2.2.2 Rhizosphere secretions
We used ethyl acetate to extract the rhizosphere soil secretions and then profiled them using gas chromatography-mass spectrometry (GC-MS) (TSQ 8000TM Evo Triple quadrupole GC-MS, Thermo Fisher Scientific Co., Ltd., Shanghai, China) (Carvalhais et al., 2015; Liu et al., 2015).