Behavior of actinorhizal and rhizobial symbioses under the influence of the same "helper" actinomycetes

SOLANS M, VOBIS G, WALL L.G.

San Carlos de Bariloche, Río Negro, Argenitna

Congreso; 15th International Frankia and actinorhizal plants meeting 2008; 2008

UNQuilmes, UNComahue

The aim of the present study was to examine and compare the effect of saprophytic actinomycetes as ?helper? microorganisms on two different nitrogen-fixing-symbioses: actinorhizal and rhizobial. Experimental assays were carried out under laboratory conditions, employing the strains Streptomyces MM40, Actinoplanes ME3 and Micromonospora MM18, which were previously isolated from the rhizosphere of Ochetophila (=Discaria) trinervis and characterized as rhizoactinomycetic microorganisms. Two symbiotic systems, Ochetophila trinervis-Frankia and Medicago sativa-Sinorhizobium meliloti were used. The corresponding plants were inoculated with the symbiotic strain Frankia BCU110501 and Sinorhizobium meliloti 2011, and coinoculated with the above mentioned rhizoactinomycetes strains. Double inoculations were performed either simultaneously or asynchronously.In both nitrogen-fixing-systems, the nodulation and, consequently the plant growth were significantly stimulated by simultaneously or asynchronously coinoculations with rhizoactinomycetes strains, compared to those plants, which were inoculated only with the symbiotic strains. In spite of the different infection types O. trinervis is infected via intercellular invasion and Medicago sativa L. is infected via root hairs -, apparently the rhizoactinomycetes ?helper? effect on nodulation may operate by a common step in both systems. These results on the rhizoactinomycetes-symbiosis-interaction may open new lines on a topic of potential agronomy application for legumes plants and an ecological role and their possible use on amenity planting and improve the fertility of degenerated forest soil for actinorhizal plants in Patagonia.