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Xylella fastidiosa biology and ecology Matt Daugherty Department of Entomology UC Riverside Slide 2 vector pathogen host Slide 3 Xylella vectors Xylella host species or varieties Xylella strains Slide 4 Xylella fastidiosa: The early years Anaheim vine disease -1882 -30,000 - 40,000 acres lost -50 wineries closed Pierce investigated viticulture, climate, epidemiology Vector and pathogen not known -thought to be a virus Isolated, identified as bacterium in 1978 Newton B. Pierce Slide 5 Xylella fastidiosa biology Xylem-limited bacterium Wide host range -crops, native, ornamental, weedy plants -disease severity differs among hosts Substantial genetic variation -host-specific strains -pathogenicity varies among strains Transmitted by xylem-sap feeders -sharpshooters are most important vectors -many sources of variation No cure Slide 6 First described in Southern California (1882) Prevalent throughout California, except -mountains -far North? AZ, Gulf states, up to Virginia Costa Rica Brazil Europe Slide 7 Xylella fastidiosa transmission No latent period Nymphs & adults can transmit -no transmission after molting -persistent in adults Species differ in efficiency Efficiency tied to plant infection level > 10,000 cells/g plant Slide 8 1. Vessel occlusion -bacterial aggregates -restricted water flow -water stress symptoms 2. Phytotoxin -toxin not known Mechanism of pathogenicity Slide 9 -X. fastidiosa growth depends on temperature Slide 10 Cold Hot -mean daily min/max: 17/24C -mean daily min/max: 21/36C Slide 11 Overwinter recovery from infection -depends on timing of inoculation -more recovery in colder climates? Slide 12 100+ described plant species, from 30 plant families -most do not host Xylella or show no symptoms -some are susceptible Wild/escaped grape Himalayan blackberry Periwinkle Spanish broom Black mustard Host range Oleander Sweet gum Oaks Maple Elm Grape Alfalfa Almond Peach Plum Olive Pecan Pear Coffee Citrus CropsWeeds Ornamentals /natives Slide 13 Slide 14 Slide 15 -grape varieties exhibit a wide range of symptom severity Slide 16 Identifying X. fastidiosa reservoirs 1. preferred feeding hosts of vectors? 2. high infection levels? 3. systemic infection? Not known for most landscape and nursery plants Slide 17 Management in Northern California vineyards -vector resides in riparian corridor -sweeps seasonally into vineyards -management targets riparian hosts Slide 18 Control is achieved by targeted removal of key hosts for pathogen/vector Slide 19 Xylella fastidiosa genetic variation Host-plant associated pathogen strains 3+ groupings in the U.S. -grape, almond -almond, oak, peach, plum -oleander Strains are biologically distinct Slide 20 Infection disease -not all strains cause disease in other hosts -even closely related strains may not be equivalently virulent Variation in Xylella pathogenicity Alm Gr Ole Gr CitCof x x Slide 21 healthy grape strain healthy almond strain Strain variability for alfalfa dwarf -alfalfa is susceptible to both grape and almond strains -grape strains are more virulent than almond Slide 22 -grape isolates cause more severe water stress -grape strains produce higher infection rates Slide 23 Transmission depends on: -host plant type -X. fastidiosa strain Determined by infection level Proportion transmitting Slide 24 Landscape management -remove alternative hosts -remove diseased vines (roguing) Develop resistant host varieties -back-crossing with resistant varieties -GMO approach (DSF, or PGIP mutants) Avirulent/symbiotic strains -outcompete X. fastidiosa Disease management Slide 25 Disease severity and reservoir status are affected by: 1.Host plant species or variety 2.X. fastidiosa strain Disease management requires improved knowledge of problematic hosts and strain prevalence Slide 26 http://www.cnr.berkeley.edu/xylella/ http://xylella.org http://www.piercesdisease.org/ http://www.cdfa.ca.gov/pdcp/ http://cisr.ucr.edu/