Biochemical changes by Azospirillum brasilense enhance jojoba rooting under salt stress

Simmondsia chinensis "Jojoba" is an ever-green shrub, cultivated for its valuable liquid wax. This species is a dioecious plant and its sex cannot be phenotypically discriminated before flowering (3-4 years old plants). Therefore, in vitro culture allows mass propagation of jojoba and it may be used as a model system to study saline stress and biofertilization. The aim of this work was to evaluate biochemical changes induced by Azospirillum brasilense on jojoba in vitro rooting subjected to salt stress. Shoots were induced with 24.6 or 49.2 mu M indole-3-butyric acid for 6 days in half-strength Murashige-Skoog medium with Gamborg vitamins and grown in an auxin-free medium supplemented with 0, 40 or 80 mM NaCl for 45 days. Inoculation was performed with 107 cfu of A. brasilense Az39 or Cd strains when shoots were transferred to auxin free medium. Non-inoculated shoots were used as controls. Azospirillum brasilense inoculation significantly enhanced growth and biochemical parameters, pigments, proteins, total sugars, lignin, phenolics and proline of salt-affected jojoba plants. Biochemical changes observed on salt-stressed jojoba plants were mitigated by both A. brasilense strains and could explain the higher tolerance to salinity of inoculated plants.