Fluid dynamic simulations at the interface of the blue-green sharpshooter foregut and grapevine xylem sap with implications for transmission of Xylella fastidiosa

Xylella fastidiosa is a multi-continental, lethal, plant pathogenic bacterium that is transmitted from plant to plant by sharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae) and adult spittlebugs (Hemiptera: Aphrophoridae). The bacterium forms biofilms in plant xylem and the functional foregut of the vector. These biofilms serve as inoculum sources for vector acquisition and inoculation during stylet probing behaviors that accomplish plant-to-plant transmission. In this study, 3D fluid dynamic simulations were performed for bidirectional cibarial propulsion of xylem sap through grapevine xylem and vector functional foregut, using a previously published model of functional foregut anatomy in the blue-green sharpshooter. Results support the hypothesis that X. fastidiosa inoculation primarily occurs by fluid-driven detachment of bacteria from foregut cuticle during egestion, whereas acquisition occurs by a sequential alternation of egestion and ingestion behaviors. These simulation results are supported by previously reported X. fastidiosa colonization patterns in the functional foregut and sharpshooter stylet probing behaviors. Results from this study are directly applicable to development of novel grapevine resistance traits via electropenetrographic monitoring of vector acquisition and inoculation behaviors.