Genetic diversity of rhizobia from natural populations varies with the soil dilution sampled

Rhizobia were isolated from root nodules of three tree legumes inoculated with dilution series of two tropical soils. The diversity of the isolates obtained from different soil dilutions was assessed by PCR-RFLP analysis of the internally transcribed spacer (ITS) region between the 16S and 23S rRNA genes. In both soils there was a strong effect of dilution on the genetic diversity of the populations with apparent diversity decreasing with increasing dilution.