Enhancing Growth of Roselle Plants (Hibiscus sabdariffa L.) Using a Salt- and Drought-Tolerant Rhizobacteria-Soybean Biofertilizer

Salinity and drought stress pose critical challenges to crop productivity, including roselle (Hibiscus sabdariffa L.). Using waste agriculture as a natural source of fertilizer to promote the activity of beneficial soil microorganisms has the potential to help agriculture in abiotic stress-affected areas by increasing plant nutrient uptake and ecological sustainability. We investigate the ability of BioSoy⁺ biofertilizer, which contains salt and drought stress-tolerant plant-growth-promoting rhizobacteria (PGPR) and soybean meal, to improve roselle growth under unfavorable conditions. Rhizobacteria tolerant to salt and drought stress were isolated, and evaluated for growth-promoting traits and pathogen inhibition under stress, and their identity confirmed by 16s rRNA gene sequencing. The impact of BioSoy⁺ on roselle growth and soil stability index during salt and drought stress was evaluated. Salt- and drought-tolerant PGPR strains Pseudomonas nicosulfuronedens AP01 and Bacillus velezensis CC03 were identified as the major component for biofertilizers. Under 2% NaCl stress, Pseudomonas nicosulfuronedens AP01 displayed outstanding phosphate solubilization and robust Sclerotium rolfsii pathogen suppression. BioSoy⁺ biofertilizer application significantly enhanced roselle growth under salt and water-limited conditions. BioSoy⁺ treatment, for example, boosted biomass by 194.74% and 68.29% at 25% field capacity and 100 mM NaCl conditions, respectively. BioSoy⁺ also increased relative water content, microbial activity, proline accumulation, and chlorophyll content, indicating stress reduction and better photosynthetic efficiency. This study highlights the importance of PGPR in alleviating the negative impacts of salt and drought stress. Furthermore, it emphasizes the feasibility of soybean meal as a biofertilizer carrier, fostering sustainable agricultural practices.

Graphical abstract