Evaluating the relationship between quantified Botrytis cinerea levels in pear fruit at harvest and the Botrytis rot incidence and severity at the end of storage: Towards the development of a Botrytis rot management model

Post-harvest rot of pears is of major concern to the industry. Botrytis cinerea, causal agent of Botrytis rot, is the most important. Earlier studies have shown that there is likely to be a minimum inoculum threshold level required for rot symptom development, and it was thus of important to determine the relationship between inoculum level and eventual decay symptoms. Molecular biology-based detection techniques have made it possible to accurately detect and quantify inoculum levels before visual symptom development, making it possible to investigate this relationship in more detail. The aim of this project was to create a standard curve which correlated the amount of inoculum on artificially inoculated fruit at harvest with eventual decay. A further aim was to determine whether samples collected from a variety of orchards fit into this standard curve

Pear fruit were harvested from orchards and artificially inoculated with a variety of defined spore amounts, or kept uninoculated. Thereafter the B. cinerea inoculum level and decay incidence was measured after different periods of storage. Subsequently the data was analysed to investigate the relationship between spore amount present and eventual decay.

• The selected range of artificial inoculation spore amounts, method of application and conditions selected for incubation resulted in a decay data with high resolution over a large dynamic range.
• The artificial inoculation experiment was representable of natural inoculum measured in
• There was a strong relationship between cinerea DNA content and eventual disease incidence over a large dynamic range.
• The project provides high quality, reproducible data in terms of the relationship between inoculum levels and eventual decay symptoms.

The results provide strong support not only that the inoculum levels in the pear calyx-end can be accurately measured, but also that this measurement provides insight into the eventual decay levels that can be expected after storage, in relation to the level B. cinerea DNA measured in samples.