PCR-RESTRICTION FRAGMENT LENGTH POLYMORPHISM IDENTIFICATION AND HOST-RANGE OF SINGLE-SPORE ISOLATES OF THE FLEXIBLE FRANKIA SP STRAIN UFI-132715

Twelve single-spore isolates of the flexible Elaeagnus-Frankia strain UFI 132715 fulfilled the third and the fourth of Koch's postulates on both Alnus and Elaeagnus axenic plants. Seminested nifD-nifK PCR-restr iction fragment length polymorphisms provided evidence for the genetic uniformity of the single-spore frankiae with the mother strain and it s plant reisolates and allowed their molecular identification directly inside Alnus and Elaeagnus nodules. The clonal nature of these single -spore-purified frankiae should allow safe mutagenesis programs, while their flexible phenotype makes them a powerful tool for understanding the molecular interactions between Frankia strains and actinorhizal p lants and for identifying Frankia nodulation genes.