Xylella fastidiosa: general traits of a recently introduced ancient threat - Stefania Loreti Centro di ricerca per la Difesa e la Certificazione ...
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Centro Difesa e certificazione di Roma
Xylella fastidiosa: general traits of a
recently introduced ancient threat
Stefania Loreti
Centro di ricerca per la Difesa e la Certificazione
Sede di Roma, Via C.G. Bertero 22
May12/05/2021
12, 2021
Centro Difesa e certificazione di Roma The story….
1882 to 1884 - “A mysterious and new vine disease” in south California
1892 – First report of “California vine disease” by N. Pierce
1978 – First isolation: recognized a bacterium as causal agent of the disease (not a
virus as previously suspected)
1987 – Formal description and naming of Xylella fastidiosa* (Xf) to the causal agent
of the disease
*Xylella = associated with the xylematic location in the host
*fastidiosa = associated with the in vitro growth difficulty
In the meantime, almond, oak, elm and other forest essences are infected in
eastern USA
1990s – Citrus Variegated Chlorosis in Brasil
2000s – 1st genome sequencing of a plant pathogenic bacteria
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General characteristics
Centro Difesa e certificazione di Roma
Kingdom: Bacteria
Phylum: Proteobacteria
Class: γ proteobacteria
•Xylem-limited: movement in acropetal direction (but it can move against the xylematic
flow reaching the roots)
• Forms biofilm that may plug the vessels (polisaccarides)
• Transmitted by sap-sucking insect vectors (Cicadellidae, Cercopidae, Cicadidae)
• Trasmitted by infected plants for planting (dissemination at large scale)
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Life style of Xylella fastidiosa
Bucci, 2018
Xf switch its phenotype from planktonic state to the biofilm aggregation
At the biofilm stage Xf is acquired by the insect that promote new infections and
dissemination
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Xylella subspecies
Centro Difesa e certificazione di Roma
Xylella fastidiosa subsp. fastidiosa: International Society of Plant
Pathology Committee on the
grape, alfalfa, almond, maple (and others) Taxonomy of Plant Pathogenic
Bacteria
Xylella fastidiosa subsp. multiplex:
peach, elm, Prunus spp., Vitis, plane tree (and others)
Xylella fastidiosa subsp. pauca:
citrus, coffee, olive (and others)
Within each subspecies, Xf
Xylella fastidiosa subsp. sandyi: strains are further characterized
oleander in sequence type (n.87 in total)
X. fastidiosa subsp. morus:
mulberry, blueberry
X. fastidiosa subsp. tashke: Chitalpatash kentensis
Recognized the subsp. fastidiosa, multiplex and pauca based on DNA–DNA
hybridization and recently confirmed by comparative genomic analysis (Schaad et al.,
2002; Marcelletti and Scortichini, 2016; Denancé et al., 2019)
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Le sequenze tipo di Xylella
New recover of Xylella fastidiosa
In a pest-free area new plant host
Subspecie and ST characterizations
Presence of possible RECOMBINATIONS among strains
• drive the evolution and adaptation of Xf to new plant hosts
• provide information on the possible origin of the strains
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May 12, 2021
Symptoms: hydric stress
Host range >> EFSA report 2020: ”595 plant species, 275
Centro Difesa e certificazione di Roma
genera and 85 families
Wilting of twigs and branches
Leaf scorch
Donato Boscia CNR, IPSP Bari
John Hartman, University of Kentucky
Donato Boscia CNR, IPSP Bari
Edward L. Barnard, Florida
Department of Agriculture
and Consumer Services
https://gd.eppo.int/taxon/XYLEFA/photos
Stunting, dwarfing Dieback and death of plants
Stefania Loreti, CREA-DC, Roma Donato Boscia CNR, IPSP Bari
May12/05/2021
12, 2021
Symptoms
Centro Difesa e certificazione di Roma
A
Symptoms of hydric stress are due to:
• bacterial cells aggregation, E. W. Kitajima (ESALQ/USP/Brazil)
esopolysaccarides matrice production
and BIOFILM formation (A) B
• overproduction of defence compounds
(pectins), tyloses, produced by the host
plants in response to infection (B)
• air bubbles forms following insect bites Sun et al., 2007 Rapicavoli et al., 2017
and water stress (embolism) C
• amorphous gels coating xylem vessel
walls, presumed of plant origin(C)
Rapicavoli et al., 2017
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Pierce disease of grape
Centro Difesa e certificazione di Roma
Leaf schorching Grape dessication
Irregular
spots on
vegetation
Death of
the plant
Not lignified tissues (green) on lignified branches
Xff/grape: US$105
million/year for losses
and prevention
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Citrus Variegated Chlorosis
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General aspect: reduced vigor
internerval chlorosis
fruits: size reduction, early
ripening, high sugar
content, leathery
internode shortening, desiccation distal portions consistency
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12, 2021‘Phony peach’
Centro Difesa e certificazione di Roma
