This paper evaluates the possible use of liquid preservation methods for rhizobia long term conservation under ambient temperature conditions. Saline solution (sterile distilled water + NaCl), glycerol and carboxymethycellulose (CMC) were evaluated for preservation of Rhizobium tropici and Bradyrhizobium japonicum cultures up to 180 days and regarding their capacity to promote common bean (Phaseolus vulgaris [L.]) and soybean (Glycine max [L.]) nodulation. The total population was determined after 0; 1; 7; 15; 21; 30; 60; 90; 120; 150 and 180 days of conservation and conserved bacteria were evaluated for symbiotic characteristics after 15, 60 and 120 days of conservation. Although there were significant species x conservation method interactions, both saline solution and CMC may be used for short storage terms, allowing the production of inoculant for field experiments, and its test for purity and concentration before field establishment. The utilized techniques have low cost and easier usage as inoculants, compared to the traditional turf-based products, and if determined feasible by further research it could be a low cost addition to the standard microbiological techniques, particularly as working culture preservation media.
Bradyrhizobium; Carboxymethycellulose; Glycerol; Preservation of bacterial cultures
