Changes in volatile production during an infection of potatoes by Erwinia carotovora

The monitoring of volatiles produced by diseased potatoes has been studied as a method of detecting infections in potato storage units. Previous studies attempted to identify pathogen-specific volatiles as markers for the presence of disease, however, consistent results were difficult to obtain. A possible solution is to consider overall qualitative and quantitative changes in the volatile profile over the course of an infection. The objective of this study was to investigate this method of data analysis. The study was done using 1-kg batches of potatoes stored at room temperature in metal canisters fitted with volatile traps containing Chromosorb 105. Either one or all of the potatoes in the batch were inoculated with Erwinia carotovora, the causative agent of soft rot. A canister containing uninoculated healthy potatoes was used as the control. A dynamic headspace sampling method was used to sample periodically the air for volatiles in the experimental and control canisters. The analysis of volatiles was done by gas chromatography. Comparison of the volatile profiles arranged in chronological order showed a progression over time, in the types and amounts of volatiles produced. A wider range of volatiles were produced by infected potatoes than by healthy potatoes. Differences between the volatile profiles of healthy and inoculated potatoes were observed as early as 24 h into the experiment while the total quantity of volatiles produced was initially low and increased exponentially as the infection became well established. The time difference between these two observations was 36-48 h and represented the time in which measures can be taken to contain the infection. The amount of volatile produced was dependent on the initial amount of bacteria, the growth of the bacteria and the detection limits of the Chromosorb and the gas chromatograph. (C) 2001 Elsevier Science Ltd. All rights reserved.