Nodulation of Alnus japonica and Casuarina equisetifolia in liquid culture after inoculation with Frankia

摘要

Evaluation of infectivity and effectivity of different Frankia strains inoculated to Alnus japonica and Casuarina equisetifbila, in liquid culture system, was carried out. Plant materials of A. japonica and C. equisetifolia were grown in liquid culture (1/4-strength Hoagland's nutrient solution; pH 6.8; 100-ml glass bottles), and their roots were inoculated with strains of Frankia. Seedlings of A. japonica developed abundant root hairs and formed red swellings on lateral roots1week after inoculationwith a Frankia strain isolated from a root nodule of A. japonica. The red swellings developed into root nodules. Rooted cuttings of C equisetifolia formed root nodules 3 weeks after inoculation with Frankia strains isolated from root nodules of Casuarina. Nodule roots of C. equisetifolia grew upwards in the nutrient medium, exhibiting negative geotropism. These results demonstrated that liquid culture is a suitable method to evaluate nodule development over time by non-destructive observations. This method will be useful for further research on actinorhizal symbioses.