Download - Phytopathology Modelling. Introduction
General introduction
Phytopathology is the study field of plant diseases caused by pathogens and physiological factors. Plant pathology involves the study of pathogen identification, disease etiology, disease cycles, economic impact, epidemiology, plant disease resistance, effects on humans and animals and disease management.
Phytopathology
keywords
Plant Pathology Plant Pathology : The study of plant diseases: The study of plant diseases
Plant Disease Plant Disease : Any physiological or morphological change : Any physiological or morphological change in a plant that results in abnormal appearance in a plant that results in abnormal appearance
or development or development
Pathogen Pathogen : An organism that causes disease: An organism that causes disease
Host: The infected plantHost: The infected plant
Symptom Symptom : Abnormal appearance of a plant: Abnormal appearance of a plant
Components of a Plant Disease
- Conducive Environment- Conducive Environment
- Susceptible Host- Susceptible Host
- Virulent Pathogen- Virulent Pathogen
- Adequate Time- Adequate Time
TimeTimeDISEASEDISEASE
EnvironmentEnvironment
PathogenPathogen
Susc. Susc. HostHost
Components of a Plant Disease
Disease Classes
- Abiotic- Abiotic (not transmissible)(not transmissible)
- Biotic- Biotic (transmissible) (transmissible)
Causes of Abiotic Diseases
- Environmental (freezing, flooding, drought, light, wind, hail)
-Cultural (mechanical damage, planting problems)
-Chemical (fertilizers, herbicides, pets)
- Physiological Disorders (abnormal growth due to genetic and/or environmental interactions)
Causes of Biotic Diseases (Plant Pathogens)
VirusesViruses
Electron micrograph of purified tristeza virus particles negatively stained with uranyl formate. Bar represents 100 nm
BacteriaBacteria
Pseudomonas syringae bacterial cells on the surface of a bean leaf
(Phaseolus vulgaris)
FungiFungi
Pea Powdery MildewErysiphe pisi
Nematode (Meloidogyne sp. ) captured by a the mycelium of a
fungus at the moment of its penetration in the root
(Root-knot)
NematodesNematodes
Meloidogyne sp. Root-knot namatode penetrating a root
Parasitic PlantsParasitic Plants
Cuscuta campestris, parasitic on Glechoma hederacea. This is one of the most common species of dodder
worldwide.
Schematic representation of some Plant Pathogens
Plant Disease Groups(By Symptoms)
- Leaf Spots
- Leaf and Shoot Blights
- Mildews
- Rusts
- Cankers
- Root Rots- Root Rots
- Wilts- Wilts
- Galls- Galls
- Mosaics and Ringspots- Mosaics and Ringspots
Leaf Spots
Cause: Fungi, bacteria, insects, mites, or abiotic factors
Symptoms:
Circular or “somewhat circular” spots showing chlorosis (yellowing) or necrosis (brown and dead) areas on leaf
Photinia fungal leaf Spot Entomosporium mespili
Leaf and Shoot Blights
Cause: Fungi and bacteria
Symptoms:
Larger areas of leaves (not circular) and shoots showing localized discoloration and/or flagging
Dogwood Anthracnose(Fungal)
Wilts
Cause:Fungi (Verticillium, Fusarium) and Bacteria
Symptoms:Vascular PluggingWilted leaves and shoots
Verticillium WiltSmoke Bush
Dark colored xylem shows vascular plugging
Galls
Cause: Fungi, bacteria, insects, mites, nematodes, and abiotic factors
Symptoms:
Abnormal proliferation of plant tissue Specific to a certain plant organ (leaf, stem, crown or root)
Almond Leaf gallCurl Fungus
Rusts
Cause:Fungi
Symptoms:Fungal spore masses in yellow, orange, white, brown, and black on leaves and stems
Rust ribes host
Fungus requires two host to complete its life cycle. One part on Pinus and the other on Ribes.
