BANGEL, E. V.

BARCELLOS, F. G.

BATISTA, J. S. S.

BINDE, D. R.

CAMPO, R.

CHUEIRE, L. M. de O.

HUNGRIA, M.

MARCELINO, F. C.

MENDES, I. de C.

MENNA, P.

OLIVEIRA, L. R.

REIS JUNIOR, F. B. dos

RIBEIRO, R. A.

RODRIGUES, E. P.

Portuguese

Repository Open Access to Scientific Information from Embrapa

1Sl Intemational INCT Symposium on BNF - CONFERENCE ABSTRACTSC9. Diversity and Ecology of Rhizobial Strains Used in CommercialInoculants in BrazilHungria1.2, M., Menna1.2, P., Chueire1•2, L. M. O., Mendes2,3, I. C., Banqel", E. V,Barcetlos', F. G., Bansta'", J. S. S., Ribeiro1,6, R A., Btnde', D. R, dos ReisJunior", F. B., Ouveíra'", L. R, Rodrigues1,2, E. P, Marcelin01, F. C., Campo', RJ.'Ernbrapa Soja, Cx. Postal 231, 86001-970, Londrina - PR, Brazil2CNPq-MCT3Embrapa Cerrados, Cx. Postal 8223, 73301-970, Planaltina - DF, Brazil4FEPAGRO, Rua Gonçalves Dias 579, 90130-060, Porto Alegre - RS, Brazil5CAPES6Fundação Araucária(hungria@cnpso.embrapa.br)With more than 30 million doses of rhizobial inoculants marketed peryear, it is probable that Brazilian agriculture benefits more than that of any othercountry from symbiotic N2 fixation. Selection programs are mandatory toguarantee the maximization of the contribution of the biological process andhave identified strains that are recommended for use in commercial inoculantsfor almost one-hundred leguminous crops. We have analyzed ribosomal andhost keeping genes and rep-PCR profiles of 122 of those strains. Polyphasicapproaches have detected a very high levei of genetic diversity among thosestrains, but apparently with no relation between phylogeny of rhizobia and of thelegume host. Multilocus sequence analysis (MLSA) of housekeeping genes(atpO, dnaK, glnll, gltA, recA and rpoA) has proven to be a reliable way ofproviding information on phylogenetic relationships and taxonomy, being alsovery useful in the identication of rhizobial strains potentially representative ofnew species.More than one-hundred experiments performed by our group haveproven that a massive inoculation with selected strains of Bradyrhizobiumjaponicum and B. elkanii can significantly increase grain yields even in soilswithhigh populations of established soybean bradyrhizobia. Howeve r, in a series ofstudies in which we have re-íscíateo soybean rhizobia from areas previouslyinoculated with exotic B. jeoonicum and B. elkanii strains, we found a high leveiof genetic diversity in comparison to the putative parental strains. In one ofthose experiments genetic variability was such that even within a geneticallymore stable group, such as that of CPAC 15, only 6.4% of the isolates showedhigh similarity to the inoculant strain, whereas none was similar to CPAC 7.High rates of horizontal transfer of the symbiotic island from inoculant strains toindigenous rhizobia have also been observed, and included transference ofgenes to bacteria belonging to other genera. The results highlight the strategiesthat bacteria may commonly use to obtain ecological advantages, as theacquisition of genes to establish effective symbioses with an exotic hostlegume.New insights in the ecology of soybean and common bean (Phaseolus20I"Intemational INCT Symposium on BNF - CONFERENCE ABSTRACTSvulgaris L.) inoculant strains have also been achieved by means of genomicand proteomic approaches, with an emphasis on comparative studies of naturalvariant strains differing in competitiveness or in the capacity of fixing N2.Genomic drafts were obtained and others are in progress with common beanand soybean inoculant strains, and highlight several putative genes that mightbe related to the high competitive and saprophytic capacity of these strains.Functionality of some of those genes has been confirmed by proteomics andRT-qPCR, and highlight the role of some interesting genes, e.g. nopP in B.japonicum strain CPAC 15 and nodG in R. tropici strain PRF 81. Mostinteresting are several genes that play key roles and might explain the broadcapacity of adaptation of these strains to a variety of soils and environmentalconditions .•.21

Diversity and ecology of rhizobial strains used in commercial inoculants in Brazil.

http://www.alice.cnptia.embrapa.br/bitstream/doc/574317/1/digitalizar0362.pdf

Diversity and ecology of rhizobial strains used in commercial inoculants in Brazil.

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