Analysis of Rice Plant Volatiles

Plant VOCs were collected with a closed loop dynamic headspace sampling system, similar to the method described by Sun et al.59 (link). One milliliter of n-Hexane (Tedia, USA) was applied to elute VOCs from absorbent traps and 1300 ng Nonyl acetate (Sigma, Switzerland) was added to each sample as an internal standard. VOCs emitted from the Xoo infected rice and control rice plants were collected for 24 h (16 h in light and 8 h in darkness) at room temperature; BPH-induced plant volatiles from rice plants (each rice plant was also infested with 15 gravid female adults for 24 h) were collected for 8 h in the light (20000 lx) as described by Lou et al.60 (link). Each treatment contained three to five biological replicates.
Gas chromatography–mass spectrometry (GC/MS) analyses of VOCs were performed on a QP-2010 GC/MS instrument (Shimadzu, Japan) equipped with an HP-5 MS fused-silica column (30 m × 0.25 mm × 0.25 μm). (Agilent Technologies, http://www.agilent.com). Helium (1 ml/min) was used as the carrier gas, and the initial oven temperature was 40 °C, held for 1 min, ramped at 8 °C min⁻¹ to 300 °C held for 5 min. VOCs were identified by comparing their GC retention indices and MS spectra with those from the NIST11 library. The Retention index for each compound was determined using a series of straight chain alkanes (C7-C30) as standards.