Investigations upon the Antigenic Relationships among the Root-Nodule Bacteria of the Soybean, Cowpea, and Lupine Cross-Inoculation Groups

Abstract

Antisera were prepared with untreated, heated, and washed-heated cells of 4 strains of Rhizobium japonicum, 3 of R. lupini and 3 of the Rhizobium for cowpeas, and were used in simple agglutination tests against similar antigens prepared from 54 strains of root-nodule bacteria from plants in the soybean, cowpea and lupine cross-inoculation groups. A great number of serological types were found to exist among the strains tested; antigenic constituents of the strains within each group were similar. One serological type may be made up of rhizobia from one species of plant, or from two or even three species. No correlation was found between ability to cross-agglutinate and to cross-inoculate. Antisera for the different antigenic modifications of soybean, cowpea and lupine bacteria failed to agglutinate alfalfa, clover or pea bacteria.