Indole-3-Acetic Acid and 1-Aminocyclopropane-1-Carboxylate Deaminase-Producing Bacteria Alleviate Sodium Stress and Promote Wheat Growth

The 1-amino cyclopropane-1-carboxylic acid deaminase (ACC-D) catalyzes the degradation of ACC, the precursor of the stress ethylene (SE), and indole-3-acetic acid (IAA) stimulates the root growth. The object of present research is to assess whether ACC-D and IAA-producing rhizobacteria can increase tolerance of wheat to salinity-sodicity stress. Several IAA and ACC-D bacteria were isolated from saline-sodic soils of southwestern Iran. The six strains of bacteria that have high IAA production ability and five strains that have high ACC-D activity were selected. The ability of IAA production and ACC-D activity under salinity-sodicity stress were decreased. However, two isolated bacteria (Arthrobacter siccitolerans IRAN1 and Bacillus simplex UT1) were able to produce IAA and ACC-D under salinity-sodicity stress. These bacteria significantly increased the aerial dry matter (ADM), root dry matter (RDM) and relative water content (RWC) of wheat growing under salinity-sodicity stress. ACC deaminase and IAA-producing bacteria decreased the ethylene production and increase of the potassium concentration, respectively. Ratio of potassium to sodium in aerial part of wheat was also increased following bacterial inoculation. As a conclusion, selected bacteria alleviate sodium stress by improving RWC and ion homeostasis in wheat.