Frankia DNA extraction from root nodules and soils
The collected nodule and soil samples were transported to a laboratory in a cool box, and then we immediately extracted Frankia DNA. The root nodules were sterilized using 10% (v/v) Clorox bleach. One lobe was picked from each washed nodule, sliced using sterilized razor blades, and crushed using sterilized homogenization sticks. Bacterial DNA extraction from the crushed lobes and 300 mg of the soil samples from alder rhizosphere and riparian soils was performed using a DNeasy Blood & Tissue Kit (Qiagen) and NucleoSpin Soil (Macherey-Nagel), respectively.