Cankers
Cause:Cause:Fungi or bacterial infection resulting in dead, non-Fungi or bacterial infection resulting in dead, non-growing areas on stems and branchesgrowing areas on stems and branches
Symptoms:Symptoms:
Dark, sunken areas with distinct margins on stems Dark, sunken areas with distinct margins on stems sometimes have small red or purple fruiting bodiessometimes have small red or purple fruiting bodies
Same fungi also cause fruit rots (e.g. bulls-eye rot)Same fungi also cause fruit rots (e.g. bulls-eye rot)
Fungal apple Anthracnose
Notice sunken (dead) areas of trunk that have failed to grow and inrease in girth as the rest of the trunk (results in depressed canker)
Root Rots
Cause:Fungi (Armillaria, Phytophthora, Sclerotinia) and bacteria (Erwinia)
Symptoms:Shoot wilting, chlorosis/necrosis
Stem and root discolorationDead roots often with fungal hyphae growth under bark
Tomato (Stem and Fruit Rot)Tomato (Stem and Fruit Rot)
Mildews
Cause:Fungi
Types: - Powdery (common) “Dry” - Downy “Wet”
Symptoms:Chlorosis, yellowing or purple blotches on leaves. White hyphae and fruiting bodies (fuzzy looking) on plant (leaf) surface
Powdery MildewCucumber
Does not like free moisture. Likes high humidity (warm days and cool nights)
Abiotic Plant Disease(Not Transmissable)
Inability to uptake iron from pH neutral or basic soils. Not related to amount of iron (Fe) in soil.
Irregular watering appears as a brown spot at the base of the tomato fruit, this develops into a hard, sunken ring, caused by insufficient calcium flow.
Disease control
-Chemical treatments
-Biocontrol methods
-Development of resistant plant
- Cultural practices: crop rotation, good soil drainage, proper handling of the crop, adequate storage and efficient post-harvest operations
Biocontrol
Bacterial antagonist primary selection
Colletotrichium gloesporoides
Botrytis cinerea
Fusarium oxysporum
Fusarium culmorum
B31
B8
B29
B12
B42B31
B12
B29 B42
B8
B8
B29
B42
B12
B31
T 19°C T 30°CT 25°C
Direct confrontationDirect confrontationTemperature effect on the antagonistic bacterial activity
Perc
enta
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f in
hibi
tion
T…
T…
T…
0
10
20
30
40
50
60
70
80
90
B8 B31 B29 B12 B42
Inh
ibit
ion
de
la
cro
iss
an
ce
myc
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(%
)
Souches abtagonistes
Antagonisme bactérien contre P. tracheiphila
T 19 T25 T30
°c °c °c
Strains
Bacterial antagonisme
Inhibition de la croissance mycélienne par les protéines de la souche B8
A: mycelium growth inhibition ( 70.80% ) by bacterial protein of B8 ( proteins are at 0.356µg /well). B: mycelium development on PDA medium without bacterial extract proteins.
A B
Effet of the proteine treatment on the disease development
00.51
1.52
2.53
3.54
4.55
0 8 15 20 24 28 32 36
T1 T2 T3 T0
Indi
ce o
f th
e di
seas
e
Days
Development of resistant plant
A B
D C
A. in situ initiation of callogenesis from ovules explants by transversal cutted of younger fruits; B. white cals proliferation from ovular explants; C. development of the isolateds cals on MS+NAA; D. green organogenesis cal.
in situ induction and development of ovular cals
A B
A: adventive buds formation from ovular cals on MS+BAP; B: young shoot formation from ovular cals on MS+BAP medium.
Formation of structural organogene cal from ovulair explants
Artificial MS medium.
Dicotylydonary embryos cal obtained from styl explant.
A: Friable cal with embryogenic structures B: Initiation of the rhizogenic structures. D: developed root from friables cals
Organogenesis obtained from no zygotic parts of seeds
A B
C
Plant regeneration from friable cals induced from non zygotic parts of the seeds
A: shoot regeneration on MS+BAP+2,4-D medium; B: young plant regenerated from friable cals; C: Vitroplant de Citrus eurêka developed in vitro on MS medium.
BA
C
- Mal secco : Vasculare disease, Tracheomycosis
- Causal Agent: Phoma tracheiphila (Ciccarone, 1971)
- Hot: Citrus limon
- Geographic distribution:
• Mediterranean sea region
• Black sea costs
Highly contaminated Zones
Lower contaminated Zones
Geographic Distribution of the Mal secco disease
A
D
B
C E
A: Pycnidia of P. tracheiphila on lemon dying shoot; B: Mucilaginous pycnidia gel (the cyrrhus) containing pycnidiospores.
