Rhizobia were isolated from root nodules of three tree legumes inoculated w
ith dilution series of two tropical soils. The diversity of the isolates ob
tained from different soil dilutions was assessed by PCR-RFLP analysis of t
he internally transcribed spacer (ITS) region between the 165 and 23S rRNA
genes. In both soils there was a strong effect of dilution on the genetic d
iversity of the populations with apparent diversity decreasing with increas
ing dilution. (C) 2001 Elsevier Science Ltd. All rights reserved.