Molecular identification of Bradyrhizobium japonicum strains isolated from root nodules of soybean (Glycine max L.)

Abstract

The aim of this study was to isolate and identify Bradyrhizobium japonicum strains on the basis of molecular characteristics. From root nodules of different soybean cultivars were obtained 56 isolates, characterized according to morphological, cultural, and biochemical properties. Among these isolates, 33 isolates showing resemblance with Bradyrhizobium sp. were further subjected to molecular identification. Following DNA extraction, a partial 16S rDNA gene sequence from the isolates was amplified by PCR using universal primers fD1 (27F) and rP3 (1492R). Purification and sequencing of the amplified fragments were done in the bio?technology company Macrogen, Seoul, South Korea. Sequences were analyzed using the pro?gram FinchTV and BLAST (Basic Local Alignment Search Tool) and compared to sequences in GenBank and the Bradyrhizobium ID-database for identification. Comparison of the se?quences with the Bradyrhizobium ID-database showed that all tested isolates were identified as Bradyrhizobium japonicum. Each isolate was deposited in the NCBI GenBank database under a unique accession number. Identification of Bradyrhizobium species from root nodules of soybean is of great importance because the symbiosis between rhizobia and legumes are a cheaper and usually more effective agronomic practice for ensuring an adequate supply of nitrogen for legumes, while preserving and improving fertility and productivity of soils.