Influence of arbuscular Mycorrhizae and Rhizobium on free polyamines and proline levels in water-stressed alfalfa

The objective of this research was to study the effect of drought on polyamine and proline levels in alfalfa (Medicago sativa L. cv. Aragon) plants inoculated with a mycorrhizal fungus and/or Rhizobium compared with non-inoculated ones. The four treatments were: a) plants inoculated with Glomus fasciculatum (Taxter sensu Gerd.) Gerdemann and Trappe and Rhizobium meliloti 102 F51 strain (MR), b) plants inoculated with Rhizobium only (R), c) plants inoculated with Glomus only (M), and d) non-inoculated plants (N). Plants were drought stressed during two cycles of moisture stress and recovery. Although proline concentrations increased and free polyamine (spermidine and spermine) contents decreased in leaves and roots of alfalfa under water stress, symbiotic R, M and MR plants maintained higher free polyamine concentrations than non-symbiotic N ones. Results suggest that symbiotic alfalfa plants are better adapted than non-symbiotic ones to cope with water deficit.