Abstract text: Root infecting vascular pathogens such as Fusarium oxysporum (Fo) compromise plant performance by invading the xylem and disrupting long distance transport. However, early host responses occurring before vascular colonization remain poorly understood. Here we show that Fo triggers a rapid, systemic, abscisic acid (ABA)–dependent developmental reprogramming in Arabidopsis roots that precedes xylem invasion and involves extensive cell wall remodeling. Initial contact with Fo elevates ABA levels in the root, activating signaling pathways that alter meristem organization, inhibit root growth, and reconfigure vascular patterning. This includes modulation of MIR165/PHB and VND7 networks, leading to premature xylem differentiation and secondary wall deposition. Mutants defective in endodermal ABA signaling (ELTPp::abi1 1) or secondary wall cellulose synthesis (cesa4) display constitutive xylem abnormalities and enhanced resistance to Fo, indicating that ABA driven vascular and cell wall remodeling contributes to restricting pathogen progression. Consistently, Fo infection induces pectin demethylation in the stele—a modification associated with increased wall stiffness and reduced pathogen spread—which is also constitutively present in ELTPp::abi1 1 roots. Together, our findings reveal that ABA mediated vascular plasticity and targeted cell wall modification form an early, developmentally encoded defense strategy that limits Fo invasion and offers new avenues for engineering crop resilience.