Dominance of Frankia strains in stands of Alnus incana subsp rugosa and Myrica pensylvanica

To address issues of dominance and diversity of Frankia spp. strains, we se quenced 16S rRNA genes from root nodules and strains collected from Alnus i ncana subsp. rugosa (Du Roi) R.T. Clausen and Myrica pensylvanica Loisel. s tands. Of 22 strains isolated previously from A. incana, 16 had the same pa rtial rDNA sequence; the remaining 6 strains composed five additional group s. The groups identified by 168 rDNA analysis corresponded to phenotypic gr oups established previously by one- and two-dimensional polyacrylamide gel analysis, colony and hyphal morphology, and carbon source utilization patte rns. Dominance of one strain was also evident in nodules collected from a s ingle M. pensylvanica stand. The dominant strain had a partial 16S rDNA seq uence identical to that of Frankia alni strain CpI1.