bacterial disease of nuts and stone fruits

COST 873

Stone FruitNut Health

Central Science Laboratory, York, UK

Scientific Training Mission

Bacterial Diseases of Nuts and Stone Fruits

Marco Scortichini

C.R.A.- Centro di Ricerca per la Frutticoltura, Roma, Italy

3-6 March, 2008

A short survey of the global market of Nut and Stone Fruits

Traditional producers: Turkey, Italy, U.S.A., Spain, France

NUTS

Hazelnut

Emerging countries: Iran, China, Azeirbaijan, Chile

Walnut

Traditional producers: China, U.S.A., Turkey, France,

Italy, Spain

Emerging countries: India, Iran, Chile

Almond

Traditional producers: U.S.A., Spain, Italy, Greece, Turkey

Emerging countries: India, China

Pistachio

Traditional producers: Iran, U.S.A., Turkey, Syria

STONE FRUITS

Peach

Traditional countries: China, U.S.A., Mediterranean

Europe

Emerging countries: northern Africa (very early ripening

cultivars)

Apricot

Traditional countries: Europe, U.S.A., Eastern Asia

Emerging countries: Pakistan

Plum

Traditional producers: China, U.S.A., Serbia, Germany, Romania

Emerging countries: Chile

Cherry

Traditional producers: U.S.A., Turkey, Germany, Italy, Russia

Emerging countries: Iran

WALNUTXanthomonas arboricola pv. juglandis (Walnut bacterial blight)

- Worldwide distributed

- Limiting factor

- Difficult to control

- Different lineages of the pathogen (vertical oozing canker)

Brenneria nigrifluens (Walnut shallow bark canker)

- Worldwide distributed (suspected)

- Increasing importance

- Difficult to control

Brenneria rubrifaciens (Walnut deep bark canker)

- Apparently limited to California, cv. Hartley

Xanthomonas arboricola pv. juglandis

Main features:

- Isolation: easy-to-perform (YDC, GYCA, BS, Tween)

- Pathogenicity tests: need humidity

- Identification: still based on classical techniques

- Characterization: relevant genetic variability (rep-PCR,

AFLP) >>> geographic and/or plant organ structure ??

- Chemical control: copper spray treatments (not always

effective) >>> new compounds

- Occurrence of copper-resistant strains

- Is Xaj pollen-transmitted ?? (just one report)

- Brown apical necrosis (BAN): which role for Xaj ??

Walnut (Juglans regia L.) in Europe and Eastern Asia: adapted to local

environments

Isoenzimes + UPGMA

AFLP + Multiple canonical analysis

Brenneria nigrifluens

Main features:

- Isolation: not easy (typical symptoms but not isolates on plates)

- Isolation media: NSA, Eosin Blue Agar Medium (Difco)

- Pathogenicity tests: need time to reproduce the symptoms

- Identification: classical (urease test: doubtful) + molecular (rep-PCR)

- Molecular diagnosis: improved but to improve (to verify on

naturally infected samples)

A) 350 bp band, rep-PCR/REP

B) 250 bp, minisatellite M13 phage

- Brenneria: associated with trees >>> pathogenic on stressed plants ??

- Fungi play a role(s) in causing the symptoms ??

- Control: is possible ??

Brenneria rubrifaciens

Very limited knowledge: is present in Europe ??

Isolation: YDC (pink colour of the agar, not colonies)

HAZELNUT

Xanthomonas arboricola pv. corylina (Bacterial blight of Hazelnut)

- EPPO Quarantine pest (A2 list)

- Worldwide distributed

- Dangerous on young trees

Pseudomonas avellanae (Bacterial canker and decline of hazelnut)

- Very aggressive in northern Greece and central Italy

- Dangerous on acidic soils

Pseudomonas syringae pv. coryli (Bacterial twig dieback of Hazelnut)

- Known only in Italy and Germany

- Damages to twigs and trunk

Xanthomonas arboricola pv. corylina

Main features:

- Isolation: quite effective on GYCA, YDC (no selective media)

- Pathogeniciy tests: need humidity

- Characterization: to improve (limited number of international strains)

- Diagnosis: still based on classical techniques

- Cycle of disease: still largely unknown (role(s) of cankers, fallen

leaves, pollen)

- Control: to improve

Pseudomonas avellanae

Main features:

- Isolation: easy on NSA, (no selective media), difficult to maintain

- Pathogenicity tests: to perform in early autumn

- Characterization: relevant information (rep-PCR, ITS, MLST)

- Diagnosis: 16S, hrpW (effective, to improve on plant material)

- Control: copper and S.A.R.-related compound (Bion)

- Effective penetration into the tree via leaf scars

- Two different lineages of the pathogen (Italy and Greece)

- Parallel origin of the two lineages in acidic soils ??

- Is P. avellanae present in other countries ?: Slovenija, Croatia ??

MLST Genetic distance + Mantel test

Pseudomonas syringae pv. coryli

- The real distribution is unknwon

ALMOND

Xanthomonas arboricola pv. pruni (Bacterial spot of Almond)


- Emerging in mediterranean Europe

- Present in India, Australia, New Zealand, U.S.A.

