Phenotypic and molecular characteristics of rhizobia isolated from nodules of peanut (Arachis hypogaea L.) grown in Brazilian Spodosols

Abstract

Peanut (Arachis hypogaea L.) is an important crop that can fix nitrogen through symbiosis with rhizobia. Rhizobia populations with diverse characteristics than those traditionally described as peanut microsymbionts have been found in tropical soils. With the objective of studying the diversity and phylogeny of these rhizobia, 22 bacterial strains were isolated from nodules of seven peanut varieties grown in Spodosols of Pernambuco State, Brazil. The isolates were examined in culture medium by means of some of their phenotypic characteristics and tested for intrinsic antibiotic resistance (IAR). DNA profiles were determined with the BOX-PCR and compared with 19 reference strains. All isolates showed rapid growth, and most of them acidified the culture medium. In general, high antibiotic resistance was observed to penicillin G, chloramphenicol and tetracycline and susceptibility was observed to neomycin, erythromycin and rifampicin. The analysis of their phenotypic characteristics, that is, colony morphology and IAR, provided little information about the phylogeny of the isolates. However, using compilation of phenotypic and molecular characteristics, we were able to observe a great diversity of these rhizobia and to reveal the presence of new species.

Keywords: Antibiotic resistance, Arachis hypogaea L., BOX-PCR, colony morphology, diversity

African Journal of Biotechnology Vol. 12(17), pp. 2147-2156