Enhancing beneficial microbe viability and tobacco black shank disease control via sodium alginate–polyethylene glycol–glycerol hydrogel seed coating

Microbial seed coating is an effective and eco-friendly strategy for plant disease management. In this study, we developed a hydrogel-based microbial seed coating agent using a sodium alginate–polyethylene glycol–glycerol (SA–PEG–Gly) matrix loaded with Aspergillus tamarii TPD11 and Bacillus cereus LgD2. The optimal formulation significantly improved seed vigor, shoot and root growth, and showed good compatibility with tobacco biocontrol bacteria. The hydrogel exhibited pH responsiveness, retained moisture for 60 h, and maintained > 6 log CFU/mL viable cells with stable pH during six months of storage. It achieved > 83 % encapsulation efficiency, preserved antibacterial activity, and sustained viable bacterial populations at 10⁶ CFU/g in soil. Upon application, each coated seed delivered > 3 log CFU of biocontrol agents, promoting tobacco seedling growth and enhancing leaf antioxidant enzyme activities (SOD, POD, CAT). The coating provided > 50.71 % control efficacy against tobacco black shank disease. These results demonstrate the feasibility and potential of the SA–PEG–Gly hydrogel as a carrier for microbial seed coatings, offering a practical and sustainable solution for plant protection and growth promotion. • Developed SA–PEG–Gly hydrogel coating delivering Aspergillus tamarii TPD11 and Bacillus cereus LgD2. • Optimized formulation preserves > 6 log CFU/mL viability during 6-month storage. • Increased seed germination, vigor, and antioxidant enzyme activities in tobacco.