SELECTION OF SALT TOLERANT CASUARINA-GLAUCA AND FRANKIA

Increasing NaCl concentrations up to 250 mM significantly affected Frankia growth and also growth and N2 fixation of Casuarina glauca. There was no correlation between the response to salinity of Frankia strains grown in vitro and their effectivity when associated with plants under salt-stressed conditions. Under saline conditions a Frankia strain, namely Thr, isolated from an Egyptian soil and poorly salt tolerant in vitro, appeared to improve N2 fixation better than other strains when associated with Casuarina glauca provenance E known for its salt tolerance in the field. It is suggested that, once compatible Frankia strains are identified, selection of salt tolerant plant hosts is a critical requirement to obtain effective Casuarina-Frankia symbioses tolerant to salinity.