Xylella fastidiosa biology and ecology
description
Transcript of Xylella fastidiosa biology and ecology
Xylella fastidiosa biology and ecology
Matt DaughertyDepartment of Entomology
UC Riverside
vector
pathogen host
Xylella vectors
Xylella host speciesor varietiesXylella
strains
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
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
First described in Southern California (1882)
Prevalent throughout California, except
-mountains-far North?
AZ, Gulf states, up to Virginia
Costa Rica
Brazil
Europe
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
1. Vessel occlusion -bacterial aggregates -restricted water flow -water stress symptoms
2. “Phytotoxin” -toxin not known
Mechanism of pathogenicity
-X. fastidiosa growth depends on temperature
Cold
Hot
- mean daily min/max: 17/24°C
-mean daily min/max: 21/36°C
Overwinter recovery from infection
-depends on timing of inoculation
-more recovery in colder climates?
100+ described plant species, from 30 plant families
-most do not host Xylella or show no symptoms
-some are susceptible
Wild/escaped grapeHimalayan blackberryPeriwinkleSpanish broomBlack mustard…
Host range
OleanderSweet gumOaksMapleElm…
GrapeAlfalfaAlmondPeachPlum
OlivePecanPearCoffeeCitrus
Crops WeedsOrnamentals/natives
-grape varieties exhibit a wide range of symptom severity
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
Management in Northern California vineyards
-vector resides in riparian corridor
-sweeps seasonally into vineyards
-management targets riparian hosts
Control is achieved by targeted removal of key hosts for pathogen/vector
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
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
Cit Cofx
x
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
-grape isolates cause more severe water stress
-grape strains produce higher infection rates
Transmission depends on:
-host plant type
-X. fastidiosa strain
Determined by infection level
Pro
po
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ran
smit
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g
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
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
http://www.cnr.berkeley.edu/xylella/
http://xylella.org
http://www.piercesdisease.org/
http://www.cdfa.ca.gov/pdcp/
http://cisr.ucr.edu/