Modelling Xylella fastidiosa Infection Dynamics in Grapevines: A Physiologically Based Approach

Xylella fastidiosa subsp. fastidiosa (Xff), the causal agent of Pierce's Disease (PD) in grapevine, is a major threat to global viticulture. However, the mechanisms governing infection establishment, persistence, and recovery within grapevine hosts remain insufficiently characterized. We developed a novel physiologically based infection model that explicitly describes the population dynamics and within-plant spread of Xff in grapevine plants as a function of temperature and host phenology. Grapevines are represented as structured hosts composed of two interacting compartments: permanent woody tissues and seasonally renewed annual tissues. Bacterial growth, mortality, and translocation between compartments are described using temperature-dependent functions and seasonal variation in tissue availability, allowing the simulation of growing-season dynamics, winter dormancy, pruning, and cold-induced recovery. The model is formulated as a stochastic framework based on coupled Kolmogorov partial differential equations (PDEs), allowing representation of heterogeneity in bacterial loads among infected plants and the probabilistic outcome of chronic infection or recovery. Simulations across different climatic locations and inoculation scenarios reproduced key epidemiological patterns reported in empirical and modelling studies, including seasonal detection dynamics, temperature-dependent establishment of chronic infection, and multi-year infection trajectories. The framework highlights the critical role of interactions between permanent and annual tissues in shaping PD dynamics and provides mechanistic insight into how climate modulates infection persistence. By explicitly linking within-host bacterial processes to local climatic conditions, the model provides a novel tool to explore PD risk, evaluate future climate scenarios, and support the optimization of surveillance and management strategies at fine temporal scale.