Abstract
Using a theoretical method, the highest possible per cent deoxyribonucleic acid homology between 26 isolates of Rhizobium japonicum was determined. The homologies between the isolates and a reference strain ranged from 69.5% to 95%. Least significant difference analysis resulted in three statistically different but overlapping clusters. It was concluded on the basis of homology data that the species is a valid one, although one which shows considerable diversity.