Plant pathogenic bacteria
General characteristics
Anton von Leuvenhook: first observation of bacteria
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• Pathogen is the microorganism, which
- can be isolated from the diseased organism, - can be grown in a pure culture
- can infect the original host (with the original symptoms)
- can be re-isolate from the new, infected host
Koch’s postulates (1876)
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• The smallest living organisms,
• Usually one cell, only few micrometer large,
• Shape: coccus, bacillus and spirillum
• Occurre everywhere, constant and important constituents of biosphere
Bacteria
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• Leuwenhook 1683 First observation of bacteria
• Koch 1876: anthrax bacillus: Bacillus anthracis
• Burrill 1879: Erwinia amylovora – bacteria can cause disese of plants (fire blight)
• Erwin Smith: First description of many bacteria
• Pammel 1895: Xanthomonas campestris – from cabbage
• Smith 1896: Pseudomonas solanacearum – from potato
• Smith 1907: Agrobacterium tumefaciens – from fruit trees
Big discoveries in bacteriology
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1950 Zoltán Klement the pioneer of plant bacteriology in Hungary
Among 1600 bacterium genera only about 300 cause diseases on plants
Plant pathogenic bacteria
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• Heterotrophic organisms
• Facultative parasites (usually can be cultured in pure cultures on artificial media)
• Usually contains only single cells
• Complex layer of cell wall
• Shape: bacillus, coccus, spirillum
• Majority Gram negative stained
• Aerobe, seldom facultative anaerobe living style
• No real nucleus, only chromatin, containing DNA
• DNA containing small, round plasmids in the cytoplasm
Main properties of plant pathogenic bacteria
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Living forms of bacteria
• Autotrophs (from the energy supply
independent species, using the carbon dioxide as carbon source), chemotrophs,
photoautotrops
• Heterotrophs (using organic carbon source)
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Main components of the bacterial cell
• Cell membrane (lipid)
• Cell wall (double structures of phospholipids and carbohydrates)
• No independent membrane bound organelles
(cell nucleus, plastids, endoplasmic reticulum)
• Complex cell wall, about 10-20 nm thick,
mucoproteid skeleton, external membranes
• (Gram + and -) groups
• Plant pathogenic bacteria are usually Gram -, (G+
mucoproteid skeleton is loose, or G- is compact) - Inner cytoplasm membrane,
- Periplasmic space (peptidoglucane), - Outer membrane (lipids, proteins, LPS-
lipopolysaccharids)
- Cytoplasm: ribosomes, proteins, nucleic acids, plasmids
- EPS envelope (extra-cellular polysaccharide)
Construction of bacterial cell
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Bacterial taxons
• Gram positive (no outer membrane) e.g. Actinobacteria
• Gram negative (with outer membrane) e.g. Proteobacteria
• Unknown, non classified bacteria e.g. Cyanobacteria
Extracellular structures
• Bacterial cell wall (peptidoglucan)
- Gram + type, thick, contains peptidoglucane and lipoteicnoinic acid
- Gram – type thin, contains only lipopolysaccharides
• Outher capsula (envelope) contains alginate and EPS (extra cellular polysaccharides)
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Genetic material
• No real, independent nucleus (prokaryotic organisms)
• Irregular, round shaped DNAs in the nucleotide zone, only one giant chromosome
• The genome contains about 300 genes with about 4Mbp
Cytoplasmic genetic elements
• Chromatin (chromosome)
• Plasmids: independent round shaped DNA
molecules, coding few proeteins, responsibles for few properties (eg. antibiotic resistance)
• Ribosomes and RNAs, producing proteins
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Transposons
• Special bacterial genetic elements, which can be
translocated randomly from one part of the genome to other place
• Flagellum (plural - flagella) 10-20 nm thick, 20-70 mm long, originated from thy cytoplasm
• Types of flagella:
- atrich (without flagellum);
- monotrich (one): Xanthomonas;
- lophotrich (lot in one side): Pseudomonas;
- amphitrich (on two poles);
- peritrich (around the whole surface) : Erwinia
Movement organelles of bacterial cells
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• Development of colonies is characteristic for the bacteria
• Emerging, round shape, slightly wave like…forms
• Some are producing color substances (stains)
(Corynebacterium michiganense yellow, C. insidiosum blue)
Bacterial colonies
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• Rest (leg) phase, (time of DNS replication)
• Log phase (time of reproduction), 3-4 hrs
• Stationer phase, 24-78 hrs
• Asexual (division by bipartition) and sexual (conjugatio) by the pilus, with DNA
• Decline phase
• Plant pathogenic bacteria reproduce slower than animal ones
Reproduction types
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• Temperature: 2-5 oC minimum, 25-30 oC optimum, over 50 oC will die
• Nutrients: water, carbohydrates, alkali pH.
