FRANKIA SP INFECTS ATRIPLEX CORDOBENSIS - CROSS-INOCULATION ASSAYS AND SYMBIOTIC EFFICIENCY

Atriplex cordobensis is an important perennial forage shrub in dry and salt-affected soils of Argentina, has a high leaf N concentration. We found its roots infected with Frankia sp (a N-2-fixing Actinomycete). We isolated an endophyte which could reinfect its host and fix N-2. A triplex cordobensis could also be nodulated by two Frankia strains iso lated from two Rhamnaceae (Colletia spinosissima and Ceanothus america nus), one strain isolated from an Elaeagnaceae (Hippophae rhamnoides) and one atypical strain isolated from Sasuarina equisetifolia, which d id not nodulate its host of origin but nodulated Elaeagnus angustifoli a. All strains used were effective, the least effective being the atyp ical strain from Casuarina equisetifolia. One strain (which had been i solated from Ceanothus americanus) actively fixed N-2, significantly i ncreased the dry weight of the host plant, but did not increase the N concentration in the plant, which was similar to that of the uninocula ted control plant. The Frankia strain isolated from Atriplex cordobens is was therefore assessed to belong to the Elaeagnaceae-Rhamnaceae cro ss-inoculation group.