Consortium of plant growth‐promoting bacteria improves spinach (Spinacea oleracea L.) growth under heavy metal stress conditions

BACKGROUND Heavy metal contamination results in oxidative stress to plants and leads to decreased plant growth and development. Affected plants cannot be efficiently used in phytoremediation studies and their potential may be significantly reduced. In many cases, bioaugmentation with plant growth‐promoting bacteria is used as a strategy to alleviate this stress condition. RESULTS Isolates were found to possess 1‐aminocyclopropane‐1‐carboxylate (ACC) deaminase, to produce indole‐3‐acetic acid (IAA) siderophores and to solubilize phosphates, while identification revealed that the isolates belonged to the genera Pseudomonas and Bacillus. Out of the 17 isolates, ten were found to possess ACC deaminase activity, producing 1–3.2 μmol mg−1 h−1 of α‐ketobutyrate and siderophores of catechol and hydroxamate type. A higher quantity of IAA was observed in the case of isolate SGPI 41 (65 μg mL−1). In addition, the inoculation of consortia of isolates led to decreased accumulation of Cd, Pb and Zn in the whole plant but at the same time increased the plant biomass by up to 100% compared with the un‐inoculated control. CONCLUSIONS The use of beneficial bacteria possessing plant growth‐promoting traits is a very useful approach to alleviating heavy metal stress to plants and can be successfully applied in phytoremediation strategies.