Plant Virology
General properties
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• Viruses: Infective genetic informations inside the host cell, parasiting the protein and nucleic acid
metabolism of the host plant
• Bacteria: Microscopic prokaryote (without real nucleus) heterotrophic organisms, living in the intercellular space of the host, with biotroph or necrotroph type of living
• Fungi: Eukaryotic (with real nucleus) heterotrophic organisms, living on the surface or in the intercellular space of the host cells
Main properties of plant pathogenic microorganisms
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Rembrandt and the „Rembrandt tulips”
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Carolus Clusius 1576
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Symptoms of Tobacco mosaic virus (TMV) on tobacco
Adolf Mayer (1843-1942)
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• 1935 Stanley: Tobacco mosaic virus (TMV) paracristals of viruses, with protein nature
• 1937 Bawden and Pirie: Viruses are infectious nucleoproteins
• 1939 Kausche et al., Tsugita et al. : Electron microscopy of TMV virions
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The most important discoveries in plant virology I.
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Dimitrij Ivanovksij (1864-1920)
• Infective nature of tobacco mosaic disease
• Filtration though bacterial sieves
• Longevity experiments
• Foundation of plant virology
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The most important discoveries in virology II.
• 1953 Watson and Crick: DNA helical structure
• 1956 Gierer et al.: Infective RNA from TMV
• 1971 Diener: Discovery of viroids
• 1980 Hirth et al., Hull et al.: Complete primer
structure (nucleotide basis sequence) of Cauliflower mosaic virus (CaMV) DNA
• 1982 Goelet et al.: Complete sequence of TMV RNA
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Works of Watson and Crick
• Structure of DNA (Nobel Prize 1953)
• Paracristals studies on TMV virions
• Construction of TMV model
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Structure of plant pathogenic viruses
• Glycoprotein envelope (rare)
• Protein coat (CP) - protect the genome from physical and chemical injuries
• Nucleic acid genome - Properties are dependent from the nucleotide sequence
- Single stranded DNA (rare)
- Double stranded DNA (about 15-20%) - Single stranded RNA (about 70-80%) - Double stranded RNA (rare)
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Life cycle of viruses
• Inactive virions with regular shape (symmetry)
• Vegetative viruses in the course of virus replication, attached to plant structures
• Virions are usually stored and accumulated in the host cells translocated in the host and spread by vectors
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Viruses are infective nucleoproteids
• Viruses are infective nucleoproteins, containing only one type of genome (DNA or RNA) covered by coat protein subunits
• Virions are not visible by light microscopes, have no own metabolism, are replicated (multiplicated) only in living tissues, there are obligate parasites, using the protein and nucleic acid metabolism of the host cells
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Virion forms and shape
• Isometric, about 12-50 nm large virions, where the nucleic acid is inside of coat protein shell,
constructed according to the rules of isometric crystals
• Helical, about 100- 2000 nm long, rigid or flexible particles, where the nucleic acid forms a helical structure, covered by coat proteins subunits
• In both cases there are exist single component or multicomponent forms (with non-divided and
divided genomes)
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Organization forms of genome
• Non divided (single component) genome: TMV, CaMV
• Divided (multicomponent) genome: Cowpea mosaic virus (CPMV), Brome mosaic virus (BMV)
• Multicomponent viruses are only infective in the
presence of all components because the information of properties are also divided
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Virions of Barley stripe mosaic virus (BSMV)
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Isometric, multicomponent virions of BMV
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Basic groups of viruses
• Double stranded DNA viruses (eg. Caulimovirus)
• Single stranded DNA viruses (eg. Geminivirus)
• Double stranded RNA viruses (eg. Reovirus)
• Single + stranded viruses (eg. Tobamovirus)
• Single – stranded viruses (eg. Tospovirus)
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Morphologycal classification of plant viruses
Bases of classification
• Genome DNA or RNA
• Number of strands
• RNA positive or negative
• Helical or isometric virions
• Genome divided or not
• Glycoprotein envelope
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Diagnostic methods
• Visual symptoms of diseased plants
• Tools: light microscope, electron microscope,
• Pure cultures (in case of viruses: in vivo cultures on living plants)
• Symptoms of test plants (in vivo)
• Biochemical methods (proteins and nucleic acids, other substances of host metabolism)
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Visual symptoms of diseased plants
• Disease diagnosis on the basis of symptoms
• Not always reliable
- same agents exist with different symptoms
- same symptoms can be caused by different agents
• The visual diagnosis always needs the use of
additional diagnostic methods for identification and for the development of control measurements
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Classification of virus symptoms
• Macroscopic (visible) symptoms
- Local symptoms (developed on the site of infection) - Systemic symptoms (developed far from the
infection)
• Microscopic symptoms
- Light microscopic (inclusions)
