Wheat (Triticum aestivum L.) growth enhancement by Azospirillum sp under drought stress

Plant growth promoting rhizobacteria (PGPR) can enhance plant growth by alleviating soil stresses. Although previously investigated, some new interesting details are presented regarding the alleviating affects of Azospirillum sp. on wheat growth under drought stress in this research work. We hypothesized that the isolated strains of Azospirillum sp. may alleviate the adverse effects of drought stress on wheat (Triticum aestivum L.) growth. Three different strains of Azospirillum lipoferum (B1, B2 and B3) were used to inoculate wheat seedlings under drought. During the flowering stage the seedlings were subjected to three drought levels with five different time longevity, including control. Pots were water stressed at 80% (S0), 50% (S1) and 25% (S2) of field capacity moisture in a 25 day-period. Soil and plant water properties including water potential and water content, along with their effects on bacterial inoculum and wheat growth, were completely monitored during the experiment. While stress intensity significantly affected bacterial population and wheat growth, stress longevity only affected wheat water potential and water content. Compared to uninoculated treatments strain B3 (fixing and producing the highest amounts of N and auxin, respectively, with P solubilizing and ACC-deaminase activities) increased wheat yield at S1 and S2 by 43 and 109%, respectively. However, strain B2 (producing siderophore) was the most resistant strain under drought stress. The results of this experiment may elucidate the more efficient strains of Azospirillum sp. for wheat inoculation under drought stress and the mechanisms by which they alleviate the stress.