DNA extracted directly from the living nodules of Casuarina cunninghamiana, C.collina, C.glauca, Alnus cremastogyne, A.trabeculosa and Myrica rubra and also from 21 Frankia strains isolated from the root nodules of the actinorhizal plants in Fujian, including C. cunninghamiana, C.equisetifolia, C.glauca, A.cremastogyne and M.rubra. PCR amplification was conducted with the primers targeting the 3’ end of the 16S rDNA, the IGS, and the 5’ part of the 23S rDNA (i.e.,rrn region). PCR products were then analyzed by using a set of restriction endonucleases. Two distinct genetic groups were recognized on the basis of these restriction patterns. All Frankia strains associated with the host species of Casuarina were assigned to the same group. Frankia living in the nodules of Myrica and Alnus belonged to the other group. In Myrica-Alnus group, there was two sub-group which one included A.cremastogyme and the other contained A.trabeculosa and M.rubra. The results of RFLP analysis showed that the genetic diversity of Frankia associated with Casuarina could be lower, but Frankia existed in the soils of Fujian Province would have more richness in genetic diversity. The results also reflected that host plant has an ability to choose the strains to form a symbiont.