- Electron microscopic symptoms (inclusions, tissue abnormalities)
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Local symptoms
• Local chloroses
• Local necroses, hypersensitive reaction (HR)
• Starch lesions
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Local chloroses (TSWV)
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Lokális necroses (TMV)
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Incorporation of L genes of pepper results resistance
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Systemic symptoms
• Systemic chlorosis
• Mosaic, stripes, streaks
• Deformations (leaf-, flower-, fruit-)
• Necroses (leaf-, stem-, terminal bud)
• Flower breaking
• Ringspot (leaves, fruits)
• Root proliferation (rhizomania)
• Stunting , dwarfing
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Systemic redding and yellowing (WDV and BYDV)
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Systemic stripes and mosaic (BSMV and MDMV)
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Systemic mosaic (TYMV)
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Pepino mosaic virus
Systemic mosaic (PepMV)
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Rhyzomania symptoms and its vector (Polymyxa)
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Cuscuta species as virus vectors
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Enations (PNRSV)
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Leaf roll symptoms on grapevine leaves (GLRaV)
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Vein clearing symptoms (ApMV)
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Tuber necrotic ring symptoms and veinal necrosis (PVYNTN)
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Distorted leaf development (PNRSV)
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Klorótikus foltok (PepMV)
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Symptoms of plum pox virus on greengage (PPV)
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Plum pox symptoms on apricot stone (PPV)
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Ring spot symptoms on pepper fruits (TSWV)
Foto: Csilléry G.
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Non visible (microscopic) symptoms
• Microscopic symptoms (inclusions, tissue necroses, Igel-Lange test)
• Electron microscopic (transmission- and scanning) symptoms
- Form and shape of virions
- Immuno-electro microscopic studies - Fine structure of virus inclusions
- Tissue abnormalities
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Pure cultures
• Viruses are obligate parasites, therefore it is impossible to propagate them in vitro cultures
• „Pure culture” means in virology a culture of the
virus in a systemic host, originated from a „single cell local lesion
• „Single cell lesion” means a homogenous genetic population
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In vivo studies
• Local lesions (necroses) for quantitative measurement of virus infectivity
• Separation of mixed (complex) infections
• Use of indicator plants in identification process
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Virus purification
• Choose the plant materials and buffers
• Homogenization, filtration
• Clarification with organic solvents
• Centrifugation in slow speed
• Ultracentrifugation
• Solution and precipitation
• Dialysis
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Sucrose gradient ultracentrifugation of multicomponent viruses (CpMV)
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Basic terms in serology
• Antigens (lipids, carbohydrates and proteins with high molecular weights)
• „Epitops”- Specific surface determinants
• Antibodies – Specific proteins (IgG, IgM) with
„paratroph” structures
• Antigen-antibody specific reactions: agglutination, precipitation, immunodiffusion (in agarose,
poliacrylamide gels etc.)
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Rabbit immunization (MDMV)
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Serological reactions
• Agglutination and precipitation
• Immunodiffusion (in gel)
• Immuno-electron microscopy
• ELISA (Enzyme linked immunosorbent assay)
• Immuno-electrophoresis
• Immuno blotting (Western blot, dot blot, tissue blot)
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Agar gel diffuson test (TAV, CMV)
Fotó: Beczner L.
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Use of ELISA for detection of plant viruses
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Methods of molecular virology
• Gel electrophoresis of proteins and nucleic acids
• Detection of proteins (Western blot, immuno blot)
• PCR – polymerase chain reaction
• Determination of nucleotide sequences by restriction enzymes (DNA)
• Hybridization of nucleic acids by labelled nucleic acids after electrophoresis
- Southern blot – DNA (separated
- Northern blot – RNS
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Natural forms of virus transmission
• Mechanical transmission (by wounds)
• Seed and pollen transmission
• Vegetative transmission (tubers, bulbs ect.)
• Vector transmission
- transmission of sucking and chewing insects - nematode transmission
- soil borne pathogens
- parasitic plants (Cuscuta sp.)
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Mechanikai átvitel (inokuláció) sebzéssel
Mechanical transmission (inoculation)
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Mechanical transmission by cultivation
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Spread of tobacco viruses by decapitation
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Grafting
Virus transmission by grafting
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Grafting and its results (RBDV)
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Forms of seed transmission
• Transmission by surface infection (perycarpium).