Autotrophic and heterotrophic type of living. Aerobe and anaerobe types
• Light: Not as sensitives as the animal pathogens. UV light is harmful for DNA
Environmental factors influencing the multiplication
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Characterisation protocol of an unknown bacterium 1.
• Isolation from diseased tissue on nutrient agar
• Separation of colonies
• Pathogenicity experiments on tobacco plants (HR)
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Characterisation protocol of an unknown bacterium 2.
• Testing of bacteria producing HR on tobacco plants
• Physiological and biochemical tests
• Pathogenicity tests
• Ice nucleation tests
• Production of antibiotics
Characterisation protocol of an unknown bacterium 3.
Pathogenicity test
• On young fruits
• On young sprouts
• On intact plants
• On cuttings
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• Gram staining: (1884) pararosaniline (Gentiana violet+ KOH). Generally G-, but Clavibacterium G+
• Morphological properties: shape, form, flagella
• In vitro studies: form, colour of colonies
• Biochemical reactions: nitrate reduction,
carbohydrate utilization, gelatine hydrolysis, gas production etc.
• Pathogenicity according to Koch’s postulates
Identification methods
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Gram (+) staining of bacterial cells
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• Symptoms (macroscopic or microscopic)
• Isolation on artificial media, growing in pure cultures
• Colonies, type of colonies
• Microscopic studies (form, shape, flagella)
• Chemical diagnosis: production of different metabolites
• Phage analysis
• Molecular diagnosis: proteins and nucleic acids
Diagnostic methods
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• Serological methods:
- antigen – antibody relation,
- serological reactions: agglutination (cell level), precipitation (in colloid form), immuno-electron microscopy, immuno blotts etc.
Enyme Linked Serological Assay - ELISA
• Antigens: lipoproteins, flagellin
• Agglutination titre for estimation of taxonomic relation. Polyclonal and monoclonal antisera
Serological diagnosis of bacteria
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Immunodiffusion test with serologically related strains
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Antiserum
Antigen samples
• Extraction of proteins or total nucleic acids
• Separation of proteins or nucleic acids by electrophoresis
• Sequence analysis of nucleic acids by restriction endonucleases (produced by fungi)
• PCR – polymerase chain reaction for amplification of nucleic acids
• Hybridization (Western, Southern, Northern blot)
Molecular diagnosis of bacteria
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• 1915 Twort and D’Herelle – discovery of
bacteriophages by specific lyses of bacterial colonies
• Bacteriophages are viruses infecting bacteria
(Delbrück and Luria): No independent metabolism, nucleoproteins, specific for bacterial genera
• Adsorption, vegetative phase, lyses
Phage analysis
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• Adsorption, penetration of phage nucleic acid into the cell.
Only one phage infects!
• Vegetative phase: New protein synthesis, respiration does not change, division (reproduction) stops
• Biosynthesis of new virions, disruption of cell walls
(production about 10-300 new phages in a single bacterial cell)
• Plaque formation (8-12 hrs). Plaque counting. Specific!
Characteristics of phage infection
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• Mechanical way (through by wounds), through by the stomata and lenticels, etc.
• By seed transmission, from the surface and from the endospermium
• Pollen transmission: Erwinia amylovora
• Vegetative mode: tubers, bulbs, grafting etc.
• Vectors: insects, nematodes, humans etc.
