AMPLIFICATION OF 16S RIBOSOMAL-RNA GENES FROM FRANKIA STRAINS IN ROOT-NODULES OF CEANOTHUS-GRISEUS, CORIARIA-ARBOREA, CORIARIA-PLUMOSA, DISCARIA-TOUMATOU, AND PURSHIA-TRIDENTATA

To study the global diversity of plant-symbiotic nitrogen-fixing Frank ia strains, a rapid method was used to isolate DNA from these actinomy cetes in root nodules, The procedure used involved dissecting the symb iont from nodule lobes; ascorbic acid was used to maintain plant pheno lic compounds in the reduced state, Genes for the small-subunit rRNA ( 16S ribosomal DNA) were amplified by the PCR, and the amplicons were c ycle sequenced, Less than 1 mg (fresh weight) of nodule tissue and few er than 10 vesicle clusters could serve as the starting material for t emplate preparation, Partial sequences were obtained from symbionts re siding in nodules from Ceanothus griseus, Coriaria arborea, Coriaria p lumosa, Discaria toumatou, and Purshia tridentata. The sequences obtai ned from Ceonothus griseus and P. tridentata nodules were identical to the sequence preciously reported for the endophyte of Dryas drummondi i. The sequences from Frankia strains in Coriaria arborea and Coriaria plumosa nodules were identical to one another and indicate a separate lineage for these strains. The Frankia strains in Discaria toumatou n odules yielded a unique sequence that places them in a lineage close t o bacteria that infect members of the Elaeagnaceae.