Isolation and characterization of endophytic bacteria from soybean (Glycine max L.)

Abstract

Endophytic bacteria colonize the internal tissue of the plant usually forming beneficial association with their host. The main aim of this study was to genotypically and phenotypically characterize endophytic bacteria isolated from roots, stems and nodules of two soybean cultivars (AFZG Ana and Gabriela). A total of 29 endophytes were isolated from three different tissues of soybean. Genotypic characterization included rrs genes sequencing. Among soybean endophytes five different genera of bacteria were identified: Pseudomonas spp., Sphingomonas spp., Bradyrhizobium spp., Rhizobium spp., and Agrobacterium spp. Most of the isolates were Gram negative, rod-shaped, without capability of capsule production. The variability of the phenotypic characteristics of isolates was demonstrated, as well as the resistance to adverse environmental conditions such as high temperature, increased salt content, and low and high pH values. Most strains showed tolerance to the specific antibiotics. Most of the catalase positive isolates belong to Bradyrhizobium or Rhizobium spp., while the catalase negative isolates belong to the Pseudomonas, Sphingomonas and Agrobacterium spp. It was also shown that 85% of the tested isolates were oxidase negative while those that were positive belong to the Pseudomonas spp. Further characterization of endophytes is needed to determine their influence on plant growth.

Keywords

• endophytic bacteria
• soybean (glycine max l.)
• 16s rrna gene sequencing
• phenotypic characterization