Isolation of Frankia from the root nodules of Elaeagnus macrophylla and Alnus sieboldiana and their infectivities to the host plants

Abstract

We isolated endophytic Frankia from the root nodules of Elaeagnus macrophylla and Alnus sieboldiana and examined the infectivity of the isolates to the host plants.
One strain from E. macrophylla and 13 strains from A. sieboldiana were isolated by the simple method of suspending the nodule homogenate directly in liquid Qmod medium. Hyphae, sporangia and vesicles, which are morphological characteristics of Frankia, were observed in the E. macrophylla isolate. However, only hyphae and sporangia were observed in the A. sieboldiana isolate.
The E. macrophylla isolate formed nodules on the roots of the host plant and the average acetylene reduction activity (ARA) was 17.7±6.9μmol C₂H₄h^-1 (g fresh wt nod.)^-1. Eleven strains isolated from A. sieboldiana formed nodules on the root of the host plants, but 2 strains did not nodulate. The average ARA was 4.22±3.73μmol C₂H₄h^-1 (g fresh wt nod.)^-1.