Phytopathogenic Bacteria

Cuppels Biology 4218a

Disease Diagnosis and Identification of Phytopathogenic Bacteria

Bacterial streaming

• Internal/external symptoms• Culture bacteria and characterize:

morphologygrowth on selective mediachemical compositionnutritional testsenzyme productionserological testsmolecular tests (PCR, etc)pathogenicity tests


BACTERIADIVISION: GRACILICUTES CLASS: PROTEOBACTERIAFamily: Enterobacteriaceae (Gram - ) Family: Pseudomonadaceae (Gram - )

*Erwinia species (Fireblight, soft rot) Acidovorax species (Leaf spot of watermelon,orchids and corn)

Pantoea species (Stewart’s wilt of corn) *Pseudomonas species (Leaf spots, fruit spots, blights, vascular wilts, soft rots, galls)

Serratia species (Yellow vine disease ofcucurbits)

*Ralstonia species (Wilts of solanaceous crops, banana, plantain, peanuts, geranium)

Sphingomonas species (Brown spot of yellow Spanish melon)

Rhizobacter (Bacterial gall of carrot) Rhizomonas (Corky root of lettuce)*Xanthomonas species (Leaf spots, fruit spots,

blight, vascular wilts, citrus canker)

Family: Rhizobiaceae (Gram - ) Family: still unnamed

*Agrobacterium (Crown gall of dicots) Xylella (Leaf scorch and dieback of trees and vines)

Xylophilus species (Bacterial necrosis and canker of grape)

Kingdom Procaryotae

Overview of the primary genera of phytopathogenic bacteria:

* = The six most studied genera of phytopathogenic bacteria


BACTERIADIVISION: FIRMICUTES** CLASS: FIRMIBACTERIA (single-celled)

Bacillus (Tuber rot)

Clostridium (Tuber rot, wetwood of elm and poplar)

DIVISION: FIRMICUTES** CLASS: THALLOBACTERIA (branched)Arthrobacter (Bacterial blight of holly)*Clavibacter (Bacterial wilts in potato, tomato, alfalfa; ring rot of potato)Leifsonia (Ratoon stunting of sugarcane)Rhodococcus (Fasciation of ornamentals and sweet pea)Streptomyces (Common scab of potato)

MOLLICUTESDIVISION: TENERICUTES CLASS: MOLLICUTESFamily: Spiroplasmataceae

Spiroplasma (Corn stunt disease, citrus stubborn disease)

Family: still unnamedPhytoplasma (Yellows diseases, decline diseases in trees, proliferation disease)

** Please note that Firmicutes are Gram-positive


BACTERIADIVISION: GRACILICUTES CLASS: PROTEOBACTERIA

Family: Enterobacteriaceae (Gram -)*Erwinia species

Fire blight, soft rot (most common on fleshy vegetables and fruit)Pantoea species

Stewart’s wilt of corn…spread by corn flea beetles Serratia species (fastidious, phloem-inhabiting)

Yellow Vine Disease of Cucurbits…spread by squash bugSphingomonas melonis

Brown spot of yellow Spanish melon fruit

Erwinia, Oregon State Univ. Bacterial ooze from infected apple, Van der Zwet, USDA

Erwinia carotovora supsp. atroseptica Blackleg of potato,S. DeBoer, CFIA, PEI


Fire blight of apple in Michigan

photo by M. Longstroth, Mich. State Univ.

This picture was taken in early June of 2000, 2 weeks after a hail storm and onset of widespread fire blight symptoms in the region. New shoots have been killed and the leaves have died giving the trees a brown appearance. Both 'Gala' and the M9 rootstock are very susceptible to fire blight.


Bacteria overwinter on margins of old cankers

Young tree heavily infected with fire blight

Twig killed by fire blight

Bacteria in exudate carried by insects and rain

Bees carry bacteria to flowers

Formation of new cankers on branches and stems

Intercellular multiplication in bark

Infected flowers shrivel and die

Infected bark cells collapse

Bacteria penetrate flowers then multiply and spread rapidly

Bacteria travel in xylem and between cells

Disease cycle of fire blight of pear and apple

[from Plant Pathology, 5th ed, G. Agrios]

Infection of young twigs

Infection spreads



Family: Pseudomonadaceae (Gram - )*Pseudomonas species (Leaf spots, fruit spots, blights, vascular wilts, soft rots, galls)

Fluorescent-RNA Grp I-PHB (-)

Examples: marginalis and syringae

fluorescent bacterial growthbiology.uwsp.edu

P. syringae pv. tomato bacterial speck of tomato

P. marginalis on lettucewww.ctahr.hawaii.edu/nelsons


Phytopathogenic Pseudomonas sp. continued

Non-Fluorescent- RNA Grp II- PHB (+)

Examples: cepacia, gladioli

Now is Burkholderia cepaciain Burkholderiaceae

Sour skin on onion www.apsnet.org

http://www.apsnet.org/education/feature/BurkholderiaCepacia/“ Friend or Foe?”

http://www.apsnet.org/education/feature/BurkholderiaCepacia/


Ralstonia solanacearum:

Geranium wilt: race 3 www.agf.gov.bc.ca

Potato brown rot

Moko Disease, www.tpp.uq.edu.au


Family: Pseudomonadaceae (Gram - )*Ralstonia species (Wilts of solanaceous crops, banana, plantain, peanuts, geranium)