• Water (the most common)
Transmission of bacteria
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• Evolution of bacteria: saprophytic, symbiontic,
parasitic (P. fluorescens - P. tabaci, Agrobacterium- Rhizobacterium relationship)
• Pathogenicity: toxin production, pectinases,
hormones causing hypertrophy or other growth abnormalities
Pathogenicity of plant pathogenic bacteria
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• Infection conditions: pathogen, susceptible plants, favourable environmental conditions
• Infection by wounds and natural openings!
• Starts fom the soil, through plant debrids, seeds, wounds of phloem and xyleme vessels
• Vectors: insects, bees, etc.
• Physiological and developmental stage of plants
Infection conditions of phytopathogenic bacteria
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Living types of bacteria
Autotrophs (autonomous energy supply, species, using carbon dioxide of the air as carbon source), chemotrophs,
photoautotrophs, etc.
Heterotrophs (using organic carbon sources)
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• Archaea – thermophil fossil organisms from about 2,5 – 3 milliard years ago, altered type of evolution. Characterization on the basis of 16S ribosomal RNA
• Bacteria - recent taxon, developed approx. 4 milliard years ago
Bacterium domens
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• Penetration into the intercellular space
• Avoid of defence reactions
• Alteration of host metabolism
• Genetic transfer by plasmids (Agrobacterium)
• Colonization of nutrient reach tissues
• Secondary colonization (soft rots)
Phases of bacterial infection
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• General, non-specific defence reaction
• Specific defence reaction (Hypersensitive reaction, HR) Resistant plant, incompatible - host parasite relation
• Lack of defence reaction (susceptible plant) compatible host – parasite relation)
Defence reactions against bacterial infection
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• Susceptible plant (compatibility)
• Avoid the recognition by EPS
• Inhibition of HR (products of Avr genes do not react with the R genes)
• Water and nutrient supply in the intercellular space
• Alteration of pH (efflux of K ions and influx of H ions)
• Moderate production of oxygen free radicals
• Efflux of glucose into the intercellular spaces
Disease induction (in susceptible host)
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• Rapid bacterial multiplication in the intercellular space (water soaking spots)
• Glucose exhaustion, new bacteria will produced without EPS
• Recognition of bacteria by the host
• Bacterial reproduction stops,
• Bacteria will be killed by the necrosis
• Typical bacterial symptoms will develop (necroses, wilting, yellowing etc.)
Necrobiosis in the susceptible host
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• Induction phase: attachment of bacteria on the cell surface
• Activation of hrp (genes of hypersensitivity and pathogenicity) in the bacterial cell
• Latency phase: introduction of Avr or Vir gene products into the host cell
• Activation of R (resistant) genes of the plant
• Increase and accumulation of reactive oxygen radicals
• Activation of antioxidants and antioxidant enzymes
• Necrotic phase: Active destruction of pathogen
• Programmed cell death (HR)
Specific defece reaction (HR)
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• Characterization by transposon mutagenesis
• Because the spoiled genes of the mutants do not induce HR, their reproduction rate decrease
• Organized in gene clusters 25-30 kb. (in the „island of pathogenicity”)
• Localized in the chromosomes or in plasmids (Ralstonia)
• Incorporation into pathogens will induce HR
• Proteins of the III. rd type of secretion mechanism
Genes of hypersensitivity and pathogenicity (hrp)
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• Hypersensitivity is the hyperergic expression of incompatibility
• During the HR by the rapid death of the host cell the bacteria will also be killed
• In the majority of cases the HR leads to resistance (but itself it is not the resistance, only the
consequence of the resistance)
Hypersensitivity
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• Leaf spots, local necroses (Pseudomonas, Xanhomonas)
• Cankers , wounds (Pseudomonas syringae, Erwinia amlylovora)
• Wiltings (irreversible and reversible) (Ralstonia solanacearum)
• Tuber soft rot (Erwinia carotovora)
• Tumors (Agrobacterium tumefaciens)
• Scab (Streptomyces scabies)
Main types symptoms caused by bacterial infection
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• Local spots, water soaked spots, later necroses
• Necrotic spots on the leaves, stems, flowers and fruits
• Bacterial slime
• Chlorosis (effect of toxins), wilting
• Largr necroses, cankers
• Usually caused by Pseudomonads and Xanthomonads
Necroses, leaf spots
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Water soaking and necrosis (Pseudomonas syringae pv. phaseolicola)
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Photo: S. Kadlicskó
• Cankers of woody plants: Pseudomonas mors- prunorum
• Apoplexy: Necrogenic bacteria, ice nucleation,
exhaustion of glucose in the vascular system, frost injury, necrosis in cambium. Caused by:
Pseudomonas syringae pv. syringae
• Fire blight of apple trees: Bacterial mass blocks the nutrient transport, causing wilting and necrosis on twigs and trunks. Caused by: Erwinia amylovora.