Infection can be eliminate by surface disinfection
• Inner transmission (endospermium)
Impossible to eliminate the pathogen by surface disinfection or by heat treatment
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Inner seed transnission (BCMV)
Healthy Photo: L. Beczner Infected
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Main groups of vector transmission
• Aphid transmission (eg. Potato leafroll virus, PLRV)
• Leafhoppers (eg. Wheat dwarf virus, WDV)
• Leaf miners (eg. Turnip crinkle virus, TuCV)
• Mites (eg. Wheat streak mosaic virus, WSMV)
• Trips (eg. Tomato spotted wilt virus, TSWV)
• Beets (eg. Potato virus X, PVX)
• Bees (eg. Pepino mosaic virus, PepMV)
• Nematodes (eg. Grapevine fan leaf virus, GFLV)
• Cuscuta species (eg. Cucumber mosaic virus, CMV)
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Photos: Szabolcs J.
Virus transmission by Oulema species (BMV)
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Colorado beetle as a vetor of potato virus
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Symptoms of rhyzomania and its vector (Polymyxa sp.)
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Cuscuta species as virus vectors
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Transmission by sucking and chewing insects
• Stylet borne non peristent transmission
• Peristant transmission
- Circulative (don’t replicate in the insect vector) - Propagative (replicates in the vector host)
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Characteristics of non - persistent virus transmission
• Viral coat protein attaches to the surface of stylet by the virus helper component
• After some „probe feeding” stops
• Starving enhance the transmission rates
• Sloughing off skin loose the transmissibility
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Characteristics of persistent transmission
• Virions get through the stylet into the intestines of the vector by the acquisition feeding
• Actively penetrate the posterior mid-gut wall
• Translocated passively by the haemolymph to the salivary glands
• From salivary glands get to the plant tissues by the infective feeding
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Practical points of vector transmission
• The non - persistent transmission means
immediately infection, incalculable, the chemical control is difficult, but takes for a short time
• The retention time in the case of persistent
transmission takes easy the chemical control, but the threat of infection is permanent
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Organization types of plant virus genomes
• Virus genes should represent all information for the replication
• There are no repetitive sequences among viruses
• Some functions are ruled by more genes
• Genome organization and replication process is characteristic both in animal and plant viruses
• New taxonomy of viruses based on the genome organization and replication
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Specific structures of virus RNAs
• Specific structures on the 5’- end:
- 7methyl guanosine cap or,
- VPg - protein liked to the genome
• Specific formation on the a 3’-end
- tRNA structure (recognition site of replicsase) or, - poly-A (adenine) tail
• Non coding regions
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„Indispensable viral genes”
• Replicase gene
• Helicase gene
• Coat protein gene(s)
• Meovement protein gene(s)
• Helper component gene
• Proteases
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Open reading frames (ORF)
• Start signal, gene, stop codon
• Read-trough proteins
• Overlapping genes: two protein will formed
• In the case of negative stranded viruses: a new mRNA is necessary
• In the case of DNA viruses: new mRNA is necessary (35S RNS)
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Main steps of virus replication
• a. Attachment to leaf cell and penetration
• b. Uncoating, bounding to ribosome's
• c. Early protein synthesis (polymerase)
• d. Transcription, replicative forms and intermediers
• e. RNA translation to protenis (late protein synthesis, MP, CP)
• f. Assembly (nucleic acids and coat protein)
• g. Accumulation (release or/and movement)
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Replication strategy: TMV
• In the cytoplasm. Role of replication factor
• Synthesis of two proteins in overlapping frames (ORF1 - 126 and ORF2 183 K) polymerases
• ORF3 (54 K) silent
• Subgenomic RNA-ses:
I2 RNS - ORF4 (30 K) MP and sRNS (LMC) - ORF5 (17.6 K) CP
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Replication strategy: CPMV
• Replication in the cytoplasm
• VPg on the RNS 5’end, poly A on the 3’end
• Divided genome (M and B)
• Replicase in the B component (110 K)
• M and B components replicate separately (two ORF)
• Post-translational cleavage of proteins (105 and 202 K) (B 32 K protease)
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Replication strategy: BMV
• Replication in the cytoplasm
• Divided genome: B (RNA1), M (RNA3 and sgRNA4), L (RNA2) and T component (empty)
• 7mG cap on the 5’ end, tRNA on the 3’end
• One ORF in each RNA except (RNA3)
• Efficient product of CP, pseudo recombinants
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Replication strategy: PVY
• In the cytoplasm, one long 9kb ORF
• Protein products:
- P1 serine protease
- HC-Pro helper component (aphid transmission) - P3-6K1 pathogenicity determinant
- CI cytoplasmic inclusion, helicase (movement) - 6K2 membrane bound, RNA replication
- NIa nuclear inclusion, precursor of VPg and 27K pro - VPg virion protein, infectivity
- 27K pro serine protease
- NIb nuclear inclusion, polymerase
- CP Coat protein (movement, aphid transmission)
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Replication strategy: CaMV
• dsDNA, minichromosome in the nucleus
• 35S RNA as a transcription product
• Reverse transcriptase produce a DNA copy
• Formation of DNA strands in the viroplasm
• ORFI. -37 K from the cell wall (MP), ORFII. and III. - 18 HC and 15 K structural, ORFIV. 57 K (pro-CP) 42 K,
ORFV. RT, ORFVI. viroplasma, ORFVII. and VIII.
