Screening of Plant Growth-Promoting Bacteria and Biochar for Seed Coat Bioformulation to Enhance Plant Growth Performance

The deterioration of soil quality and rising environmental pollution have substantially undermined agricultural output, thereby endangering global food security. This study examined the impacts of plant growth-promoting bacteria (PGPB) and biochar (BC) -based seed coating on the growth, pigment concentration, and protein content of Vigna unguiculata. Among the isolated strains, PGPB Bacillus cereus SE1Z1 was selected based on its potential to enhance V. unguiculata seedling growth in a roll towel assay. Characterization of SE1Z1 confirmed its key plant growth-promoting traits, such as synthesis of indole-3-acetic acid (IAA), siderophores, and solubilization of P. BC was produced from wood chips and pomegranate peel through pyrolysis at varying temperatures of 400°C, 550°C, and 700°C. The wood chip-derived BC pyrolyzed at 550°C (WCB2) was selected for further studies based on its beneficial effects on V. unguiculata growth and SE1Z1 viability. Evaluation of SE1Z1 and WCB2 -based seed coatings revealed that V. unguiculata seeds treated with either SE1Z1 or WCB2 showed enhanced plant growth, photosynthetic pigments, protein and relative water contents. Notably, the combined application resulted in significantly greater improvements, likely due to synergistic interactions. Furthermore, WCB2 and SE1Z1 coating facilitated higher SE1Z1 colonization in the rhizosphere compared to the SE1Z1 only treatment, indicating that WCB2 may enhance SE1Z1 survival and activity. In conclusion, the integrated use of PGPB and BC as a seed coating presents a promising and eco-friendly approach to improving crop performance.