Isolation of frankia strains from root nodules of myrica rubra

Abstract Frankia strains were successfully isolated from Myrica rubra root nodules using a double-layer agar system consisting of an upper layer of 1% agar which included the endophytes and a lower layer of 1.5% agar which contained the nutrients. Colonies appeared within 1 month and their diameter increased from 0.5 to 1.0 mm 2 months after the inoculation. Hyphae, sporangia, and vesicles were observed in the colonies. The Frankia isolates grew well in liquid media supplemented with vitamins including biotin and p-aminobenzoic acid (modified Qmod medium; see Lalonde and Calvert 1979). The Frankia isolates grown in N-deficient modified Qmod medium exhibited an acetylene reducing activity. Nodules were formed on the roots of Myrica rubra by inoculation of the Frankia isolates and the acetylene reducing activity of the nodules amounted to 16 /anol C2H4·(g fr wt)-1·hr-1. No nodules were formed on Coriaria japonica after the inoculation of the isolates. These results suggest that the Frankia strains isolated ...