reduced development;
shortened internodes,
increased lateral
branching; darkening of
leaves
early flowering
reduced fruit size and
early ripening
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12, 2021Leaf schorching/crespera of coffee
Centro Difesa e certificazione di Roma
Internode shorting
Leaves scald
«crespera»
curling of leaf
margins, chlorosis
and deformation
(asymmetry)
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12, 2021Leaf schorching
Centro Difesa e certificazione di Roma
Foto D. Boscia, IPSP
12/05/2021Latent phase
Centro Difesa e certificazione di Roma
Many infected plant remain asymptomatic with consequences on epidemiology,
surveillance and management of the disease
The length of the asymptomatic latent phase varies according to the bacterial strain
and the host
Xf subsp. fastidiosa /grape: 2-3 months
Xf subsp. multiplex /Polygala myrtifolia: 3-4 months Symptoms
appearence
Xf subsp. pauca / Polygala myrtifolia > 6-9 months following artificial
infections
Xf subsp. pauca / Citrus spp.> 8-12 months (Denancé et al., 2017; Saponari, 2018)
Xf subsp. pauca /olive > 14 months
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12, 2021Distribution
Centro Difesa e certificazione di Roma Regulation (EU) 2019/2072 Annex II part B
(Pests known to occur in the union territory)
EPPO A2 list
https://gd.eppo.in
t/taxon/XYLEFA/
distribution
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12, 2021Distribution of subspecies
Centro Difesa e certificazione di Roma
Xylella
taiwanensis
Xff /Xf subsp. fastidiosa
Xfp / Xf subsp pauca
Xfm / Xf subsp. multiplex
Xfs / Xf subsp. sandyi
May12/05/2021
12, 2021Xylella fastidiosa subspecies
Centro Difesa e certificazione di Roma
X. fastidiosa (Xf) subsp. fastidiosa (Xff) e
subsp. sandyi (Xfs) originate from Central
America and were introduced in the USA
in 1890 (Xff) and 1980 (Xfs) respectively
Xf subsp. multiplex (Xfm): a Xfm strain
was introduced from the USA to Brazil
(1930) where it would recombine with a
native strain Xf subsp. pauca (Xfp)
generating the current strains responsible
for the CVC and the coffee leaf scorching
Another divergent strain from Xfp
responsible of CVC and coffee leaf
schorch is that one able to cause the
OQDS in Apulia region
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12, 2021Centro Difesa e certificazione di Roma
2012 – Europe: interception of contaminated plants
2013 - Italy (Apulia)
2015 - France (Corsica, mainland)
2016 - Spain (Baleari, mainland)
2018 – Portugal, Italy (Tuscany)
Outdoors infections of Xf: groves, crossinterland
scape, orchards
2018 – Belgium, Holland, Germany
Interception in indoors (i.e. nurseries)
2013 -Taiwan/grape
2014 - Iran / grape, almond
2017-2018 Israel / almond
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12, 2021Europe distribution of Xf
Centro Difesa e certificazione di Roma
multiplex-ST6, ST7
pauca-ST53
multiplex-ST87
multiplex-ST6, ST7, ST79
sandyi-ST76
pauca-ST53
multiplex-ST7 multiplex-ST6
multiplex-ST81
multiplex-ST7, ST81
fastidiosa-ST1
pauca-ST80
multiplex, 87
Adapted from https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5357 12/05/2021Distribution in Europe and plant-hosts
Centro Difesa e certificazione di Roma
Various ornamental and
Various ornamental and
Mediterranean scrub
Mediterranean scrub
species :
species :
Calicotome, Cistus,
Calicotome, Cistus,
Polygala myrtifolia,
Polygala myrtifolia, Various ornamental and
Lavandula spp., Spartium
Lavandula spp., Spartium Mediterranean scrub
junceum, Helichrisum,
junceum,Rosmarinus…. species :
Rosmarinus,
Polygala myrtifolia,
Almond, olive, peach, elm Lavandula spp., Spartium
trees junceum, Acacia,
Rosmarinus….
Various ornamental and
Mediterranean scrub species Olive, oleander, cherry,
Lavandula dentata, Cytsus scoparius, almond trees..
Coprosma repens, Rosmarinus
officinalis
Various ornamental and
Mediterranean scrub species
(Rhamnus, acacia,olivastro
oleandro…)
Almond, olive, cherry, fig, grape,
walnut trees
Adapted from: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5357 12/05/2021Evolutionary correlations between
European / American subspecies
X. fastidiosa subsp. multiplex was original of Southeastern USA
Strains from California, Europe and Brasil are a consequence of different
introductions events
X. fastidiosa subsp. multiplex in Europe seems to be introduced from California
Recently five different introductions has been individuated in Europe:
Italy (ST87)
Corsica (ST6 and ST7)
Spain- Balearic island (ST81) subsp. multiplex
Spain- Alicante (ST6)
Limited recombination among European isolates indicates that they belong to a
relatively recent group (recent introduction) (Blanca et al.)
The introduction of X. fastidiosa subsp. pauca in Apulia seems to be linked to a
single introduction event from Costa Rica and also in this case the introduction
seems relatively recent (Giampietruzzi et al.)
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May 12, 2021Thank you for
your kind
attention!
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