Emission of volatiles during pathogenic interaction between Erwinia amylovora and Malus domestica

Given that the pathogen-induced plant responses include also changes in volatiles emission (i.e. production of ethylene, NO, methyl jasmonate), the present study aimed to characterize the volatile production by the infected plants. A first characterization of the volatile profiles of infected plants was obtained by proton transfer reaction-mass spectrometry (PTR-MS) which allows the real-time monitoring of the emission. Contemporaneously, the real-time emission of ethylene was monitored by laser-based photoacoustic detector. Successively, the gas chromatographic- mass-spectroscopy (GC-MS) analysis was used for identifying the specific volatiles emitted during the infection development. The characterization of the VOCs emissions showed that specific compounds are produced in response of the pathogen attack. In addition, some of these compounds, such as 2,3-butendiole and hexenal, are known to play a role in the ecological interactions occurring between plant and microbes. Finally, on the basis of the different profiles of VOCs emission by healthy and infected plants, an electronic nose [EOS835 (Sacmi, Imola - Italy)], was challenged for the early diagnosis of fire blight on asymptomatic plant material. In experimental conditions, the electronic-nose successfully discriminated the infected plants, however, its practical application in open fields, nurseries and packing houses still requires further studies.