Necroses - Cankers
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Necrosis of fire blight (Erwinia amylovora)
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• Blocking of vascular system (ring necrosis)
• Wilting (sometimes temporary)
• Ralstonia solanacearum wilt
• Curtobacterium flaccumfaciens, P. syringae pv.
phaseolicola, Xanthomonas campestris pv. phaseoli
Wilting
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Wilt caused by vascular block
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Ralstonia
solanaceraum blocks the
vascular system and causes
temporary wilting of potato plants and ring necrosis on tubers
• Tubers of potato, bulbs of onion, cabbage head
• Pectolitic enzymes (pectinases, pectin metylesterases) lisate the tuber tissues
• Pathogenicity depends on the enzyme activities
• Erwinia carotovora group
Soft rots caused by bacteria
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Soft rot of carrots caused by Erwinia carotovora
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Fotos: T. Vigh
Potato soft rot (Erwinia carotovora)
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• Cell and tissue proliferation in Dicots by the transfer of bacterial plasmid DNA
• Crown gall caused by Agrobacterium tumefaciens, A.
vitis
• Pseudomonas savastanoi on oil trees
Bacterial tumors
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Tumors on olive trees (Pseudomonas savastanoi)
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Crown gall caused by Agrobacterium vitis
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• 1875 first report on potato scab
• 1891 Streptomyces scabies
• Formerly independent taxon, recently belongs to bacteria (Actinomycetales, Streptomyces)
• No real nucleus, cell wall does not contain chitin
Actinomyces are bacteria, not fungi!
Plant pathogenic bacteria
Economically important bacterial diseases
Taxonomy of most important bacteria
Class Family Genus
Alpha Proteobacteria Rhizobiaceae Agrobacterium Beta Proteobacteria Ralstoniaceae Ralstonia
Gamma Proteobacteria Pseudomonadaceae Pseudomonas
Xanthomonadaceae Xanthomonas
Enterobacteriaceae Erwinia
Actinobacteria Microbacteriaceae Clavibacter
Curtobacterium
Corineabacteriaceae Rhodococcus
Streptomycetaceae Streptomyces
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• Bacteria (Gram -)
• Phylum: Proteobacteria
• Class: Gamma Proteobacteria
• Order: Pseudomonadales
• Family: Pseudomonadaceae
• Genus: Pseudomonas
• Inside the Pseudomonas genus there are animal-, human- and plant pathogenic species
Taxonomy of Pseudomonas genus
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• Pseudomonas species:
• Pseudomonas syringae: species with wide range of hosts, over 50 different pathovars
• Pseudomonas savastanoi – infects oil trees
• Pseudomonas viridiflava – infects sweet pepper
Plant pathogenic Pseudomonas species
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• Rod shaped, Gram-negative bacterias with polar flagella
• Infect a range of plant species
• Presence of INA (ice nucleation active) proteins
• Infection: wet, cool temperature (optimal 12-25 Co), could be seed-borne, can live as saprophyte
• Pathovars:
- P. s. pv. atrofaciens – infects Triticum aestivum - P. s. pv. pisi – infects Pisum sativum
- P. s. pv. syringae – infect Syringa, Prunus, Phaseolus species
Pseudomonas syringae
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Bacterial necroses on tobacco leaf
Serious disease of tobacco plants
caused by Pseudomonas syringae
pv. tabaci
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Pseudomonas syringae pv. syringae
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• Rapid wilting and necrosis of apricot branches
• Necrosis in vascular system
• Causal agent: Pseudomonas syringae pv. syringae
• Bacteria multiply in vascular tissues, utilizing its sugar content
• Ice nucleating strains cause frost damage and stem necrosis
• Control: removal of infected parts (truncation)
• Pruning not in winter, but in spring
Apoplexy of apricot trees
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Truncated apricot tree after bacterial infection
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Died apricot tree : Apoplexy
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Pseudomonas syringae pv. phaseoli
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• Fluorescent soil borne pathogen infects
tomato (stem necrosis, dark
blotches on pruning sites of the stem), soft rot on sweet pepper, the runner beans etc.