unknown functions
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Replication strategy: TSWV
• Doubled external glycoprotein envelope
• L- RNA with negative, M and S ambisense polarity (+/-)
• Protein translation partly directly (+), partly by synthesis of mRNA (-)
• Replication in the viroplasm
• Synthesis of envelope in the endoplasmic reticulum
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Replication of satellite viruses and satellit RNAs-es
• Satellite viruses encapsidated in separated virions, while satellite RNAs have no virions, but
encapsidated in the virions of helper virus
• Replication made by the helper virus RNA
(polymerase), and satellite RNA does not encodes proteins
• satRNA inhibits the replication of helper RNA
• Modify (by strengthening or weakening) the symptoms
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Defective interfering (DI) RNA-ses
• The defective viruses are false products of helper virus replication, witch are not able to multiply without the helper virus
• Products of autocatalysis, or the false function of polymerases
• Interfers with virus multiplication and modifies the symptoms (DI)
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Most important strategies of gene expression!
• Production of one polyprotein (PVY)
• Read-trough proteins (TMV)
• Divided genomes (CPMV, BMV)
• Subgenomic RNA (TMV, BMV)
• Altered reading frames (TSWV)
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New taxonomy and evolution of viruses
• 5’ end and 3’ end of some virus RNS-ses are similar
• Similar arrangements of gene structures exist in some plant virus groups, similar to animal viruses
• Similar replication strategies
• New virus taxonomy based on replication strategies, reflecting the evolutionary similarities not on the
morphological properties
• Virus super families of animal and plant viruses:
- Sindbis virus super group - Picorna virus super group
- Retro (pararetro) virus super group
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Sindbis virus super group
• Tobacco mosaic virus (TMV)
• Alfalfa mosaic virus (AMV)
• Brome mosaic virus (BMV)
Genome organization and replicase strategies are the same, similar conserved sequences exist
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Picorna virus super family
• Cowpea mosaic virus (CPMV)
• Potato virus Y (PVY)
• Tomato black ring virus (TBRV)
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Pararetroviruses
• Cauliflower mosaic virus, CaMV
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Luteoviruses as transitional types
• Potato leafroll virus, PLRV,
• Barley stripe mosaic virus, BSMV
• Tomato bushy stunt virus, TBSV
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Evolution possibilities (theories)
• Monophyletic evolution
• Different ways of evolution (polyphyletic), but became similar in the course of coo-evolution
• Independent evolution with transduction of different genes
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Evolution mechanisms
• Gene erosion forces (chemical, physical)
• Mistakes in the translation and in the reparation mechanisms (RNS-DNS)
• Mistakes during the replication (DI)
• Gene (component) exchanges in the multicomponent viruses
• Hetero encapsidation
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Viroids
• Viroidos are subviral elements, a specific group of plant pathogens, similar to plant viruses
• Contained circular DNA in their genome, about 350 nt
• No coat protein shell
• Spread by wounds or by graftings
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Theodor O. Diener (1971) Viroids
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Main groups of viroids
• Pospiviroid (Potato spindle tuber viroid, PSTVd)
• Ansunviroid (Avocado sunblotch viroid, ASBVd)
• Pelamoviroid (Peach latent mosaic viroid, PLVVd)
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Main fields of virus control
• Genetic control: breeding for resistant (or tolerant) varieties, genetically modified organisms (GMO)
• Agro technical control:
- Disposition prophylaxis: plants in the best
physiological stage are more resistant to diseases - Infection prophylaxis: works by the inhibition of
infection processes
• Chemical: antiviral substances (direct effect) and chemicals enhancing the natural resistance
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Forms of plant breeding
• Resistance breeding by traditional methods (selection, crossing, selection)
• Resistance breeding by biotechnological methods:
- pathogen derived resistance (PDR) - use of natural plant resistance genes
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Challenges in biotechnology
• To know the mechanism of genes, and its expression products
• To establish the relationship of genes on the basis of nucleotide sequences
• To develop new diagnostic methods
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Construction of an infective transcript
• Extraction and purification of virus RNA
• Synthesis of complementary DNA (cDNA) by reverse transcriptase
• Amplification of cDNA by PCR
• Construction of infective forms by incorporation of promoters of a bacteriophages or viruses (T7, SP6, T3 or CaMV 35S RNA promoter
• Cap or VGp for infectivity
• Incorporation of cDNAs into bacterial plasmid
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Development of pathogen derived resistance
• Coat protein gene, or other genes (replicase, movement protein gene, proteases, etc.)
