Variation in Colony Characteristics and Symbiotic Effectiveness of Rhizobium

Seventeen cultures of Rhizobium CB756 varied in symbiotic effectiveness and contained a number of different colony types. An examination of single colony isolates from one culture of CB756 indicated that colony characteristics of most isolates were unstable and did not breed true. There was a relationship between symbiotic effectiveness and colony type of the original isolate. The 3 most ineffective sub-strains were all isolated from large, gummy colonies whereas the most effective were isolated from pinpoint, dry colonies.