## 4 Materials and Methods
### Hs-Spm-GcXGC-TOF-MS Analysis  
The sesquiterpene profile of 30-day-old _A. thaliana_ grown on a nootkatone-containing medium was analyzed by multidimensional gas chromatography (GC) coupled with a time-of-flight mass spectrometer (TOF-MS). All plants were grown directly in 20-mL headspace vials to avoid a loss of volatiles. A CTC Combi PAL-xt autosampler (CTC Analytics, Zwingen, BL, Switzerland, CHE) with a heatable agitator and a solid-phase microextraction (SPME) fiber-conditioning station was used to extract the volatiles emitted by _A. thaliana_ from the headspace. The SPME extraction conditions were based on a method previously described [52]. The samples were first heated at 45 \({}^{\circ}\)C for 10 min without stirring. Subsequently, a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS, 50/30 \(\upmu\)m, Stableflex (2 cm) 24 Ga) SPME fiber from Supelco (Bellefonte, PA, USA) was exposed in the headspace of _A. thaliana_ for 30 min. The volatiles were desorbed in the GC inlet at 250 \({}^{\circ}\)C for 5 min. After each desorption process, the fiber was reconditioned at 250 \({}^{\circ}\)C for 15 min to avoid carryover. In addition, an empty headspace vial was measured between each sample as a control, and no sample carryover was detected. Extraction at room temperature directly from the tray produced the same qualitative results but with lower peak intensities. A 7890B gas chromatograph (Agilent Technologies, Bellefonte, PA, USA) interfaced with a Zoex ZX2 GC\(\times\)GC cryogenic modulator (Zoex Corp., Houston, TX, USA) and a Bench TOF-Select(tm) time-of-flight mass spectrometer (Markes International Limited, Llantrisant, Wales, UK) were used to perform the GC\(\times\)GC-TOF-MS measurements. The instrument was fitted with a two-dimensional column set consisting of a highly polar DB-WAX ultra-inert (poly(ethylene glycol); 30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m (length \(\times\) internal diameter \(\times\) film thickness); Agilent Technologies, Bellefonte, PA, USA) as the first dimension (\({}^{1}\)D) column and a moderately polar MEGA-17 MS FAST (poly(50%-phenyl-50%-methylsiloxane); 1.7 m \(\times\) 0.10 mm \(\times\) 0.10 \(\upmu\)m; MEGA s.n.c., Legnano, Milan, Italy) as the second dimension (\({}^{2}\)D) column. Helium was used as carrier gas at a constant flow rate of 1 mL min\({}^{-1}\). The \({}^{1}\)D column was initiated at 35 \({}^{\circ}\)C (5 min hold), then heated at 5 \({}^{\circ}\)C min\({}^{-1}\) to 120 \({}^{\circ}\)C (0-min hold) and, finally, to 220 \({}^{\circ}\)C at 3 \({}^{\circ}\)C min\({}^{-1}\) (5 min hold). The modulator was heated with a +25 \({}^{\circ}\)C offset. The modulation time was 5 s with a 350-ms pulse length. The MS transfer line and ion source were maintained at 250 \({}^{\circ}\)C. Mass spectrometric parameters were as follows: ionization energy \(-\)70 eV, scan speed 100 Hz, recorded mass range 35-250 \(m\)/z and detector voltage \(-\)2222 V. GC\(\times\)GC-TOF-MS data were collected in ProtoTof (Markes International Limited, Llantrisant, Wales, UK; version 2.0) and processed with ChromSpace (Markes International Limited, Llantrisant, Wales, UK; version 1.5). Data was evaluated as a contour plot of the total ion chromatograms (TIC) obtained in the first (\({}^{1}\)D) and secondary (\({}^{2}\)D) dimensions. Analytes were identified based on matching the mass spectrum to a library spectrum, similarity in a retention index and comparison to available authentic reference compounds. The results obtained were confirmed by measuring 3 biological replicates and 3 technical replicates each. Supplementary Materials: Supplementary materials can be found at [[http://www.mdpi.com/1422-0067/21/24/9627/s1](http://www.mdpi.com/1422-0067/21/24/9627/s1)]([http://www.mdpi.com/1422-0067/21/24/9627/s1](http://www.mdpi.com/1422-0067/21/24/9627/s1)): Figure S1. In vitro effect of nootkatone on mortality of _Heterodera schachtii_ [2s, Figure S2. Sesquiterpene hydrocarbons found in the headspace of a 30 days old _Arabidopsis thaliana_, Figure S3.