α phellandrene

The synthetic standards including hexanal, α-thujene, α-pinene, camphene, o-cymene, sabinene, β-pinene, myrcene, α-terpinene, β-terpinene, terpinolene, decanal, tridecane, pentadecane, cedrol, hexadecane and the solvent dichloromethane were purchased from Sigma Aldrich (USA) whilst δ-2-carene, α-phellandrene, δ-3-carene, p-cymene, limonene, β- phellandrene, β-ocimene [mixture of (E) and (Z)], dihydrotagetone, δ-elemene, β-elemene, α-cedrene, (E)-caryophyllene, α-humulene, (E, E)-α-farnesene were purchased from Merck (France) and were used to confirm the identified compounds. The chemical purity of the synthetic standards except for sabinene (75%) and α-phellandrene (85%) ranged between 90–99%.

The GC-MS analysis of the EOs was carried out on an Agilent 6890 gas chromatograph equipped with a fused silica capillary column HP-5MS (30 m × 0.25 mm film, 5% phenylmethyl-siloxane and 0.25 μm). The EOs were dissolved in n-hexane (2 mg/mL). The injection of 1 μL of each sample was carried out in split mode with a ratio of 1:100; helium was used as the carrier gas at a rate of 1 mL/min. The operative conditions were as follows: temperature of injector 250 °C, temperature of detector 280 °C. The oven temperature varied as follows: 35 °C to 325 °C with a rate of 5 °C/min. The equilibration time was 0.5 min. MS operate in electron impact was at a potential of 70 eV in a scan range from 50–550 m/z. The identification of the components was based on their Kovats retention indices and their comparison with those of the literature [38 ,39 ,40 (link),41 (link)], and their mass spectra with those available in the NIST 02 and Wiley 275 mass spectral libraries [63 ]. The Kovats indices were calculated related to a series of n-alkanes (C8–C30). This identification of some components was confirmed by co-injection with authentic compounds: α-pinene, sabinene, α-phellandrene, α-terpinolene, methyl eugenol and β-phellandrene (purchased from Sigma-Aldrich, Germany). Quantification was electronically recorded from FID area data using ChromCard program, Thermoquest.

We used two kinds of plant VOCs: nonanal (96%, Beijing Bingda Biotechnology Co., Ltd., Beijing, China) and α-phellandrene (85%, Sigma, and tomato leaf (mature leaf) (Solanum lycopersicum cv. Shouhefenguan). The plant VOCs were diluted in hexane (5%, v/v), while the tomato leaflets (about 20 mm × 30 mm) were directly used as a control. Fifty newly emerged (one-day-old) male and female adults (sex ratio, 1:1) were placed in a 50 mL centrifuge tube and considered one biological replicate. Two hours later, one piece of filter paper (20 mm × 30 mm) was dripped with 20 μL of diluted plant VOC (nonanal or α-phellandrene) or a tomato leaflet, which was placed in the above centrifuge tube to excite the adults [47 (link),48 ]. Five hours later, the heads of the excited adults were dissected and placed in a 1.5 mL centrifuge tube. In total, 15 samples (3 VOCs/tomato leaf × 5 biological replicates) were collected.

Aromadendrene, Borneol, α-Bisabolol, Camphene, Carvacrol, Caryophyllene oxide, 1,8-Cineole, α-Humulene, Limonene, Linalool, (E)-β-Ocimene, α-Phellandrene, α-Pinene, β-Pinene, Sabinene, α-Terpinene, γ- Terpinene, Terpinen-4-ol, α-Terpineol, α-Thujene, Thymol, soluble starch, DNSA (dinitrosalicylic acid), were purchased from Sigma Aldrich (Milan, Italy). Sodium tartrate, sodium potassium tartrate, sodium acetate were bought from Merck (Darmstadt, Germany).

The following compounds were purchased from Sigma–Aldrich (St. Louis, MO, USA): hexanal (98% chemical purity), (E)-2-hexenal (98% chemical purity), octanal (99% chemical purity), nonanal (95% chemical purity), decanal (≥98% chemical purity), (E)-2-nonenal (97% chemical purity), benzaldehyde (≥99% chemical purity), 6-methyl-5-hepten-2-one (99% chemical purity), 1-hexanol (≥99% chemical purity), (Z)-3-hexen-1-ol (98% chemical purity), 1-octen-3-ol (98% chemical purity), propyl 3-methylbutanoate (≥98% chemical purity), 3-methylbutyl propionate (≥98% chemical purity), 3-methylbutyl 3-methylbutanoate (≥98% chemical purity), hexyl acetate (99% chemical purity), ethyl octanoate (≥99% chemical purity), (Z)-3-hexenyl acetate, (Z)-3-hexenyl 3-methylbutanoate (≥97% chemical purity), α-pinene (98% chemical purity), α-phellandrene (≥95% chemical purity), limonene (≥98% chemical purity), (E)-β-ocimene (≥90% chemical purity), p-cymene (99% chemical purity), linalool (97% chemical purity), α-terpinyl acetate, 2-phenylethyl acetate (99% chemical purity), (E)-geranyl acetone (96% chemical purity), hexane (≥99% chemical purity). Ethyl hexanoate (99% chemical purity), 3-methylbutyl acetate (98% chemical purity) were purchased from Alfa Aesar (Ward Hill, MA, USA), δ-3-cerene from Carl Roth (Karlsruhe, Germany), α-farnesene from Bedoukian Research Inc. (Danbury, CT, USA).

Octan-2-ol (97%), 1-hexanol (99%), cis-3-hexenol (98%), trans-3-hexenol (97%), vanillin (99%), 2,6-dimethoxyphenol (99%), linalool (97%), terpinen-4-ol (≥95%), α-terpineol (90%), nerol (≥97%), geraniol (98%), linalool oxide (≥97%), β-citronellol (95%), p-cymene (99%), terpinolene (≥85%), γ-terpinene (≥97%), limonene (97%), 1,8-cineole (99%), 1,4-cineole(≥98.5%), β-damascenone (≥98%), isoamyl alcohol (98%), benzyl alcohol (≥99%), 2-phenylethanol (≥99%), ethyl acetate (99%), ethyl butanoate (99%), ethyl 3-methyl butanoate ((≥98%), isoamyl acetate (≥95%), ethyl hexanoate (≥95%), phenylethyl acetate (99%), n-hexyl acetate (≥98%), ethyl lactate (≥98%), ethyl octanoate (≥98%), ethyl decanoate (≥98%), hexanoic acid (≥99%), octanoic acid (≥98%), α-phellandrene (95%), p-menthane-1,8-diol (97%), 3-methylbutanoic acid (99%), α-ionone (90%), 1-pentanol (99%), 1-butanol (≥99%), 2-butanol (≥99%), ethyl guaiacol (≥99%), vinyl guaiacol (≥98%), methyl-vanillate (99%) and ethyl vanillate (99%), were supplied by Sigma Aldrich (Milan, Italy). Dichloromethane (≥99.8%) and methanol (≥99.8%), were provided by Honeywell (Seelze, Germany). Sodium chloride (≥99.5%) was supplied by Sigma Aldrich (Milan, Italy).