• Other nucleic acids, or fragments
• Satellite RNAs
• Non coding sequences
• Defective interfering nucleic acids (DI)
• Antisense forms
• Ribosymes
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Possible environmental threats of PDR
• The pathogenicity of the pathogen will change
• The susceptibility of plant change (to a new pathogen)
• Hetero- or trans encapsidation (vector specificity will change)
• Gene spread (by the pollen of GMO)
• Gene erosion (the number of cultivars will be reduced)
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Direct use of plant resistant genes
• Natural selection of resistance genes
• Protoplast fusions (eg. Solanum brevidens and S.
tuberosum)
• Search and incorporation of resistance genes (N, Tm, L) by GMO techniques
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Agrotechnical methods
• Healthy seeds
• Optimal plant nutrient supply
• Isolated seedling production
• Isolated production
• Forecasting of vectors
• Weed control
• Proper use of production lows
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Soil disinfection by steam
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Preparing the greenhouse for seed beds
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Preparation of plastic tunnels for production
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Tobacco seedling production by traditional way
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Modern seedling production in the greenhouse
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Hydroponic culture of tomato plants
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Tobacco cultrue or Ambrosia field?
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Yellow and blue sticky traps for thrips monitoring
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Sucking trap types for aphid monitoring
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Yellow water traps for aphid monitoring
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Cultivation of similar cultures in the neighborhood
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Isolated cultures inside the greenhouse
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Biological protection using attenuated virus strains
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Correct waist collection
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Incorrect way of waste collection
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Negligent of hygiene rules
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Incorrect way of production
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Correct form of production
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The keeping of hygiene rules results healthy plants
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Chemical control
• (Only if there is no other chance)
• Control of vector species and weeds
• Substances enhancing the natural resistance
• Antiviral substances
Plant Virology
Viruses and Virus diseases
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1. The most important single stranded RNA viruses
Rod shaped virions and their type representatives
Tobamovirus - Tobacco mosaic virus Tobravirus - Tobacco rattle virus
Hordeivirus - Barley stripe mosaic virus Furovirus - Soilborne wheat mosaic virus Pecluvirus - Peanut clump virus
Pomovirus - Potato mop top virus
Benyvirus - Beet necrotic yellow vein virus
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2. The most important single stranded RNA viruses
Filamentous virions and their type representatives
Carlavirus – Carnation latent virus
Capillovirus – Apple stem growing virus Potexvirus – Potato virus X
Allexivirus – Shallot virus X
Trichovirus – Apple chlorotic leafspot virus Foveavirus – Apple stem pitting virus
Vitivirus - Grapevine virus A Potyvirus - Potato virus Y
Closterovirus - Beet yellows virus
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3. The most important single stranded RNA viruses
Isometric viruses and their type representatives
Tombusvirus - Tomato bushy stunt virus Carmovirus - Carnation mottle virus
Dianthovirus - Carnation ring spot virus Luteovirus - Barley yellow dwarf virus Polerovirus - Potato leafroll virus
Enamovirus - Pea enation mosaic virus
Sobemovirus - Southern bean mosaic virus Tymovirus - Turnip yellow mosaic virus
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4. The most important single stranded viruses
Isometric virions with divided genome and their representatives
Comovirus - Cowpea mosaic virus Fabavirus - Broad bean wilt virus Nepovirus - Tobacco ring spot virus
Bromovirus - Brome mosaic virus
Cucumovirus - Cucumber mosaic virus Ilarvirus - Tobacco streak virus
Alfamovirus - Alfalfa mosaic virus
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5. The most important double stranded RNA viruses
• Reoviridae
Phytoreovirus - Wound tumor virus Fijivirus - Fiji disease virus
Oryzavirus - Rice ragged stunt virus
• Partitiviridae
• Alphacryptovirus - White clower crypto virus 1
• Betacryptovirus - White clower crypto virus 2
• Varicosavirus - Lettuce big-vein virus