Pseudomonas viridiflava
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Pseudomonas viridiflava infection on sweet pepper
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Photo:Z. Klement
Pseudomonas savastanoi
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• Gram negative bacteria, with rod shaped flagella bacteria grow almost exclusively in plants
• Phylum: Proteobacteria
• Class: Gamma Proteobacteria
• Order: Xanthomonadales
• Family: Xanthomonadaceae
• Genus: Xanthomonas
Taxonomy of Xanthomonas genus
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• Cause a large variety of plant diseases
• Pathovars classification based on the host plant
• Important pathovars:
• - pv. campestris.
• - pv. caroteae
• - pv. juglandis
• - pv. malvacearum
• - pv. pelargonii
Xanthomonas campestris
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• Aerobic. Gram negative, mobile (single polar flagellum)
• Principal hosts: tomatoes, sweet pepper and other Solanaceous plants
• Occurs widely in pepper and tomato growing areas, infects under warmer, humid conditions (above 30 oC)
• Survives in seeds, infested debris, stalks
• In glasshouses seed borne infection
(survive on tomato and pepper seeds for 10 years)
• Disseminated by rain splash, irrigation, handling, aerosols
Xanthomonas campestris pv. vesicatoria
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• Corky spots and
scabs, water soaking margins , black
necrotic lesions on the leaves with
yellow haloes
Symptoms on pepper caused by X. vesicatoria pv. vesicatoria
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Xanthomonas campestris ssp. vesicatoria
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Control:
healthy seed, care in
handling,
phytosanitary measures,
resistant variety
Xanthomonas campestris pv. juglandis
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Ralstonia solanacearum
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• Quarantine, aerobic, Gram-negative, soil-borne bacteria with polar flagella
• One of the most important bacterial pathogen, infects over 250 species of 50 families
• Phylum: Proteobacteria
• Class: Beta Proteobacteria
• Order: Burkholderiales
• Family: Ralstoniaceae
• Genus: Ralstonia
• Host range: potato, tomato, pepper, tobacco, eggplant, banana, etc.
• Symptoms: reversible, later irreversible wilting of the leaves. Bacterial exudates accumulate in the vascular system. Ring necrosis in potato tubers
• Overwinters in diseased plants, plant debris, in seed and tubers. Occurs in surface waters, including rivers.
Can be spread by irrigation , mechanical tools and by seeds
• Infects by wounds. Wilting occurs at high concentration of bacteria in the xylem (EPS)
Ralstonia solanacearum
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Erwinia amylovora
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• Contagious, quarantine, Gram-negative bacteria, causal agent of „fireblight disease” of apple trees, affecting
apples, pears, quinces and other members of family
Rosaceae (Cotoneaster, Pyracanthus etc.), Class: Gamma Protobacteria
• Order: Enterobacteriales
• Family: Enterobacteriaceae
• Infects in warm, wet conditions in spring in blossom time.
Affected areas are dying quickly and tender new shoots and leaves. Bacterial exudates
• Dissemination by rain, honeybees, birds and insects
„Shepherds crook” symptom of fire blight
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Symtoms of late infection caused by Erwinia amylovora
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Secondary infection of fire blight on pear
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• Resistant (?) variety
• Rather difficult. Routine inspection in the orchard
• Removal and burning of infected branches
• Antibiotics are not allowed!
