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

Abstract

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.