Binding Bacillus and Pseudomonas in alginate for seed bio-priming strengthens tomato seedlings.

BACKGROUND: Seed biopriming with plant growth-promoting bacteria (PGPB) offers a sustainable strategy to enhance germination and seedling vigor, but its effectiveness is often limited by poor bacterial adherence to seeds. This study evaluated the synergistic effects of combining Bacillus velezensis VRU1 and Pseudomonas chlororaphis VUPF5 with sodium alginate as a biopolymeric binder to strengthen tomato seedlings through seed biopriming. RESULTS: Both bacterial strains successfully colonized tomato roots. Physiological screening revealed complementary traits: B. velezensis produced protease and catalase, whereas P. chlororaphis exhibited lipase, phosphatase, cellulase, catalase, and hydrogen cyanide (HCN) activity. Bacillus velezensis tolerated up to 70 g kg-1 NaCl, and P. chlororaphis tolerated up to 50 g kg-1, indicating salinity resilience. In greenhouse assays, tomato seeds primed with the combined formulation (both strains + alginate) showed significant increases in all growth indicators compared with controls. Correlation analysis and principal component analysis (PCA) identified seedling dry weight as the most influential variable driving treatment efficacy. The alginate matrix enhanced bacterial adhesion, uniform hydration, and controlled release, overcoming a major limitation of conventional bio-inoculants. CONCLUSION: Biopriming with B. velezensis VRU1 and P. chlororaphis VUPF5, using alginate as a binder, significantly improves tomato seedling growth and stress tolerance. This synergistic, eco-friendly approach offers a practical alternative to chemical inputs, with promising applications in sustainable agriculture, saline soil bioremediation, and the development of commercial biofertilizers. © 2026 Society of Chemical Industry.