Biocontrol of Trialeurodes vaporariorum by Bacillus velezensis and Bacillus licheniformis through lipopeptide production and induction of tomato defense

The wide application of chemical pesticides has led to various environmental and human health concerns. Biological control is considered an eco-friendly alternative for pest management. This study evaluated the biocontrol effects of the wild-type strains Bacillus velezensis UTB96 and Bacillus licheniformis NBT-192, as well as the codY deletion strain B. velezensis UTB97, against Trialeurodes vaporariorum . The free-choice preference test showed that bacterial treatments reduced whitefly oviposition, with B. licheniformis NBT-192 causing the greatest reduction (91.65% in 8320 and 83.33% in Early Urbana) compared with the control. In the bioassay, B. licheniformis caused the highest mortality of whitefly nymphs and puparium, reaching 51.33%, which was significantly higher than the other bacterial treatments. Bacterial treatments significantly enhanced plant defense responses, including anthocyanin and phenolic accumulation and peroxidase activity. Peroxidase activity increased from 25.90 in control plants to 44.98 following B. licheniformis treatment, while B. velezensis UTB97 produced the highest anthocyanin concentrations (8.545 and 30.303 in 8320 and Early Urbana, respectively). Phenolic concentrations were highest in B. licheniformis -treated plants, reaching 1.117 and 1.180 in 8320 and Early Urbana, respectively. HPTLC analysis revealed that all three bacterial strains produced surfactin, iturin, and fengycin. B. velezensis UTB96 produced the highest levels of surfactin (129.91 mg/L) and iturin (370.55 mg/L), whereas B. licheniformis produced the highest level of fengycin (188.83 mg/L). Bacterial treatments also significantly increased the uptake of N, P, K, Ca, Mn, Zn, Fe, and B, whereas Mg was not significantly affected. Overall, B. licheniformis NBT-192 showed the highest whitefly mortality and was associated with enhanced peroxidase activity, phenolic accumulation, nutrient uptake, and fengycin production, supporting its potential as a biological control agent against T. vaporariorum .