• Chemical control by copper containing fungicides with special care of honeybees
• Quarantine measures
Control of fire blight disease
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Erwinia infection on apple shoots
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Apple shoot necrosis
Canker of apple trees caused by Erwinia amylovora
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Erwinia carotovora
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• Rod shaped Gram negative, peritrichously flagellated facultative anaerobe bacterium
• Class: Beta Proteobacteria,
• Order: Enterobacteriales,
• Class: Enterobacteriaceae
• Causes diseases of many plants
• Infects a wide host range, causing soft rot on carrots, potato, tomato, cucurbits, onion, etc.
• Important as post-harvest pathogen
• Produce proteolitic enzymes (pectinases, cellulases)
Erwinia carotovora on cabbagge
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Erwinia carotovora infection
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Erwinia carotovora on carrot
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Soft rot of paotato caused by Erwinia carotovora
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Potato soft rot
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Test for pectolitic enzymes on potato slices
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Photo: M. Kállay
• Rod shaped, Gram negative soil bacterium with flagella
• Causal agent of crown gall disease
• Ti plasmid is responsible for tumor formation
• Class: Alpha Proteobacteria
• Order: Rhizobiales
• Family: Rhizobiaceae
• Genus: Agrobacterium
Agrobacterium tumefaciens
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• Bacteria chemotactically move to the root cells
• Vir A and transmembrane proteins recognize the cell exudates
• Bacteria synthesize cellular fibrils, anchoring bacteria to the host cell
• Cut out of transfer DNA (T-DNA) from the circular (Ti- tumor inducing) plasmid
• One copy of T-DNA (activated by vir genes) transferred into the plant cells by T pilus
• Incorporation of T-DNA into the plant chromosome
Infection by Agrobacterium tumefaciens
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• Vir genes cut out T-DNA region from Ti plasmid
• Gene of indole acetic acid (IAA) production
• Gene of cytokinin production
• Gene for encoding opines (octopine and nopaline
• Only one copy of T-DNA is exported to the host cell!
Genes in the Ti plasmid transfer (T) DNA
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• Cloning and amplification of a desired gene (DNA) sequences (e.g. in Escherichia coli)
• Incorporation of the cloned DNA into Agrobacterium tumefaciens Ti plasmid (transformed bacteria)
• Agroinfection of isolated plant cells or protoplast by transformed A. tumefaciens
• Transformation of host cells by modified Ti plasmid containing the desired gene
• In vivo culture of transformed cells to plants in tissue cultures
Agrobacterium as gene vector
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Tumor formation on fruit tree
Infection of
Agrobacterium means a natural genetic
transformation, a genetically modified plant!
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Crown gall caused by Agrobacterium
Tumor formation of Agrobacterium vitis
• A. vitis DNA has small
differences in its DNA from A. tumefaciens
•A. vitis causes systemic infection on grapes!
•Properties: similar to
Agrobacterium tumefaciens
•Control: Eradication, sanitary measures
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• Symptoms: root proliferation
• Host plants: fruit trees
• Agent: Agrobacterium rhizogenes
• Contains Ri plasmid responsible for the infection and symptoms
• Control: see A. tumefaciens
Agrobacterium rhizogenes
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• Use of resistant (or tolerant) varieties
• Quarantine measures: Erwinia amylovora, Ralstonia solanacearum
• Agro technical methods: prevention, hygiene, prevention of transmission, soil disinfection
• Chemical methods: antibacterial chemicals (no antibiotics are allowed !)
• Biological methods: antagonistic bacteria, e.g.
Agrobacterium K84 strain produces bacteriocin
against Ti plasmid containing Agrobacterium strains
Control of bacterial diseases
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Agrotechnical and chemical control
• Keep the quarantine rules
• Agro technical methods:
• Proper nutrient supply, isolated propagation, preventive measures to avoid of infection, soil disinfection, forecasting
• Hygienic rules
• Chemical control: bactericides, no antibiotics allowed!
