16S rRNA 40:60 v/v (field soil:Fafard), inoculated with genotype
DNA extractions were sent to the Genomics Core Lab at the University of Tennessee, Knoxville, for amplicon library preparation and sequencing. The V3V4 region of the 16S rRNA gene was amplified using primers 515Fb (Parada et al., 2016) and 806Rb (Apprill et al., 2015) with Nextera-compatible adapters in a two-step PCR protocol. The first PCR (25 cycles) used KAPA HiFi HotStart ReadyMix with ~20 ng template DNA. Products were verified by agarose gel electrophoresis, purified with AMPure beads, and indexed in a second PCR (8 cycles). Indexed amplicons were purified, quantified, pooled at equimolar concentrations, quality-checked on a Bioanalyzer, and sequenced on an Illumina NextSeq 1000 using 2  300 bp paired-end chemistry.