Key words Nodulation
Rhizobium sp. (Cicer)
Springer Online Journal Archives 1860-2000
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Abstract We constructed lacZ fusions in Rhizobium sp. (Cicer) by random Tn5-lacZ mutagenesis. The lacZ+ fusants formed blue colonies on a Rhizobial minimal medium containing 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal). Rhizobium sp. (Cicer) fusant HSL-2 was identified in nodules and soil in a mixed population on the basis of the lacZ+ phenotype. Nodule occupancy of inoculated Rhizobium sp. (Cicer) HSL-2 (lacZ+) was assessed by directly streaking the nodule sap on X-gal plates. This method revealed differences between rhizobia carrying identical antibiotic markers. The rhizobial population in soil was estimated by direct plate counts using a medium containing X-gal. Introduction of lacZ into the Rhizobium sp. thus provided a simple and direct method for identifying strains from nodules and soil.
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