Soluble Sugar Extraction and GC-MS Analysis

Soluble sugars were extracted from the roots of Chinese cabbage at weeks 2, 3, 4, and 5 after P. brassicae inoculation according to the previous method [45 (link)]. The GC-MS QP2010 ultra instrument (Shimadzu, Kyoto, Japan) was used for the gas quality analyses. The detailed setting information is as follows: the inlet temperature was 300 °C, the split ratio was 10:1, the carrier gas was high-purity helium, and the flow rate was 1 mL/min. The heating program was as follows: 120 °C for 3 min, 5 °C/min to 210 °C for 5 min, and 15 °C/min to 300 °C for 10 min. The ion source temperature was 200 °C, and the interface temperature was 280 °C. The solvent removal time was 3 min, and the scanning m/z was 45–500. Soluble sugars were extracted from three biological replicates at each time point. Gas quality analyses were repeated three times for each treatment.