Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2016
Publication Date: 12/2/2016
Citation: Sisterson, M.S., Stenger, D.C. 2016. Modeling deployment of Pierce’s disease resistant grapevines. CDFA Pierce's Disease Control Program Research Symposium. p. 192.
Technical Abstract: Deployment of Pierce’s disease resistant grapevines is a key solution to mitigating economic losses caused by Xylella fastidiosa. While Pierce’s disease resistant grapevines under development display mild symptoms and have lower bacterial populations than susceptible varieties, all appear to remain hosts of X. fastidiosa. As resistant grapevines are anticipated to maintain yield after infection, resistant grapevines are less likely to be removed after infection than susceptible grapevines. Accordingly, there is a risk that vineyards planted with resistant grapevines may become sources of X. fastidiosa. To assess risk of resistant varieties serving as a source for pathogen spread to susceptible varieties, a coupled-differential equation model was developed. The model tracked spread of an arthropod-transmitted pathogen in a plant population consisting of a mixture of resistant and susceptible plants. To analyze the model, infection of susceptible plants was separated into two components: spread among susceptible plants and spread from resistant to susceptible plants. Analytical manipulation of the model identified a threshold acquisition rate from resistant plants that resulted in limited pathogen spread from resistant plants to susceptible plants. Acquisition rates from resistant plants that resulted in limited spread to susceptible plants depended on assumptions regarding vector abundance, vector turnover (mortality), removal of infected susceptible plants, and proportion of plants that were resistant. Thus, acquisition rates from resistant plants that result in limited spread to susceptible plants depend on management practices. Simulation of the model determined that effects of deploying a resistant variety on disease incidence in the susceptible variety depended on the extent to which pathogen spread among susceptible plants was controlled (by means other than resistance) and acquisition rates from resistant plants. Deployment of resistant plants that were poor acquisition sources generally resulted in lower disease incidence in the susceptible variety, whereas deployment of resistant plants that were good acquisition sources generally increased disease incidence in the susceptible variety. Results support quantifying acquisition from resistant varieties prior to deployment to determine if additional management is needed to limit spread to nearby vineyards cultivating susceptible varieties. As the model framework was general, additional refinement of the model to consider specific regions, grape cultivars, and vectors in California could provide additional insight.