Post on 30-Dec-2015
Bacterial Plant Pathogens
• What are bacteria?What are bacteria?• Bacterial identificationBacterial identification• Generalized disease cycleGeneralized disease cycle• Disease symptomsDisease symptoms• Disease controlDisease control
Bacterial Plant Pathogens
Size (0.3-1.5 x 0.7-5 um )
Generally single celled
Reproduce by simple fission
Prokaryotes
No membrane bound nucleus or organelles
Lack chlorophyll
Most have cell wall
Some are motile – flagellum (a)
Single circular chromosome
Structure
cell shape
colony appearance
motility (flagella)
Identification
Identification
Biochemicalcell wall composition
Identification
Respiration aerobic, anaerobic, facultative
anaerobic
Nutritional requirement (C, N, {Biolog})
Fatty acids {FAME}
SerologyNucleic acids
Identification
Pathogenicity
Plant Pathogenic Bacteria Plant Pathogenic Bacteria (for PLPA3004)(for PLPA3004)
• 8 genera of bacteria, 1 of uncertain 8 genera of bacteria, 1 of uncertain IDID
• 2 genera of Mollicutes (lack cell 2 genera of Mollicutes (lack cell wallswalls
• Approximately 50-60 spp. (200 Approximately 50-60 spp. (200 pathovars {pv.})pathovars {pv.})
• Pathovar – pathogenic on a specific Pathovar – pathogenic on a specific host (crop)host (crop)
Plant Pathogenic Bacteria Plant Pathogenic Bacteria (for PLPA3004)(for PLPA3004)
• Most are facultative parasites, Most are facultative parasites, – Except fastidious bacteria and Except fastidious bacteria and
mollicutesmollicutes
• Most are gram-, rod-shaped Most are gram-, rod-shaped bacteriabacteria
Fastidious vascular Fastidious vascular bacteriabacteria
• Vectored by leafhoppers, except Vectored by leafhoppers, except ClavibacterClavibacter
• Unknown-phloem limited bacterium Unknown-phloem limited bacterium not culturablenot culturable
• Symptoms – stunting, leaf scalding, Symptoms – stunting, leaf scalding, declinedecline
• Xylella – Pierce’s disease of grapeXylella – Pierce’s disease of grape
MollicutesMollicutes
• Lack cell wallLack cell wall• Phloem limitedPhloem limited• Transmitted by leafhoppersTransmitted by leafhoppers• Phytoplasmas – amorphousPhytoplasmas – amorphous• Spiroplasmas - helicalSpiroplasmas - helical• Symptoms – yellows diseases, witches’ Symptoms – yellows diseases, witches’
brooming, stuntingbrooming, stunting• Sensitive to TetracyclineSensitive to Tetracycline
Disease cycle
Overseasoning
2 cycle
Dissemination
PenetrationDiseasedevelopment
Reproductiono
Disease cycle
A. OVERSEASONING
1. Infected or infested seed
2. Infected plant parts or plants
3. Plant residues
4. Alternative hosts
5. Soil
6. Insects
A. OVERSEASONING
1. Infected or infested seed
2. Infected plant parts or plants
3. Plant residues
4. Alternative hosts
5. Soil
6. Insects
Protected environment
Disease cycle
B. DISSEMINATIONB. DISSEMINATIONshort distance
1.Water
2. Soil
3. Tools and equipment
4. Insects
Disease cycle
long distance
5. Insects
6. Storage, shipping containers
7. Movement of infected plant parts (seeds, tubers, bulbs, fruit, transplants, nursery stock)
long distance
5. Insects
6. Storage, shipping containers
7. Movement of infected plant parts (seeds, tubers, bulbs, fruit, transplants, nursery stock)
B. DISSEMINATIONB. DISSEMINATION
Disease cycle
C. PENETRATION (INDIRECT ONLY)
1. Natural openings (stomates, hydathodes, nectaries)
2. Wounds (tools, equipment, insects, hail)
C. PENETRATION (INDIRECT ONLY)
1. Natural openings (stomates, hydathodes, nectaries)
2. Wounds (tools, equipment, insects, hail)
Disease cycle
D. DEVELOPMENT
1. Intercellular
2. Wilts (xylem and surrounding cells)
3. IntracellularPhloem-limited
D. DEVELOPMENT
1. Intercellular
2. Wilts (xylem and surrounding cells)
3. IntracellularPhloem-limited
Disease cycle
E. REPRODUCTION
F. SECONDARY CYCLE
E. REPRODUCTION
F. SECONDARY CYCLE
Disease control
A. Often difficultrapid reproductionoverwinter in protected sitesrapid penetrationreadily disseminatedfew effective chemical controls
A. Often difficultrapid reproductionoverwinter in protected sitesrapid penetrationreadily disseminatedfew effective chemical controls
Disease Control
B. Common controls1. Pathogen free plants
certified seeddisease-free transplants
2. Sanitationdestroy infected materialsincorporate plant debrisclean tools, shipping containers,storage facilities
B. Common controls1. Pathogen free plants
certified seeddisease-free transplants
2. Sanitationdestroy infected materialsincorporate plant debrisclean tools, shipping containers,storage facilities
Disease Control
3. Minimize wounding
4. Control insect vectors
5. Eliminate alternate hosts
6. Disease resistance
3. Minimize wounding
4. Control insect vectors
5. Eliminate alternate hosts
6. Disease resistance
Disease Control
7. ChemicalsStreptomycinKocide (copper containing compounds)
7. ChemicalsStreptomycinKocide (copper containing compounds)
Symptoms
A. Soft rotssoft rot of vegetables (Erwinia carotovora pv. carotovora)
B. Leafspotsbacterial blights of bean (Xanthomonas campestris pv. phaseoli, Pseudomonas syringae pv. phaseolicola)
C. Blightsfireblight of apples, pears(Erwinia amylovora
A. Soft rotssoft rot of vegetables
B. Leafspotsbacterial blights of bean
C. Blightsfireblight of apples, pears
Symptoms
D. Vascular wiltssouthern bacterial wilt of tomatoPseudomonas solanacearum
E. Gallscrown gallAgrobacterium tumefaciens
F. Cankersfireblight of apples, pears(Erwinia amylovora)
D. Vascular wiltssouthern bacterial wilt of tomato
E. Gallscrown gall
F. Cankersfireblight of apples, pears
Symptoms
G. Scabspotato scab(Streptomyces scabies)
H. Mollicute diseasesyellowing, witches brooming, stunting, declineAster yellow MLO
I. Fastidious vascular bacteriaXylem-limited stunting,leaf scalding or scorching, declinePhloem-limited stunting, witches' brooming, greening of flower parts
G. Scabspotato scab
H. Mollicute diseasesyellowing, witches brooming, stunting, decline
I. Fastidious vascular bacteriaXylem-limited stunting,leaf scalding or scorching, declinePhloem-limited stunting, witches' brooming, greening of flower parts