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6. The most important negative stranded viruses
• Cytorhabdovirus - Lettuce necrosis wellows virus
• Nucleorhabdovirus - Potato yellow dwarf virus
• Tospovirus - Tomato spotted wilt virus
• Tenuivirus - Rice stripe virus
• Ophiovirus - Citrus psorosis virus
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7. The most important DNA viruses
• Double stranded (dsDNA) viruses and their representatives
Caulimovirus - Cauliflower mosaic virus
Badnavirus - Commelina yellow mottle virus
• Single stranded (ssDNA) viruses and their representatives
Curtovirus - Beet curle top virus Mastervirus - Maize streak virus
Begomovirus - Bean golden mosaic virus Nanovirus - Subterran clover stunt virus
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Tobacco mosaic virus (TMV)
• Tobacco mosaic virus group with about 12 related viruses
• 300 x 18 nm rigid, helical, rod shaped stable virions covered with 2130 protein subunits
• Genome with about 6400 nt, 86.4 kb. ssRNA
• Spreads by wounds and by mechanical way
• Mosaic pattern, chlorosis, leaf deformation
• Infects the tobacco, pepper, tomato
• Control: resistant varieties, keep the hygiene rules
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Tobamoviruses
Economically important tobamoviruses Tobacco mosaic virus
Tomato mosaic virus
Pepper green mottle virus Pepper mild mottle virus Obuda pepper virus
Odontoglossum ring spot virus
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Symptoms of TMV on tobacco
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Tobacco rattle virus (TRV)
• Two component, rigid rods with helical structure (190 and 80-110 nm x 22 nm)
• RNS1 – 6.8 kb., RNS2 – 1,8-4,5 kb.
• Spreads by nematodes (Trichodorus,
Paratrichodorus), mechanical way and by tubers
• Infects the tobacco (leaf and stem necrosis), potato (ring necrosis on the tubers)
• In the case of infection the potato production is not allowed for years!
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Barley stripe mosaic virus (BSMV)
• Helical, rigid virions with three components (100-150 x 20 nm)
• Causes chlorosis, stripes, mosaic, necroses, dwarfing and yield losses on Gramineous plants
• Spreads by mechanical way, by pollen and seeds!
• Control: healthy seeds
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Symptoms of Barley stripe mosaic virus infection
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Beet necrotic yellow vein virus
• Two rod shaped virions 260- 300 nm and 140-160 nm large and 18-24 nm in diameter
• Infects sugar beets and members of
Chenopodiaceae, causing the abnormal development of secondary roots (rhizomania)
• Vectored in soil by Polymyxa betae (Plasmodiophoraceae) fungus
• Control: healthy seed, resistant (tolerant) varieties
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Symptoms of rhizomania and its vector Polymyxa betae
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Potato virus X (PVX)
• Potato mild mosaic
• Single stranded, 470-580 nm long, 11-23 nm in diameter, filamentous virions
• RNA (5.8-7.0 kb) single component
• Cause mild mosaic on potato or symptom less
• Spreads by mechanical way, by tubers and by Leptinotarsa decemlineata beetles
• Control: use of healthy potato tubers
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Grapevine virus A (GVA)
• One component of grapevine decline process
• Linear, fliamentous virions about 800 nm long, 12 nm in diameter virions
• Infects the grapevines, spread by leaf miners, but other Vitiviruses by aphid
• Minor economic impact
• Control: healthy propagation material
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Potato virus Y (PVY)
• Type member of Poytviridae
• Economically important viruses, about 90 species
• Elongated 700-750 nm long flexuous virions
• The most important members:
- Potato virus Y (PVY)
- Maize dwarf mosaic virus (MDMV) - Sugarcane mosaic virus (SCMV) - Plum pox virus (PPV)
- Zucchini yellow mosaic virus (ZYMV) - Soybean mosaic virus (ZYMV)
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Potato virus Y
• Potato virus Y vírus – severe mosaic
• Flexuous, filamentous helical virions, cca. 11-15 nm x 650-900 nm
• Infects potato (dark spots, leaf necroses, tuber necrosis, apical necrosis)
• Spreads by aphids by non- persistent manner, and mechanically and vegetative (by tubers)
• Control: healthy seed potato, chemical control of aphids according to the aphid forecasting
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Necrotic symptoms caused by PVY
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PVY
NPVY necrotic strain causes veinal necrosis on tobacco
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PVY
NTNSymptoms of PVY tuber necrotic strain
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Leaf deformation and dwarfing caused by (PVY)
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Maize dwarf mosaic virus (MDMV)
• Elongated flexuous, 700-750 nm-large helical virions
• Infects the sorghum species and maize causing mosaic stripes
• Vectored by aphids by non-persistant manner, mechanically and by seeds (?)
