01816naa a2200253 a 450000100080000000500110000800800410001910000190006024501320007926000090021152011170022065000130133765000150135065000160136565000160138165000160139765000090141365300120142265300130143465300210144765300120146870000190148077300630149914573732017-04-27       1992    bl ---       0--  u    #d1 aBALATTI, P. A.  aDifferential sensitivity of Rhizobium fredii strains to nodulation blocking on McCall soybeanbnodulation rates and efficiency.  c1992  aRhizobium freddi USDA257 infects but does not nodulate McCall soybean. Transposon mutant 257DH4 and wild-type strain USDA191 both produce Fix+ nodules on this cultivar. Nodulation of McCall by 257DH4 but not USDA191 is highly sensitive to the presence of USDA257 cells in the bacterial inoculum, a phenomenon termed nodulation blocking. We sought to explain this observation by separately comparing the infection and nodulation behavior of 257DH4 and USDA191. A given nunber of cells of USDA191 always generates more nodules than does the same number of cells of 257DH4, both on McCall and on supernodulating Williams soybean. USDA191 nodulates the primary root more rapidly, as indicated by nodule distribution profiles. Infections produced by USDA191 also are larger in number and develop faster than do either 257DH4 infections or the arrested infections produced by USDA257. These data all are consistent with the hypothesis that USDA191 escapes the effects of nodulation blocking because of its capacity to initiate and sustain the nodulation process more rapidly and at a lower inoculum cell concentration.  anitrogen  anodulation  aGlycine Max  aNitrogênio  aNodulação  aSoja  aFixacao  aFixation  aRhizobium fredii  aSoybean1 aPUEPPKE, S. G.  tPlant Physiology Biochemistrygv.30, n.2, p.193-199, 1992.