Rhizobacterial Bacillus subtilis Strain IZ-25 induces antioxidant defense and phenylpropanoid pathways to mitigate whitefly (Bemisia tabaci) infestation in tomato

Whitefly ( Bemisia tabaci ) severely constrains tomato productivity by inducing oxidative stress and disrupting carbon metabolism. This study evaluated the potential of Bacillus subtilis IZ-25 to enhance tomato resistance by activating antioxidant and phenylpropanoid defenses. IZ-25 treatment resulted in an 80% reduction in egg numbers and a 77% decrease in adult whiteflies compared to the control. IZ-25 significantly enhanced antioxidant enzyme activities, including a 55% increase in catalase and a fourfold increase in guaiacol peroxidase, accompanied by a 17% rise in ascorbate peroxidase and a 41% reduction in H₂O₂ levels. Phenylpropanoid metabolism was also markedly induced, with phenylalanine ammonia-lyase activity increasing by 22%, and total phenolics, flavonoids, and lignin increasing by 17%, 6%, and 44%, respectively. GC-MS profiling further confirmed that IZ-25 produces bioactive metabolites, including flavonoid-like and triterpenoid/steroidal compounds, which are known to possess insect-deterrent and feeding-inhibitory properties. Pearson correlation and PCA analysis demonstrated strong negative correlations between antioxidant and phenylpropanoid biomarkers and whitefly infestation (r = -0.85 to -0.96). Overall, IZ-25 induced a dual-defense strategy that integrates redox homeostasis, secondary metabolite accumulation, and bioactive compound production, highlighting its potential as an eco-friendly approach to whitefly control in tomato cultivation. Further molecular validation of JA/SA signaling is required to elucidate the comprehensive mechanistic basis of this resistance. • PGPR Bacillus subtilis IZ-25 reduced whitefly ( Bemisia tabaci ) eggs and adult populations on tomato by 80% and 77%, respectively. • IZ-25 strongly enhanced antioxidant defense, increasing CAT, GPX, and APX activities and reducing H₂O₂ accumulation under whitefly infestation. • Phenylpropanoid pathway activation by IZ-25 elevated PAL activity and boosted phenolic, flavonoid, and lignin levels, reinforcing structural and chemical defenses. • GC–MS profiling revealed that IZ-25 secretes flavonoid-like, triterpenoid, and steroidal metabolites with potential insect-deterrent and anti-feeding activities. • Multivariate (correlation and PCA) analyses confirmed that antioxidants and phenylpropanoid biomarkers are the main determinants of whitefly suppression, highlighting IZ-25 as a promising biocontrol agent for sustainable IPM in tomato.