• Over wintering host: Sorghum halepense
• Control: chemical control of aphids, use of resistant varieties
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MDMV infection on maize
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MDMV infection causes severe yield loss
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Symptoms of MDMV on sorghum and Johnson grass
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Sugarcane mosaic virus
• Infects first the sugarcane varieties, but it is known a strain infecting the maize too (MDMV-A)
• Long stripes along the veins, dwarfing, yield loss
• Elongated 750 x 11 nm flexuous virions
• Spreads by vegetative propagation (sugarcane) and by aphids by non-persistent manner
• Control: resistant or tolerant varieties
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Sugarcane mosaic virus infection on maize
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Plum pox virus (PPV)
• Sharka (plox) virus
• Long, flexuous helical virions (760 x 12 nm), one component RNA about 10 kb
• Infects plum, apricot and peach, greengage, causing mosaic symptoms, ring spots, sharka symptoms on stone fruits
• Spreads by vegetative propagation, mechanical
transmission, and by aphids (non-persistent manner)
• Control: No resistant variety is known, eradication of diseased plants, GMO species
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PPV
Symptoms of PPV on plum leaves
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PPV symptoms on plum and apricot leaves
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Zucchini yellow mosaic virus
• Long, flexuous virions about 750 x 12 nm large
• Infects the Cucurbitaceous species (pumpkin, squash, watermelon, cucumber etc.)
• Causes yellowing, severe mosaic, leaf and fruit deformation
• Spreads by aphids and by outhher seed transmission
• Control: chemical methods against aphids
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Symptoms of zucchini yellow mosaic virus on squash
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Symptoms of zucchini yellow mosaic virus
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Bean common mosaic virus
• Infects all bean species (but only beans)
• Long, flexuous virions 750 long and 12 nm wide
• Causes mosaic symptoms, leaf destortion, dwarfing
• Spreads by pollen and seeds!
• Control: by using healty seeds
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Seed transmission (BCMV)
Healthy Infected Photo: L. Beczner
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Comparison of symptoms of BCMV and BYMV
BCMV BYMV
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Bean yellow mosaic virus
•
• Infects all bean varieties, and other LeguminousBab sárga mozaik vírus
species (pea, white clower, Gladiolus, etc.)
• Long, helocal filamentous virions (750 x 12 nm)
• Causes yellowins, yellow mosaic, leaf deformations and dwarfings
• Seed-borne in many plants (exept beans). Spreads by aphids
• Control: healty seeds, control of aphids
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Grapevine leaf roll associated virus
• Group of similar viruses (I-IX)
• Closterovirus long, flexuous (2000 nm) virionok
• Nine, serologically distinct viruses Ampelovirus (GLRaV 1,3,5)
Closterovirus (GLRaV 2)
• Symptoms: leaf roll, redding, small berries
• Spreads by scale insects: Pseudococcus,
Planococcusspecies and by vegetative materials
• Control: healthy vegetative propagation materials
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Grapevine leaf roll symptoms on red grape varieties
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Grape leaf roll symptoms on white grape varieties
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Symptoms of Barey yellow dwarf virus infection
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Barley yellow dwarf virus (BYDV)
• Isometric, single component 25-30 nm virions, with about 6 kb large genome
• Infects the Gramineous plants (barley, wheat, rice, oat etc.)
