Tomato damping-off and root rot are the two most common diseases of tomatoes at the seedling stage. At present, biological compound seed-coating agents are gradually replacing chemical agents in preventing and controlling plant diseases and insect pests, regulating plant growth, and ensuring crop yields. In this study, five biocontrol bacteria (Bacillus amyloliquefaciens (Ba), Bacillus subtilis (Bs wy-1), Bacillus subtilis (WXCDD105), Pseudomonas fluorescens (WXCDD51), and Bacillus velezensis (WZ-37)), with broad antibacterial spectra were mixed with auxiliary factors (inactive components of seed-coating agent) after fermentation to compound a seed-coating agent. In this study, the formula for a compound seed-coating agent was selected through orthogonal experiment. Gaseous silica was used as a thickener, and gum arabic and sodium dodecylbenzene sulfonate were used as a film-forming agent and dispersant, respectively. The mass of fumed silica, gum arabic, sodium dodecylbenzene sulfonate, and pearlescent powder was 1.3 g, 1 g, 0.05 g, and 0.5 g, respectively. Adding gibberellin can improve the ability of seed-coating agents to promote seed germination and plant growth. This showed high efficiency in preventing and controlling seedling diseases and promoting seedling growth. After 6 days of inoculation with Pythium aphanidermatum, which caused tomato damping-off disease, the seedling mortality rate was 26.7% lower than that of the sterile water control, and 20% lower than that of carbendazim. After 21 days of inoculation with Fusarium sp., which caused tomato root rot disease, the seedling mortality rate was 44.31% lower than that of the control, and 22.36% lower than that of carbendazim. The plant height, stem diameter, root length, fresh weight, and dry weight of tomato seeds treated with biological compound seed-coating agent were significantly higher than that of the control. We tested the shelf life of the biological compound seed-coating agent, and found that the effect of seed germination and radicle growth did not decrease. This research provides information on the production technology and application of biological seed-coating agents in tomato production.
Keywords: biocontrol bacteria; biological compound seed-coating agent; root rot disease; tomato damping-off disease.