A: Mycelium; B: Pycnidium; C: Phialoconidia; D: Arthroconidia; E: Pycnidiospores
A
B
Total lemon diedback caused by the fungal infection
DisseminationDissemination
• Conidia transportation
- Anemophilous - by water
- Entomophily
• vegetable material exchanges (Homme)
- By birds
Phoma tracheiphila
DPR
DP
RPycnides
Red Pigment
PycnidesAbsence of red pigment
SterileRed Pigment
Types of Types of P. tracheiphilaP. tracheiphila
Morphological varaibility of P. tracheiphila isolates
Isolation of the parasite
Double stranded Eeectrophoretic profil of the Avirulent isolate on agarose gel ( 1 % )
9 kb10 kb
3 kb
1 2 3 4 5
Référence de l’isolat Date de l’isolement Origine géographique Plante hôte Type
V29
2001
Bizerte
Eureka Chromogène
VK 1998 Nabeul lime douce ChromogèneV22 2001 Tunis Eureka ChromogèneV25 2001 Tunis Eureka ChromogèneV23 2001 Nabeul Eureka ChromogeneVH2 2001 Bizerte Eureka ChromogèneVX 2001 Tunis Eureka ChromogèneV4 2001 Tunis Eureka Chromogène
V14 2001 Nabeul Eureka ChromogèneV30 2001 Nabeul Eureka ChromogèneV12 2001 Nabeul Eureka ChromogèneV13 2001 Nabeul Eureka ChromogèneVD 2001 Tunis Eureka ChromogèneVY 2001 Tunis Eureka Chromogène
VH3 2001 Nabeul Eureka ChromogèneV21 2001 Nabeul Eureka ChromogèneV2 2001 Nabeul Eureka Chromogène
VPM 2000 Tunis Eureka ChromogèneV6 2001 Tunis Eureka ChromogèneV7 2001 Nabeul Eureka ChromogèneV8 2001 Tunis Eureka ChromogèneV5 2001 Tunis Eureka Chromogène
V24 2001 Tunis Eureka ChromogèneV26 2001 Tunis Eureka ChromogèneVT1 2001 Tunis Eureka ChromogèneV3 2001 Tunis Eureka Chromogène
VI26 - Italie - ChromogèneV28 2001 Tunis Eureka ChromogèneV66 - Italie - ChromogèneV10 2001 Tunis Eureka ChromogèneV11 2001 Tunis Eureka ChromogèneVI1 - Tunis - ChromogèneV48 - Tunis - ChromogèneV27 2001 Bizerte Eureka ChromogèneVR 2000 Tunis Eureka N. ChromogèneVPt 2000 Tunis Eureka N. Chromogène
P. Tracheiphila collection isolates
Phytosanitary evaluation
- Field infection
- Greenhouse artificial infection
- In vitro artificial infection disease system
Field infection
Empirical scale of evaluation
0 : No drying symptoms
1 : Limited drying to the annual shoots
2 : Drying reach the two years branches
3 : Drying exceeded to the main branches
4 : Trunk drying
5 : Total drying and death of the infected plant
Greenhouse artificial infection
Inoculations MethodsInoculations Methods
Foliar inoculation Stem inoculation Root inoculation
Foliar inoculation
0= No symptoms; 1= Chlorosis on the inoculation point; 2= Chlorosis around the inoculation point; 3= Chlorosis extended till the foliar borders; 4= general chlorosis; 5= foliar necrosis.
Stem and root Inoculation
0= No symptoms; 1= Chlorosis at principal vein of the upper leaves; 2= General chlorosis of the upper leaves; 3= Apical necrosis of the branches; 4= Necrosis extended to the trunk of the inoculated plant; 5= Total necrosis and death of the inoculated plant.
In planta toxin inoculation
In vitro artificial infection disease system
VR
Te
VPt
V11
V21
VH2 V13
Foliar phytotoxicity toxin Test
V13: Isolat de G1
VH2: Isolat de G2
V21: Isolat de G3
V11: Isolat de G4
VR: Isolat de G5
VPt: Isolat de G5
Te: non treated by the toxin
Development of new technic of artificial reproduction of the disease
Parameters:
1- Micropropagated stem necrosis (Fig. a)
0= No symptomes; 1= Necrosis under the 1/3 of the micropropagated stem; 2= Necrosis between 1/3 et 2/3 of the micropropagated stem; 3= Necrosis exceed 2/3 of the micropropagated stem; 4= Total necrosis of the micropropagated stem.
2- Inhibition of the regeneration (Fig. b)
0= No regeneration; 1= Initiation of regeneration; 2= Young shoot; 3= shoot with foliar formation.
20 1 3
ba
Classification of P. tracheiphila isolates