The Occurrence of the Root-nodule Endophytes of Alnus glutinosa and Myrica gale in Soils

SUMMARY: Twenty-one soil samples from sites in West Scotland where alder (Alnus glutinosa) has not grown for many years were examined for the presence of the alder root-nodule endophyte by observing the production of nodules on test plants which were grown (a) in water culture and their roots inoculated with an aqueous suspension of a soil sample, or (b) in the soil itself. Twelve of the samples gave positive results, most of the remaining samples were at pH < 4. Ten samples from sites free from bog myrtle (Myrica gale) were similarly tested for the corresponding endophyte; 8 of these gave positive results. To explain these results it seems necessary to assume either that infective bodies of the endophyte can survive in soils for long periods, though not grow; or that the endophytes can grow saprophytically in soils and thus are not near-obligate symbionts.