Diversity of rhizobia isolated from nodules of indigenous tree legumes from the Brazilian dry forest

Abstract

The diversity of rhizobial isolates in tropical dry forests (TDF) has been studied due to the great importance of finding new species of bacteria capable of fixing nitrogen in tree legumes. In the Brazilian TDF (caatinga), Leguminosae is the most important family of plants, so the knowledge of microbial communities that make symbioses with native plants can help in the understanding of the interaction plant-microorganisms, as well as in the optimization of biological processes that can improve the cultivation system in an area so rich and understudied. In this study was determined the characteristics of rhizobia isolated from nodules of Mimosa tenuiflora (Willd.) Poir., Piptadenia stipulacea (Benth.) Ducke and Mimosa caesalpiniifolia Benth, grown in soils collected under caatinga vegetation. The phenotypic and molecular characterization of the isolates, with use of fingerprint markers such as BOX, REP, ERIC and BOX-PCR were performed. Amplification technique by duplex PCR with the nifH and nodC genes was used for the authentication of isolates. The results showed that given the variation found in the amplification of the nifH and nodC genes, the duplex PCR technique can show false-positive results, as these genes have a very large polymorphism. The lack of knowledge of isolates that make symbioses with these plants further help to conclude that this authentication technique cannot yet be applied to all legume-nodulating isolates. Regarding the analyses made with fingerprint markers, it was observed that all were very efficient in the ability to distinguish species and that the greater the number of markers used, the safer the knowledge on the taxonomy and diversity of rhizobia.