Genetic characterization and nitrogen fixation capacity of Rhizobium strains on common bean

Abstract

This study aimed to genetically characterize four new Rhizobium strains, and to evaluate their nodulation and fi xation capacity compared to commercial strains and to native rhizobia population of a
Brazilian Rhodic Hapludox. Two experiments were carried out in randomized blocks design, under greenhouse conditions, in 2007. In the fi rst experiment, the nodulation and nitrogen fi xation capacity of new strains were evaluated, in comparison to the commercial strains CIAT-899 and PRF-81 and to native soil population. It was carried out in plastic tubes fi lled with vermiculite. DNA extractions and PCR sequencing of the intergenic space were made from the isolated pure colonies, in order to genetically characterize the strains and the native
rhizobia population. In the second experiment, the nodulation and productivity of common beans Perola cultivar were determined, with the use of evaluated strains, alone or in mixture with PRF-81 strain. It was carried out in pots fi lled with soil. The native soil population was identifi ed as Rhizobium sp. and was ineffi cient in nitrogen fi xation. Three different Rhizobium species were found among the four new strains. The LBMP-4BR and LBMP-12BR new strains are among the ones with greatest nodulation and fi xation capacity and exhibit differential responses when mixed to PRF-81.