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A Rhizobium leguminosarum Biovar trifolii Locus Not Localized on the Sym Plasmid Hinders Effective Nodulation on Plants of the Pea Cross-Inoculation Group

September 1997 , Volume 10 , Number  7
Pages  938 - 941

Henk P. Roest , Ine H. M. Mulders , Herman P. Spaink , Carel A. Wijffelman , and Ben J. J. Lugtenberg

Leiden University, Institute of Molecular Plant Sciences, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, Netherlands

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Accepted 4 June 1997.

Introduction of the Sym plasmid pRL1JI into the cured Rhizobium leguminosarum bv. trifolii strain RCR5 resulted in a strain, designated RBL5523, that was expected to nodulate plants of the pea cross-inoculation group. However, effective nodulation occurred only on Vicia sativa plants, not on V. hirsuta or Pisum sativum. After random Tn5 mutagenesis, a derivative of RBL5523 was isolated that effectively nodulated and fixed nitrogen on P. sativum and V. hirsuta. Characterization of the mutant, RBL5787, indicated the cell surface components, extracellular polysaccharides, lipopolysaccharides, and outer membrane proteins, as well as the pattern of Nod metabolites, were indistinguishable from those of the parental strain. To obtain an indication of the function of the mutated locus, the flanking regions were sequenced and used to perform searches in protein and nonredundant nucleotide databases. No significant similarity or homology with any known sequence was detected.

Additional keywords: host specificity, N2 fixation, R. leguminosarum bv. viciae, transposon.

© 1997 The American Phytopathological Society