Pseudomonas azotoformans FAP5, a novel biofilm-forming PGPR strain, alleviates drought stress in wheat plant

Abstract

Drought ranks among the most severe environmental stressors that adversely affect crop productivity. Use of stress-tolerant plant growth-promoting rhizobacteria (PGPR) is expected to ameliorate the drought stress in plants. Therefore, in this study, a novel strain, Pseudomonas azotoformans FAP5 with multifunctional traits was obtained from screening of 50 indigenous isolates. The criteria for selection of most promising strain were based on tolerance to water stress, production of PGP traits and biofilm-forming ability in vitro. Further, inoculation response of FAP5 on wheat growth parameters and physiological attributes under different drought conditions was executed under pot experiment. The drought-tolerant FAP5 strain revealed production of exopolysaccharides (EPS), indole 3 acetic acid (IAA), solubilized tricalcium phosphate and exhibited 1-aminpcyclopropane-1-carboxylate (ACC) deaminase (41.58 ± 2.10 μmol α-KB/mg Pr h) activity. ACC deaminase (acdS) and biofilm-associated (AdnA and FliC) genes were confirmed by PCR-based method. Production of PGP traits and biofilm development by FAP5 was exhibited even at water stress condition in vitro. The inoculated wheat plants with FAP5 strain were grown under drought stress showed significant (P < 0.05) improvement in growth attributes, photosynthetic pigment efficiency and other physiological attributes. Similarly, a significant (P < 0.05) antioxidative enzymatic activities in FAP5-inoculated plant were observed compared to uninoculated plants. Under drought stress condition, biofilm development by FAP5 was enhanced significantly and root colonization by inoculant strain was confirmed by viable count and scanning electron microscopy (SEM). The findings indicated that FAP5 strain is effective to drought stress alleviation in wheat plants through various biochemical mechanisms.