Use of the enzyme-linked immunosorbent assay (ELISA) in the detection of Rhizobium both in culture and from root nodules of soybeans and cowpeas'

The enzyme-linked immunosorbent assay (ELISA) was used to detect Rhizobium sp. in the "cowpea" group and R. japonicum both in culture and from nodules of glasshouse and field-grown plants. Double antibody sandwich (direct ELISA) and indirect ELISA were found to be equally sensitive in detecting rhizobia under controlled laboratory conditions. It was found that nodules preserved by freezing or drying over silica gel were equally good. No loss in sensitivity was detected when nodules were crushed directly in the microplates.