design: DNA was extracted from homogenized (Tissuelyzer II) root tips using Dneasy plant kit Pro (Qiagen). After PCR amplification of the ITS2 region (Fwd: CTAGACTCGTCAHCGATGAAGAACGYRG; Rev: TCCTSCGCTTATTGATATGC), another round round of PCR was used to attach index sequences to the primer ends of the DNA fragments. After each PCR, the DNA was purified by use of magnatic beads. Lastly, samples were pooled equimolarly and sequenced on Illumina MiSeq (PE300). Plant reads were used to assign the identify of the collected root (i.e., the host identity).