Yellow pigment (brominated aryl-polyenes)

Xanthan gums

Monotrichous flagellation

Host-specific


Family: Pseudomonadaceae (Gram - )*Xanthomonas species (Leaf spots, fruit spots, blight, vascular wilts, citrus canker)

X. gardneri , tomato pathogenon nutrient broth yeast ext. agar

X. axonopodis pv. citricitrus canker pathogen

Examples:



Family: Rhizobiaceae (Gram - )* Agrobacterium species (Crown gall, hairy root)

A. tumefaciens: Crown gall of apple rootstock A. vitis: Crown gall of wine grapes

A. rhizogenes: hairy root of carrot

A. rubi: galls on blackberry/rasberry


Agrobacterium infection process:

1. Chemotaxis to wound:

2. Plant cells become conditioned and bacteria bind to them:

3. Induction of bacterial vir genes:

wound soil line

Ti plasmid (site of vir genes)

Wound exudates

Ti

Vir A protein

[ bacteria make cellulose fibrilsand Chv proteins ]

bacteria


http://arabidopsis.info/students/paaras/t_dna.htm

Ti Plasmid (~150-250 kb !!)

vir genes (about 35-45 kb) AB

GC

H

D

FE


4. T- DNA processing and transfer to nucleus of plant cell:

Plant nucleus

T- DNA insertion into plant nuclear DNA:

T-DNA

Ti

Vir B transporter core


Genes carried on T-DNA:

I. Genes affecting plant hormones:(oncogenes)

tms 1: Tryptophan monooxygenase (iaaM)tms 2: Indoleacetamide hydrolase (iaaH)ipt: Isopentenyl transferase

II. Genes involved in opine synthesis(will be utilized as food by the bacteria)

Octopine: N2-(1-carboxyethyl)arginine

Nopaline: N2-(1,3-dicarboxypropyl)arginine

Agropine: N2-(1-mannose)glutamine


T- DNA expression in plant cellsresulting in

plant hormone and opine production at the wound site


BACTERIADIVISION: FIRMICUTES CLASS: THALLOBACTERIA (branched)

*Clavibacter (Bacterial wilts in potato, tomato, alfalfa; ring rot of potato)Streptomyces (Common scab of potato)

Clavibacter spp.pleomorphic, mostly rod-likediaminobutyric acid in cell wallusually non-motile

C. michiganensis subsp. sepedonicumRing rot of potato

Streptomyces scabiesspore-formingbranched vegetative hyphaesoil inhabitantsattacks potato and other root vegetables

Common scab of potato


PLANT DISEASES CAUSED BY FASTIDIOUS VASCULAR BACTERIA

Observed in 1972 in the phloem of clover and periwinkle with clover club leaf disease and in the phloem of citrus with citrus greening disease

Observed in 1973 in the xylem of grapes with Pierce’s disease and the xylem of alfalfa with alfalfa dwarf

Citrus greening diseasewww.apsnet.org

Pierce’s disease of grapewww-plb.ucdavis.edu


Fastidious Xylem-inhabiting Bacteria

Small* with rippled cell wallNo flagellaGrows on complex nutritional mediaVector: sharpshooter leafhoppers

entomology.ucdavis.edu

inventabrasilnet.t5.com.br

Example: Xylella fastidiosa (Gram - )Disease: Pierce’s disease of grape

www.apsnet.org

* Cell size = 0.2 - 0.5 x 1 - 4 μm


Small coryneform bacterium No flagellaGrows on specialized nutritional mediaTransmitted by seed cane, farm tools

www.tpp.uq.edu.au

Fastidious Xylem-inhabiting Bacteria

Example: Leifsonia xyli (Gram +, branched thallobacteria)Disease: Ratoon stunting of sugarcane

pinkish discoloration at nodes


Fastidious Phloem-limited Bacteria

Small with rippled cell wallNo flagellaHas not been cultivatedTransmitted by insects…psyllid

Symptoms: stunting of leaves, shoot proliferation, greening of floral parts

Watermelon, squash, pumpkinSquash bug vectorControl: resistance genes

www.apsnet.org

Example : Candidatus liberobacter asiaticus or africanusDisease: Citrus greening or Huanglongbing (yellow dragon)

Example : Serratia marcescensDisease: Yellow vine disease of cucurbits


MOLLICUTESDIVISION: TENERICUTES CLASS: MOLLICUTESFamily: still unnamed

Phytoplasma (Yellows diseases, decline diseases in trees, proliferation disease)

Cannot be cultivatedSmall genome (500-1000 kb)Greater than 200 diseasesPleomorphicFound in phloem sap, insect organsLeafhopper-transmitted

Aster yellowswww.apsnet.org


Can be cultivatedSmall genome (500-1000 kb)Relatively few diseasesHelical to branched filamentsMotile but no flagellaIn phloem sapLeafhopper-transmittedCan live saprophytically

Corn stunt spiroplasma

www.zarzy.com

MOLLICUTESDIVISION: TENERICUTES CLASS: MOLLICUTESFamily: Spiroplasmataceae

Spiroplasma (Corn stunt disease, citrus stubborn disease)

www.apsnet.org

Phytopathogenic Bacteria

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