In the pot experiment, three plant samples from each treatment were randomly collected. Soil from the rhizosphere was collected according to the method described by Hervás et al. (1998). The cucumber plants were carefully removed from the pots and gently shaken to remove soil. The soil that remained on the root system was defined as rhizosphere soil. Soil DNA was extracted with the E.Z.N.A.™ Soil DNA kit (Omega Bio-tek, Inc., Norcross, GA, USA) according to the manufacturer's instructions