02254naa a2200217 a 450000100080000000500110000800800410001902400350006010000180009524501070011326000090022052016130022965000220184265000130186465000290187765000090190670000160191570000210193170000200195277300640197219105982018-04-17       2011    bl uuuu     u00u1 u    #d7 a10.1007/s11274-011-0964-32DOI1 aTORRES, A. R.  aGenetic variability in Bradyrhizobium japonicum strains nodulating soybean [Glycine max (L.) Merrill].  c2011  aBrazil has succeeded in sustaining production of soybean [Glycine max (L.) Merrill] by relying mainly on symbiotic N2 fixation, thanks to the selection and use in inoculants of very effective strains of Bradyrhizobium japonicum and Bradyrhizobium elkanii. It is desirable that rhizobial strains used in inoculants have stable genetic and physiological traits, but experience confirms that rhizobial strains nodulating soybean often lose competitiveness in the field. In this study, soybean cultivar BR 16 was singleinoculated with four B. japonicum strains (CIAT 88, CIAT 89, CIAT 104 and CIAT 105) under aseptic conditions. Forty colonies were isolated from nodules produced by each strain. The progenitor strains, the isolates and four other commercially recommended strains were applied separately to the same cultivar under controlled greenhouse conditions. We observed significant variability in nodulation, shoot dry weight, shoot total N, nodule efficiency (total N mass over nodule mass) and BOX-PCR fingerprinting profiles between variant and progenitor strains. Some variant strains resulted in significantly larger responses in terms of shoot total N, dry weight and nodule efficiency, when compared to their progenitor strain. These results highlight the need for intermittent evaluation of stock bacterial cultures to guarantee effective symbiosis after inoculation. Most importantly, it indicates that it is possible to improve symbiotic effectiveness by screening rhizobial strains for higher N2 fixation capacity within the natural variability that can be found within each progenitor strain.  aNitrogen fixation  aSoybeans  aFixação de nitrogênio  aSoja1 aKASCHUK, G.1 aSARIDAKIS, G. P.1 aCUNHA, M. H. da  tWorld Journal of Microbiology and Biotechnology, Dec. 2011.