• Causes yellowing, dwarfing, redding, inhibition of headings, sterility and great yield losses
• Spreads by aphids (persistent manner), the strains (or individual viruses) are distinguished according to the main vector species)
• Control: optimal time of showing, resistant varieties, chemical control of aphids
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Potato leaf roll virus (PLRV)
• Infects only the potato, but causes severe yield loss
• Isometric virions about 25-30 nm in diameter, single stranded RNS, about 6 kb
• The leaves are rolling, yellowing, anthocyane
accumulation, severe stunting, some varieties show phloem necrosis
• Spreads by infested tubers, but mechanically not
• Vectored by aphids by persistent manner
• Control: resistant varieties, chemical control of aphids based by vector forecasting, defoliation before harvesting
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PLRV
Symptoms of Potato leafroll virus
Healthy Diseased
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Leaf roll and accumulation of anthocyane (PLRV)
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A PPV fertőzés levéltünetei Fotó:Nagy Rébék Renáta
• Grapevine infectious decline (Grapevine fanleaf virus, GFLV)
• Arabis mosaic virus, ArMV)
• Grapevine chrome mosaic virus, GCMV)
• Tomato black ring virus, TBRV)
• (Grapevine Bulgarian latent virus, GBLV)
Nepoviruses responsibles for grapevine decline
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Grapevine fanleaf virus
• Grapevine fanleaf virus as a type of nepoviruses
• NEmatode transmitted POlyhedral (NEPO) viruses with similar properties, (30 nm). Two components RNS1 8-8,4 kb and RNS2 3,4 7,2 kb
• Similar viruses: Tomato ring spot virus, Cherry leaf roll virus, Arabis mosaic virus, Raspberry ring spot virus
• Vegetative transmission (grafting), Longidorus,
Paralongidorus és Xypinema species, by pollen and seeds
• Control: healthy grafting material, nematicides
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Symptoms of Grapevine fanleaf virus
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Symptoms of Grapevine chrome mosaic virus
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Cherry leaf roll virus
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Symptoms of CLRV on elder (Sambucus nigra)
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Apple mosaic virus
• Representative of Ilarviruses
• Labile, isometric, 25 and 29 nm large virions
• Symptoms: mosaic pattern, sometimes venial necroses, symptom less in summer
• Spreads by vegetative propagation (budding) and mechanically (with difficulties) (by seeds?)
• Control: heat treatment (37 Co, 27 days)
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Tipikus MDMV tünet a finom
mozaikfoltosság, levélcsíkozottság
Symptoms of Apple mosaic virus
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Symptoms of Apple mosaic virus
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Leaf deformation caused by PNRSV
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Enations caused by PNRSV infection
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Brome mosaic virus (BMV)
• Type member of Bromoviruses
• Infects Gramineous plants (wheat, barley, oat) and some Dicots (tobacco)
• Isometric virions of three components, 26 – 35 nm in diameter, three genomic and one subgenomic RNA
• Cause mosaic, stripes, dwarfing and sometimes necrosis
• Transmitted by mechanical means, by beetles (Oulema sp.)
• Control of Oulema species (both larvae and adults)
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BMV is vectored by Oulema species
Photos : Szabolcs J.
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Cucumber mosaic virus (CMV)
• Type member of Cucumoviruses
• One of the most distributed plant viruses, infecting more than 100 hosts (vegetables, ornamental plants)
• Symptoms: mosaic, leaf deformation, flower
distortion, stunting and dwarfing. Causes great yield losses
• Spreads by mechanical means, by aphids, in some cases with seeds
• Control: The resistance in the majority of cases are not solved. Use tolarant varieties, keep the rules of hygiene, control of aphids and weeds
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Symptoms of Cucumber mosaic virus infection
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Blossom and leaf deformation (CMV) on peppers
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„Oak leaf patterns” (CMV) on green pepper
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Leaf deformation and dwarfing caused by (PVY)
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Leaf deformation on tomato (CMV)
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Tomato spotted wilt virus (TSWV)
• Typical member of Tospoviruses
• Occurres mainly in tropical and subtropical areas, but cause severe yield losses in Hungary too
• Spherical virions with about 80-100 nm in diameter, covered by a glükoproteid envelope. Three genomic RNAs, the larges has negative polarity the two others are ambisense
• Its host range is very large, infects vegetables,
ornamental plants. In Hungary the tobacco, green pepper and tomato are affected
• Control: against Thrips tabaci and Frankliniella
occidentalis vectors. Its monitoring by yellow and blue sticky traps
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TSWV
Symptoms of Tomato spotted wilt virus on tomato
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TSWV symptoms on green pepper
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TSWV infection on tobacco field
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Cauliflower mosaic virus (CaMV)
• Type member of Caulimoviruses
• Isometric virions with 30 nm in diameter, the
genome has two DNA strands, containing about 8000 bases pairs
• Economic impact is low, but essential in the
biotechnological works as gene vector (GMO plants)
• Causes mild mosaic, vectored by aphids
• Control: against aphid vectors
• Use as gene vectors (GMO)
AZ ELŐADÁS LETÖLTHETŐ: -
Georgikon Kar
Növényvédelmi Intézet
Plant virology
Richard Gáborjányi DSc