Use of resistant varieties to bacterial infection
Resistant and
susceptible cabbage lines in the
experimental field
Photo: Z. Klement
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• Group of soil-and water-borne, Gram positive
organisms, probably the oldest living organism on Earth
• Domain: Bacteria
• Phylum: Actinobacteria
• Class: Actinobacteridaceae
• Order: Actinomycetales
• Specific group of bacteria, morphologically
resembling to the fungi, because of elongated cells or filaments or hyphae.
Taxonomic position of Actinomycetes
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• Unusual filamentous pathogen, similar to fungi
• Causative agent of common scab of potato and other root crops
• Present in soils of potato growing areas
• Symptoms: russet and pitted lesions, later necrotic areas on the surface, corky tissues
• Gray, spiral vegetative hyphae are fragmented into spores
• Spores survive in the soil, spread through water infect by wounds
Streptomyces scabies
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• A distinct group of plant pathogenic organisms, belonging to the bacteria
• There are living in the intercellular space and in the phloem tissues of the plants
• Its genome contains both DNA and RNA
• Have no differentiated cell wall, only cell membrane
• Therefore, their shape is generally round, but variable (pleomorph), about 100 nm in diameter
• Spread by leafhoppers in a persistent manner
• Diseases can be cured by antibiotics
Phytoplasma
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• 1967 Yoi Doi et al. separation from viruses according to the type of genome (RNA and DNA)
• Propagation in artificial media is not successful
• Two living cycles: in planta and in the vector
• Symptoms: dwarfing, yellowing, deformation of flowers, witches broom, hormonal abnormalities
• Taxonomy: formerly according to the symptoms,
recently: Candidatus, on the basis of 16r (ribosomal) DNA
Most important properties of phytoplasma
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• Now total DNA sequences of two species (AYWB and OY) are known (530-1350 kb), with about 671-754 genes
• Have plasmids (similarly to bacteria)
• There are missing some genes characteristic to bacteria (for de novo amino acid, fatty acid, nucleotide- and ATP synthesis)
• There are depended on the metabolism of their host (plant or leafhopper)
• Membrane transport is affected (no tubulin has found necessary for cell division)
• The most primitive forms of auto replication
• Because of repetitive DNA sequences, horizontal gene transfer is possible (recombination among the
chromosomes and the plasmids)
Special characteristics of phytoplasma
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• Chronic, phloem limited bacterial-like organisms affects approx. 300 species in 38 families (onion, letuce, celery, carrot etc.)
• Symptoms: virescence, chlorosis, stunting, sterility of flowers
• Vectored by leafhopper Macrosteles quadrilineatus
• Control: infected plants should be removed and
eliminated. Control of insect vectors and weeds. No cure possibilities
Aster yellows phytoplasma
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Aster yellows phytoplasma on cabbage
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Stolbur phytoplasma
• The most common phytoplasma agent in Hungary
• Spreads by leafhoppers
• Infects tomato (flower deformation) - green pepper (wilting)
- potato (air bulbs)
- tobacco (flower abnormalities)
- grapes (yellowing, redding, gummy shoots) - and a lot of other plants
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Flower abnormalities caused by stolbur phytoplasma
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Yellowing and formation of new branches of tomato
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Stolbur phytoplasma on tobacco
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Wilt of pepper plants caused by Stolbur phytoplasma
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Aerial bulbs on Stolbur phytoplasma infected potato
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Convolvulus sp. infected by stolbur phytoplasma
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Stolbur infection on almond and Polygonathum
Stolbur infection on white grape
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Matured and non matured grape shoots
European stone fruit phytoplasma
• Infects fruit trees (apricot, peach, plum, etc.)
• Transmitted by leafhoppers in persistent manner
• Control of vector species
• Characterization according to 16S rDNA
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Symptoms caused by European stone fruit phytoplasma
Symptoms caused by European stone fruit phytoplasma
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Clover green pethal phytoplasma
• Phyllody and greening of flowers
• Disseminated by leafhoppers
• No economic importance
• Differentiation on the basis of 16S rDNA
Clower green petal phytoplasma
AZ ELŐADÁS LETÖLTHETŐ: -
Georgikon Kar
Növényvédelmi Intézet
Növénypatogén baktériumok
Dr. Richard Gáborjányi
