Preparation of DNA mixtures
Two Rlt strains (SM3 and SM170C) were chosen based on theirrecA , rpoB , nodA, and nodD sequence divergence, with a minimum of 3 base pair differences in the amplicon region required for each gene. Strains were grown on Tryptone Yeast agar (28°C, 48hrs). Culture was resuspended in 750ul of the DNeasy Powerlyzer PowerSoil DNA isolation kit (QIAGEN, USA) and DNA was extracted following the manufacturer’s instructions. DNA sample concentrations were calculated using QuBit (Thermofisher Scientific Inc., USA). DNA samples of the two strains were diluted to the same concentration and mixed in various ratios (Supplementary Table S1) .