Isolation and Characterization of a pSym Locus of Rhizobium sp. BR816That Extends Nodulation Ability of Narrow Host Range Phaseolus vulgaris Symbionts to Leucaena leucocephala. Pieternel van Rhijn. F. A. Janssens Laboratory of Genetics, KU Leuven, W. de Croylaan 42, B-3001 Heverlee, Belgium. Ellen Luyten, Katrien Vlassak, and Jos Vanderleyden. F. A. Janssens Laboratory of Genetics, KU Leuven, W. de Croylaan 42, B-3001 Heverlee, Belgium. MPMI 9:74-77. Accepted 21 September 1995, Copyright 1996 The American Phytopathological Society.

Introduction of a cosmid library of megaplasmid DNA of Rhizobium sp. BR816, a broad host range Rhizobium strain, into R. etli CE3, a narrow host range bean symbiont, resulted in the isolation of a transconjugant that could effectively nodulate Leucaena leucocephala. Analysis of the corresponding cosmid, pBRF2, revealed the presence of genes required for eliciting nitrogen-fixing nodules on L. leucocephala. Subcloning and Tn5 tagging identified a locus responsible for the host range extension. Sequence analysis of this locus revealed an ORF that shows significant identity with NodO of R. leguminosarum bv. viciae.