B. cinerea contamination of the fruit surface was a significant source of inoculum for fruit infection at harvest. Relationships between B. cinerea populations (Range = 1 x 10(3) to 1 x 10(6) spores per fruit) artificially applied to fruit surfaces at harvest, contamination of the picking wound and stem end rot were investigated in 1994. The incidence of stem end rot ranged from 0-44% and was highly significantly correlated with both the number of viable B. cinerea propagules on the fruit surface and B. cinerea contamination of the picking wound. In a separate study in 1994, the size of B. cinerea populations in experimental plots was manipulated. significantly fewer viable B. cinerea propagules on the fruit surface at significantly less stem end rot in low inoculum treated plots compared to high inoculum treated plots. We conclude that B. cinerea inoculum from necrotic tissues in the canopy collects on the hairy external surfaces of kiwifruit. During harvest operations these propagules are transferred to the picking wounds and if conditions are conducive, will infect fruit and cause stem end rot.