Symbiotic ability of diverse Frankia strains on Casuarina glauca plants in hydroponic conditions

Frankia is a soil actinomycete that forms nitrogen-fixing root nodule symbioses with eight angiosperms families including Casuarinaceae. Knowledge on symbiotic performance of several isolated strains with Casuarina species is limited. In this study, we characterized a collection of Frankia strains based on their growth kinetics and their symbiotic ability with Casuarina glauca specie. Results showed that Frankia strains Allo2, CcI3, CeD and Cg70.9 do not exhibit the same symbiotic ability both for their infectivity and effectiveness towards Casuarina glauca. All strains were able to infect and improve C. glauca plants growth. Frankia isolate CcI3 better improved plants height while CeD and Cg70.9 strains formed more nodules on inoculated plants roots. However, there is no correlation between the number of nodules formed and the effectiveness of strains. These preliminary results give ideas on which Frankia strains to use for obtaining an efficient symbiosis with C. glauca. However, others plant species and growth conditions should be tested for a longer period to better optimize the use of Frankia in reforestation programs.