DETECTION OF VOLATILE ORGANIC COMPOUNDS FOR THE EARLY DIAGNOSIS OF FIRE BLIGHT ON ASYMPTOMATIC PLANT MATERIAL

DNA-based protocols are the golden standard for the diagnosis of infected plant material. Nevertheless, these methods are time-consuming and require trained personnel, with an efficacy depending on the sampling procedure. Given that plant responses induced by pathogens also include changes in emission of volatiles, the electronic-nose may represent a sensitive, accurate and operator-friendly alternative for rapid and reliable screening of asymptomatic plant material. In comparison with DNA-based diagnosis, which is hampered by the sampling procedure of the plant material, volatiles-based diagnosis can be performed on the whole plant. In the present study, the analysis of volatile compounds is used for the discrimination of two apple diseases: fire blight (Erwinia amylovora) and blossom blight (Pseudomonas syringae pv. syringae) on propagation material. The profile of volatiles emission was initially performed by gas chromatography-mass spectroscopy (GC-MS), proton-transfer time of flight mass spectroscopy (PTR-TOF-MS) to identify possible marker compounds. In addition, two different electronic noses, EOS507 (Sacmi Scrl, Imola, Italy) and PEN3 (Airsense Analytics GmbH, Schwering, Germany), both based on metal oxide semiconductors, were used for diagnosis. After the method validation on in vitro micropropagated plants, a sampling protocol was developed to scale up the diagnosis to real nursery conditions on cold-stored, asymptomatic dormant scions. Electronic-nose can be successfully used in practical conditions, such as nurseries or customs, to screen large quantity of asymptomatic plant material in order precisely steer molecular diagnosis