DIVERSITY OF FRANKIA NODULE ENDOPHYTES OF THE ACTINORHIZAL SHRUB CEANOTHUS AS ASSESSED BY RFLP PATTERNS FROM SINGLE NODULE LOBES

Root nodules of the actinorhizal shrub Ceanothus were collected from s even sites from its native range. DNA was extracted from individual no dule lobes using a cetyl trimethyl ammonium bromide (CTAB) extraction procedure. Three DNA probes were used in combination with two restrict ion endonucleases to evaluate the extent of restriction fragment lengt h polymorphism (RFLP) diversity within and among populations of Ceanot hus endophytes. We observed some diversity using a nif DH gene probe; however there was no correlation of RFLP pattern and geographic site. Using two random Frankia probes, we observed more diversity among the Ceanothus endophytes than with the nif probe. Differences in RFLP patt erns were observed among plants at a single geographic site and betwee n geographical sites. The results demonstrated that considerable diver sity exists among Frankia strains symbiotic with Ceanothus, as has bee n shown for pure-cultured Frankia strains isolated from other actinorh izal genera. We have also demonstrated the usefulness of this method f or the study of Frankia ecology in planta.