A colony immunoblot assay using monoclonal antibodies was developed to permit rapid Rhizobium strain identification and quantification in alfalfa inoculants and preinoculated seed produced for the Canadian market. Plate-count colonies were pressed onto nitrocellulose membranes and then allowed to react with specific monoclonal antibodies. The monoclonal antibody reaction was then amplified by reaction with goat anti-mouse antibody and the goat antibody reaction further amplified and detected with rabbit anti-goat antibody conjugated to alkaline phosphatase. A precipitating substrate for alkaline phosphatase was used to form purple spots on the membrane surface corresponding to positive reactions between the monoclonal antibody and the colony imprint. Results of analysis of 13 peat-base inoculants and 20 preinoculated seed samples by traditional most probable number and by immunoblot analysis indicated that the colony immunoblot test could be used as a reliable initial screen for viable Rhizobium cell numbers. Key words: Rhizobium, monoclonal antibody, immunoblot, Rhizobium inoculant analysis.
Developmental regulation of a Rhizobium cell surface antigen during growth of pea root nodules.