Evaluation of the diversity of rhizobia in Brazilian agricultural soils cultivated with soybeans

The diversity of rhizobia in agricultural soils planted with soybean (Glycine max L.) and managed under conventional or no-tillage practices was evaluated by using a combination of trap-host capture and DNA fingerprinting approaches. Fifty-eight rhizobia isolates were captured using pigeonpea (Cajanus cajan L.) as a trap-host and characterised by using the RAPD DNA fingerprinting technique, yielding 25 different RAPD profiles. The application of the Shannon-Weaver diversity index demonstrated that the diversity of rhizobia was significantly reduced in soil samples from plots cultivated with soybean compared with original uncultivated pasture plots. (C) 1999 Elsevier Science B.V. All rights reserved.