Pseudomonas amygdali (Bacterial canker of Almond)

- Reported only in Greece (Crete) and Turkey

Xylella fastidiosa (Almond leaf scorch)


- A threat in California

Agrobacterium tumefaciens (Crown gall of Almond)

- To be checked in the nurseries (rootstocks)

Xanthomonas arboricola pv. pruni

Very limited knowledge about this pathogen on Almond

(only reports on the occurrence)

Pseudomonas amygdali

Xylella fastidiosa

Agrobacterium (Rhizobium) tumefaciens

Prunus webbii: resistant to artificial inoculation

PISTACHIO

Xanthomonas translucens pv. poae ?? (Pistachio dieback)

- Recently reported in Australia

- Oozing of resin, xylem staining in 2-3-years old twigs, decline

- Kochs postulate only partially fulfilled

PEACHXanthomonas arboricola pv. pruni (Bacterial spot of Peach)


- Increasing importance in Europe

- Spreading mainly through latently infected propagative material

Pseudomonas syringae pv. persicae (Bacterial dieback of Peach)


- Still limited to France (eradicated ?), England (?) and New Zealand (?)

Pseudomonas syringae pv. syringae (Bacterial canker and fruit scab of Peach)

- It can cause severe damage to fruits

Xylella fastidiosa (Phony Peach)


- A future threat ?? (global warming + vectors spreading)

Agrobacterium tumefaciens (Peach Crown Gall)

- A problem for the rootstocks

Main features:

- Isolation: sometimes difficult (GYCA, YDC, NA)

- Pathogenicity tests: requires humidity and high temperatures (25-28C)

- Identification: combination of classical and molecular techniques

- Characterization: good results (rep-PCR, AFLP) at strain level

- Apparently restricted genetic variability

- Molecular diagnosis: to improve (sensitivity, specificity, vegetative samples)

A) 934 bp: RAPD specific fragment

- Control: difficult (copper phytotoxicity) >>> other compounds

- Biological control: how much is effective ??

- Statistical models for predicting the epidemics

- Role(s) of cankers (when present) in the cycle of disease

Restricted genetic variability of the host plant

AFLPfAFLP

Pseudomonas syringae pv. persicae

Main features:

- Reported only during the 70s

- Are still there field symptoms of the disease ?

- Not fluorescent on KB medium >>> CSGA

- Ice nucleation-active bacterium

- Predisposing factors: very cold winter, acidic soils, high nitrogen

very heavy soils

Pseudomonas syringae pv. persicae

RFLP + NJ

France

New

Zealand

UK

Pseudomonas syringae pv. syringae

P. syringae pv. syringae

P. syringae pv. persicae

Main features:

- It occurs occasionally but can be very severe

- It occurs early in the season but symptoms can overlap with those incited by

X. arboricola pv. pruni

- Little knowledge on its cycle of disease

- Control: difficult

Xylella fastidiosa

Main features:


- Very aggressive on Grapevine and Citrus spp.

- There are lineages of the pathogen structured on host plant basis

>>>> subsp. ?, pathovars ?

- Isolation: difficult (long time)

- Pathogenicity tests: difficult (long time)

- Diagnosis: excellent for Grapevine (DAS-ELISA)

- Molecular diagnosis: to validate

A) Grapevine: 733 bp, 1,0 kb-EcoRI fragment

B) Citrus: 500 bp, RAPD specific fragment

- Are there vector(s) in Europe ??

- Could be the pathogen associated with other (European) weeds

and insects ??


- A problem in the nursery (GF 305, 677: very sensitive

- Effectiveness of K84 ?

APRICOT

Xanthomonas arboricola pv. pruni (Bacterial spot of Apricot)


- Emerging pathogen on this crop (spreading in Europe)

Pseudomonas syringae pv. syringae (Bacterial canker of Apricot)

- It can cause severe damages and the death of the tree

- Some cultivar (i.e. Aurora) are very susceptible

Pseudomonas viridiflava (Bacterial canker of Apricot)

- It can be associated with P. syringae

Agrobacterium (Rhizobium) tumefaciens (Apricot Crown Gall)

- Problem in nursery

Pseudomonas syringae pv. syringae

Main features:

- It is an emerging disease mainly in temperate, non Mediterranean areas

- High susceptibility of the cultivar, spring frost and light soils are very

important predisposing factors

- Different lineages of the pathogen >>> new pathovar ?

- Control: difficult (as for any fruit tree species)

JAPANESE PLUM

Xanthomonas arboricola pv. pruni (Bacterial spot of Japanese plum)


- It can be a limiting factor for the cultivation

- Very susceptible cultivars

- Emerging disease

Xylella fastidiosa (Plum Leaf Scald)


- Very dangerous in the U.S.A.

Agrobacterium (Rhizobium) tumefaciens (Crown Gall of Plum)

- It is a problem in the nursery

Xylella fastidiosa

SWEET and SOUR CHERRY

Pseudomonas syringae pv. morsprunorum (Bacterial canker of Cherry)

- Endemic in many areas of cultivation

- Increasing in importance

Pseudomonas syringae pv. syringae (Bacterial canker of Cherry)

- Associated with PSM ??

Pseudomonas syringae pv. avii (Bacterial canker of Cherry)

- Associated with wild Prunus avium ??

Pseudomonas syringae complex

Cycle of disease of Pseudomonads

Main features:

- A Pseudomonas syringae complex

- Increasing importance for timber production and nursery

- Some lineages are associated with organs (i.e. buds, leaves, twigs) ??

- Rep-PCR can discriminate PSM race 1 from PSM race 2

- Diagnosis: difficult to find out a specific primer

- Which is the role of spring frost ??

MANY THANKS FOR YOUR KIND ATTENTION !!!

For further pictures:

www.atlasplantpathogenicbacteria.it

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bacterial disease of nuts and stone fruits