Thermo desorption unit

O. maius was grown at 25°C in plastic (6 replicates) and glass (3 replicates) petri plates containing MS medium covered with cellophane membranes. VOCs were collected in the cultures headspace after 15 and 30 days from fungal inoculum. Control plates without mycelium were sampled for background correction. VOCs were collected for 6 h from sealed Petri dishes by headspace sorptive extraction using the stir bar sorptive extraction method with Gerstel Twisters (Gerstel GmbH & Co. KG, Mülheim an der Ruhr, Germany) as described in [33 (link)]. The samples were analysed with a thermo-desorption unit (Gerstel GmbH & Co) coupled to a gas chromatograph-mass spectrometer (GC-MS; GC model: 7890A; MS model: 5975C; Agilent Technologies, Santa Clara, CA, USA) as described in [34 (link)]. The chromatograms were analyzed by the enhanced ChemStation software (MSD ChemStation E.02.01.1177, 1989–2010 Agilent Technologies, Santa Clara, CA, USA). The TIC (Total Inorganic Carbon) of each VOC in the final dataset was recalculated from the absolute abundance of the first representative m/z to eliminate noise. The calibration was done as described in [34 (link)]. The emission rates were calculated on fungal mycelium area (pmol cm^-2 h^-1) bases.

Tenax TA sorbent tube was conditioned at 315 °C for 1 h in TDS Tube Conditioner (Gerstel). Two milliliters of the sample were dosed into a 20 mL headspace vial which contains 2 g of NaCl. Before the sampling, 25 μl of 2-octanol solution (2 mg/L in ethanol) was added as internal standard. DHS sampling was carried out with Gerstel MPS2 auto-sampler (Mülheimander Ruhr, Germany), including the sampling, thermal desorption (ThermoDesorption Unit, Gerstel) and cryo focusing (Cooling Injection System, Gerstel). Detailed experimental parameters are listed in Table S 2.