"Identification of volatile markers in potato brown rot and ring rot by combined GC-MS and PTR-MS techniques: study on in vitro and in vivo samples.",
J Agric Food Chem
, vol. 62, pp. 337–347, Jan, 2014.
<p>Ralstonia solanacearum (Rs) and Clavibacter michiganensis subsp. sepedonicus (Cms) are the bacterial causal agents of potato brown and ring rot, respectively, and are included in the A2 list of quarantine pathogens in Europe. Identification by GC-MS analysis of volatile organic compounds from Rs or Cms cultured on different nutrient media was performed. GC-MS and PTR-MS analysis were carried out also on unwounded potato tubers infected with the same pathogens. Infected tubers were produced by experimental inoculations of the plants. In in vitro experiments, Rs or Cms emitted volatile compounds, part of which were specific disease markers of potato (2-propanol and 3-methylbutanoic acid), mainly originating from bacterial metabolism (i.e., amino acid degradation, carbohydrate and fatty acid oxidation). In potato tubers, pathogen metabolism modified the volatile compound pattern emitted from healthy samples. Both bacteria seem to accelerate metabolic processes ongoing in potatoes and, in the case of Rs, disease markers (1-hepten-3-ol, 3,6-dimethyl-3-octanone, 3-ethyl-3-methylpentane, 1-chloroctane, and benzothiazole) were identified.</p>
 "Untargeted metabolomics investigation of volatile compounds involved in the development of apple superficial scald by PTR-ToF-MS",
, Jul, 2014.
<p>The superficial scald is an important physiological disorder affecting apple fruit during postharvest storage. To date, the accumulation, and further oxidation, of α-farnesene was considered as the most probable cause for the development of this physiopathy. In order to perform a more broad investigation, a PTR-ToF–MS (proton transfer reaction—time of flight—mass spectrometry) was employed to monitor the volatile organic compounds (VOCs) production along with the progression of this disorder in fruit of “Granny Smith”, an apple variety known to be highly susceptible to scald. The untargeted metabolite investigation was performed on both skin and pulp, as well as comparing control versus treated tissues with 1-methylcyclopropene (1-MCP), an ethylene competitor widely used to prevent the development of this phenomenon. The rapid and non-destructive analysis of the VOC array carried out by PTR-ToF–MS identified three specific groups of metabolites in the skin, among which the 6-methyl-5-hepten-2-one (MHO) resulted significantly associated with the development of the superficial scald in apple. The results proposed in this work suggest the use of this novel equipment for an on-line monitoring of the VOCs released by the apple during the postharvest storage, as well as to use MHO as a possible biochemical marker for an early detection of the superficial scald symptoms.</p>