Resumo

Soybean (Glicyne max L.) is a vegetable of large economic and nutritious importance. Brazil occupies the second place in the world grain productivity, which is protein-rich and source of vegetable oil. The high brazilian productivity is due to the crop breeding processes and to the inoculation with Bradyrhizobium japonicum and B. elkanii selected strains. These bacterial species establishes a symbiotic partnership with the soybean roots, resulting in the formation of structures named as nodules. The nitrogen necessary to the plant growth is supplied by the bacteria trough the Biological Nitrogen Fixation (BNF) process that occurs inside of nodules. These bacteria are used in the commercial inoculants to soybean as an alternative to the use of nitrogen fertilizers, resulting in savings and environmental advantages due to the non-utilization of chemicals fertilizers. Due to the necessity of a continuous search of Bradyrhizobium genotypes more efficient to the BNF process, it is necessary the identification of genes related to the BNF efficiency process with soybean to use as molecular markers in the strain selection programs. Therefore, this study aimed at identifying the presence of polymorphisms, trough the PCR-RFLP technique, in gene sequences of eighteen B. japonicum strains contrasting to this feature. The gene sequences studied were previously identified in the B. japonicum S 370 strain as related to the BNF efficiency in soybean. The chvE and blr4511 genes were amplified with the use of primers constructed based on the B. japonicum USDA 110 genome. The RestrictionMapper program was used for the selection of restriction enzymes to be use in the PCR-RFLP analysis. The PCR amplification product of chvE and blr4511 genes were digested with three different restriction enzymes and analyzed after 3% agarose gel electrophoresis. The results showed a high gene sequence conservation of the chvE and blr4511 genes between the strains analyzed, since the polymorphism was not possible to be identified by the PCR-RFLP technique. The chvE and blr4511 gene sequences of USDA 110 strains was compared to gene sequences from different rhizobia species and showed a high level of similarity (above 90%). The nucleotide sequence conservation of these genes may be related to the adaptive function that they may act during the evolutive process of rhizobia species.