Symbioses between the root nodule‐forming, nitrogen‐fixing actinomycete Frankia and its angiospermous host plants are important in the nitrogen economies of numerous terrestrial ecosystems. Molecular characterization of Frankia strains using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) analyses of the 16S rRNA‐ITS gene and of the nif D– nif K spacer was conducted directly on root nodules collec...