Rhizobia native from Rio Grande do Sul simbiotically efficient in Lotus glaber/Rizobios nativos do Rio Grande do Sul simbioticamente eficientes em Lotus glaber

Forage legumes besides contributing to increase the supply of high protein content forage are also good cover for the soil surface. Among the legumes with high potential forage, the genus Lotus has been outstanding. This research aimed to selectnative rhizobia efficient in fixing nitrogen with Lotus glaber, from soil samples of five localities of Rio Grande do Sul. A total of 259 rhizobia isolates were obtained, which were evaluated based on colony morphology and in vitro melanin production. Among them, 1 5 isolates were selected for the evaluation of the symbiotic nitrogen fixation efficiency in greenhouse experiments and genetically characterized by genomic DNA fingerprinting, PCR amplification with BOX and ERIC primers. Only five isolates produced melanin. Nine isolates were more efficient than strain SEMIA 830, which is authorized for the production of commercial inoculants of L. glaber in Brazil. In relation to the genetic characterization, the isolates have shown no similarity with the commercial strains, indicating that in the soils of Rio Grande do Sul there are autochthonous rhizobia capable of efficient symbiotic nitrogen fixation with L. glaber, which might be recommended for field evaluations, aiming a future production of inoculants for this legume in Brazil. Key words: forrage legumes, inoculante, Lotus glaber, symbiotic nitrogen fixation. As leguminosas forrageiras, alem de contribuirem para o aumento da oferta de forragem com alto teor de proteina, tambem sao importantes como cobertura vegetal de solos. Entre as leguminosas com grande potencial forrageiro, especies do genero Lotus tem se destacado. Este trabalho visou a selecao de rizobios nativos eficientes em Lotus glaber a partir de amostras de solo de cinco localidades do Rio Grande do Sul. Obtiveram-se 259 isolados de rizobios, que foram avaliados quanto a morfologia colonial e producao de melanina. Destes, 15 isolados foram selecionados para avaliacao da eficiencia na fixacao simbiotica de nitrogenio em experimento em casa de vegetacao e caracterizados geneticamente por comparacao do perfil eletroforetico dos produtos de amplificacao do DNA genomico, por PCR com os oligonucleotideos iniciadores BOX e ERIC. Apenas cinco isolados produziram melanina. Nove isolados foram mais eficientes do que a estirpe SEMIA 830, que e autorizada para a producao de inoculante para L. glaber no pais. Na caracterizacao genetica, observou-se que nenhum isolado apresentou identidade com as estirpes recomend