Amelioration of water deficiency stress in roselle (Hibiscus sabdariffa) by arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria

Belowground interactions between plant roots, arbuscular mycorrhizal fungi (AMFs), and plant growth-promoting rhizobacteria (PGPR) can improve growth and yield under abiotic stress conditions. A pot factorial experiment based on completely randomized design with three replications was conducted to investigate the effects of AMFs (without inoculation as control, inoculation with Funneliformis mosseae and Funneliformis intraradices) and PGPRs (without inoculation as control Pseudomonas fluorescens p-169 inoculation) on roselle (Hibiscus sabdariffa L.) grown under water deficiency stress (WDS) [90% (I1), 75% (I2), 50% (I3), and 25% (I4) of field capacity as well-watered, mild, moderate, and severe stress, respectively]. The results showed that by applying WDS, the plant growth properties such as root and sepals’ dry weight, 1000-seed weight, seed yield, chlorophyll a, b, and total, carotenoids, and leaf water content was significantly reduced. The application of AMFs and PGPR under WDS conditions increased 1000-seed weight, seed yield. In response to WDS osmotic adjustment were provided in Roselle and under stress conditions. The highest seed yield was found under well-watered treatment by inoculation of F. mosseae without PGPR and the application of Pseudomonas fluorescens (6.37 and 6.51 g/plant, respectively). These results suggesting the antagonistic effects of AMFs and PGPR. AMFs inoculation under severe stress increased sepals dry weight compared to the non-inoculation. In conclusion, increased activity of enzymatic antioxidants and higher production of non-enzymatic antioxidant compounds, as well as photosynthetic pigments in symbiotic association with AMFs, can alleviate reactive oxygen species damage resulting in increased growth and yield parameters and improve water stress tolerance.