Co-inoculation of biofilm- and exopolysaccharide-producing rhizobacteria promoting wheat development by boosting plant nutrients in a nutrient-limited soil

Abstract

Increasing global land degradation and human population necessitate more agricultural production; therefore, plant cultivation may expand to nutrient-limited areas to meet growing food demands. As an environmentally safe application, plant growth-promoting rhizobacteria have a high potential to promote plant growth under stress conditions. The present study examined the impacts of single and co-inoculations of two high- and two low-biofilm- and exopolysaccharide (EPS)-producing Bacillus (B) and Azotobacter (A) strains on wheat growth in nutrient-limited soil. High- and low-biofilm-/EPS-producing strains were designated as + ve and − ve, respectively. Among the treatments applied, high-biofilm- and EPS-producing B (−) A (+) and B (+) A (−) treatments significantly enhanced shoot length by 20.4–24.5%, shoot fresh weight by 22.2–27.4%, root length by 31.4–37.1%, root fresh weight by 31.9–34.8%, and root dry weight by 27.2–31.4% over the non-inoculated control. Such two treatments also increased the uptake of nutrients (Ca, K, Mg, Fe, Cu, Mn, and Zn) by the roots more than almost all the other applications. A higher nutrient uptake enhanced the leaf chlorophyll contents and decreased antioxidant enzymes (catalase and peroxidase) activities in wheat seedlings exposed to the respective two treatments. The synergy between co-inoculated bacterial strains and their high-biofilm-/EPS-producing potential in B (−) A (+) and B (+) A (−) treatments appear to have a better role in enhanced wheat growth under nutrient stress by improving plant nutrient availability. The consortium of high-biofilm- and EPS-producing rhizobacteria may be used as potential bioinoculants to increase plant growth in nutrient-limited barren soils.