INVESTIGATING MECHANISMS OF CLIMATE ADAPTATION IN A PLANT PATHOGEN

The goal of this Predoctoral Fellowship research project is to understand mechanisms of climate adaptation in an economically relevant plant pathogen, which directly addresses AFRI Farm Bill priority area #1: PHPPP. Xylella fastidiosa is a bacterial pathogen that infects over 600 plant species in diverse climates globally. In California, genetically distinct populations of grapevine-infecting X. fastidiosa persist from warmer regions in the South Central Valley (Bakersfield) through regions with cold winters in Northern California (Hopland). Hopland is at the Northern edge of the grapevine-infecting X. fastidiosa range in California: the bacterium is sensitive to cold winters. Our results from an ongoing field experiment in Hopland indicate that a local strain survives the winter at much greater rates than a non-local strain. To verify that this is local adaptation, we propose using reciprocal transplant experiments (sites in Hopland and Bakersfield) with multiple strains of each genetic cluster to compare overwinter survival rates across site and genetic cluster. Then, using >300 X. fastidiosa genomes, we will build gene-environment association models to identify candidate genes associated with colder climates. We will validate the function of candidate genes by testing knockout strains in planta using field experiments in Hopland. Strain-specific X. fastidiosa data will improve models of disease spread under current and future climate conditions and enable more effecitve policy on control measures (quarantine, pesticide use). Primary Mentor Rodrigo Almeida (UC Berkeley) will advise on scientific training for PD Donegan, who will train several undergraduate assistants, fulfilling multiple areas of the AFRI EWD Program.