Data/hora: 24/06/2024 21:59:44

Biblioteca(s): | Embrapa Soja.
Data corrente: | 22/12/2005
Data da última atualização: | 22/12/2005
Autoria: | HUNGRIA, M.; MENNA, P.; GERMANO, M. G.; CHUEIRE, L. M. O.; BANGEL, E. V.; CAMPO, R. J.
Título: | Diversity of a Brazilian collection of rhizobial strains.
Ano de publicação: | 2005
Fonte/Imprenta: | In: WANG, Y. P.; LIN, M.; TIAN, Z. X.; ELMERICH, C.; NEWTON. W. E. (Ed). Biological nitrogen fixation, sustainable agriculture and the environment. Dordrecht: Springer, 2005. p. 413.
Idioma: | Inglês
Notas: | Proceedingsof the 14th International Nitrogen Fixation Congress.
Conteúdo: | The Leguminosae is  one of the largest plant families with over 18,000 species classified into around 650 genera: most are capable of effective symbioses with rhizobial strains. Howerver, despite reports of high strain diversity, especially in the tropics, there are less than 40 described rhizobial species. Ribosomal sequences, emphasinzing 16S rRNA gene ( 1.5 kb), are the method of choice for tracing bacteria phylogenies. Speciation of genera can be enhanced by analaysis of other ribosomal genes because both the 23S rRNA ( 2.3 kb) and the 16S-23S rRNA intergenic space (ITS) show higher variability than 16S rRNA. Analyses of rhizobial ribosomal genes have used RFLP-PCR, as well as partial or complete sequencing of bases. In Brazil, there are 200 rhizobial strains recommended for 95 legume species, but little is known of their genetic diversity. A Brazilian culture collection of 119 strains of Bradyrhizobium, isolated from thirty-three legume species, representing nine tribes and all three subfamilies, were analyzed by RFLP-PCR of the 16S rRNA, 23S rRNA and ITS region, each with three restriction enzymes. 43  of those atrains are recommended in Brazil as the most effective for 31 host legumes. For the 16S rRNA gene, reference strains of B. japonicum fit into two major clusters at 50% similarity, whereas two other cluster (at 53% similarity) were composed of strains of B. elkanii; all strains were joined at a final level of similarity of 28%. The higher variability in the ITS and 23rRNA resulted in final grouping at very low level of similarities, 27% and 16% respectively. Considering the three ribosomal regions, two great groups were visualized, related to B. japonicum (with most strains from soybean) and B. elkanii (most strains from indigenous legumes), at similarity levels of 54 and 46%, respectively, and at least two new clusters that might represent new species. The complete 16S rRNA sequence for another set of 80 rhizobial strains from 30 different legume species (23 recommended as most effective) were clustered within the genera Rhizobium, Sinorhizobium, Mesorhizobium and Bradyrhizobium. Three strains, recommended for Clitoria fairchildian, Piptadenia gonoacantha and Ormosia nitida, were clustered with Burkholderia sp. strain TJ182. This collection of strains indicates an extremely high level of genetic diversity in the tropics.
Categoria do assunto: | --
Registro original: | Embrapa Soja (CNPSO)
Exemplares: | CNPSO - (25862-1) - UPC - SP - -- - 10720 -  - 10720 - DIS