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Xylella fastidiosa biology and ecology

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Presentation on theme: "Xylella fastidiosa biology and ecology"— Presentation transcript:

1 Xylella fastidiosa biology and ecology
Matt Daugherty Department of Entomology UC Riverside

2 vector host pathogen

3 Xylella vectors Xylella host species or varieties Xylella strains

4 Xylella fastidiosa: The early years
Anaheim vine disease -1882 -30, ,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

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

6 First described in Southern California (1882)
Prevalent throughout California, except -mountains -far North? AZ, Gulf states, up to Virginia Costa Rica Brazil Europe

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

8 Mechanism of pathogenicity
1. Vessel occlusion -bacterial aggregates -restricted water flow -water stress symptoms 2. “Phytotoxin” -toxin not known

9 -X. fastidiosa growth depends on temperature

10 Cold mean daily min/max: 17/24°C -mean daily min/max: 21/36°C Hot

11 Overwinter recovery from infection
-depends on timing of inoculation -more recovery in colder climates?

12 Host range 100+ described plant species, from 30 plant families
-most do not host Xylella or show no symptoms -some are susceptible Crops Grape Alfalfa Almond Peach Plum Olive Pecan Pear Coffee Citrus Oleander Sweet gum Oaks Maple Elm Ornamentals /natives Wild/escaped grape Himalayan blackberry Periwinkle Spanish broom Black mustard Weeds



15 -grape varieties exhibit a wide range of symptom severity

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

17 Management in Northern California vineyards
-vector resides in riparian corridor -sweeps seasonally into vineyards -management targets riparian hosts

18 Control is achieved by targeted removal of key hosts for pathogen/vector

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

20 Variation in Xylella pathogenicity
Alm Gr Infection ≠ disease -not all strains cause disease in other hosts -even closely related strains may not be equivalently virulent x Ole Gr x Cit Cof

21 Strain variability for alfalfa dwarf
healthy Strain variability for alfalfa dwarf -alfalfa is susceptible to both grape and almond strains -grape strains are more virulent than almond grape strain healthy almond strain

22 -grape strains produce higher infection rates
-grape isolates cause more severe water stress

23 Proportion transmitting
Transmission depends on: -host plant type -X. fastidiosa strain Determined by infection level Proportion transmitting

24 Disease management 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

25 Disease severity and reservoir status are affected by:
Host plant species or variety X. fastidiosa strain Disease management requires improved knowledge of “problematic” hosts and strain prevalence


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