1Which of the following describes the most common shape of plant pathogenic bacteria?
A.Rod-shaped (Bacilli)
B.Spherical (Cocci)
C.Spiral (Spirilla)
D.Comma-shaped (Vibrio)
Correct Answer: Rod-shaped (Bacilli)
Explanation:The majority of plant pathogenic bacteria are rod-shaped (bacilli), whereas cocci and spirilla are less common in plant pathology.
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2Bacteria that have flagella distributed over the entire surface of the cell are termed:
A.Monotrichous
B.Lophotrichous
C.Amphitrichous
D.Peritrichous
Correct Answer: Peritrichous
Explanation:Peritrichous bacteria possess flagella distributed over the entire cell surface. Erwinia and Agrobacterium are examples.
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3Which component of the bacterial cell wall is primarily responsible for the structural difference between Gram-positive and Gram-negative bacteria?
A.Phospholipids
B.Peptidoglycan
C.Chitin
D.Cellulose
Correct Answer: Peptidoglycan
Explanation:Gram-positive bacteria have a thick layer of peptidoglycan, while Gram-negative bacteria have a thin layer of peptidoglycan covered by an outer membrane.
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4The primary method of reproduction in bacteria is:
A.Budding
B.Binary fission
C.Sporulation
D.Fragmentation
Correct Answer: Binary fission
Explanation:Bacteria primarily reproduce asexually through binary fission, where a single cell divides into two identical daughter cells.
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5Which standard reference is used for the classification of bacteria based on morphological, physiological, and metabolic characteristics?
A.Linnaeus' Systema Naturae
B.Bergey's Manual of Systematic Bacteriology
C.Ainsworth's Classification
D.ICTV Report
Correct Answer: Bergey's Manual of Systematic Bacteriology
Explanation:Bergey's Manual is the main resource for determining the identity of prokaryotic organisms, emphasizing bacterial classification.
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6What is the primary distinguishing feature of Mollicutes (Phytoplasmas and Spiroplasmas) compared to true bacteria?
A.Lack of a nucleus
B.Lack of a cell wall
C.Presence of chlorophyll
D.Inability to replicate
Correct Answer: Lack of a cell wall
Explanation:Mollicutes are distinguished by the absence of a rigid cell wall, being bounded only by a unit membrane.
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7Which antibiotic are Mollicutes generally sensitive to?
A.Penicillin
B.Tetracycline
C.Streptomycin
D.Ampicillin
Correct Answer: Tetracycline
Explanation:Since Mollicutes lack a cell wall, they are resistant to penicillin (which inhibits cell wall synthesis) but are sensitive to tetracycline, which inhibits protein synthesis.
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8On solid media, colonies of many Mollicutes exhibit a characteristic appearance described as:
A.Cottony growth
B.Slimy exudate
C.Fried egg appearance
D.Irregular mosaic
Correct Answer: Fried egg appearance
Explanation:Mollicutes, particularly Mycoplasma and Spiroplasma, often form colonies that look like a fried egg, with a denser center and lighter periphery.
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9Which of the following is a Fastidious Vascular Bacterium limited to the xylem vessels?
A.Xylella fastidiosa
B.Candidatus Liberibacter
C.Pseudomonas syringae
D.Xanthomonas campestris
Correct Answer: Xylella fastidiosa
Explanation:Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes diseases like Pierce's disease of grapes.
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10Candidatus Liberibacter species are generally restricted to which plant tissue?
A.Xylem
B.Phloem
C.Epidermis
D.Parenchyma
Correct Answer: Phloem
Explanation:Candidatus Liberibacter, the cause of Citrus Greening (Huanglongbing), is a fastidious bacterium restricted to the phloem sieve tubes.
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11A fully assembled infectious virus particle is called a:
A.Capsid
B.Viroid
C.Virion
D.Prion
Correct Answer: Virion
Explanation:A virion is the complete, infectious virus particle, consisting of the nucleic acid genome and the protein coat (capsid).
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12The protein coat surrounding the nucleic acid of a virus is known as the:
A.Capsule
B.Capsid
C.Envelope
D.Peplomer
Correct Answer: Capsid
Explanation:The capsid is the protective protein shell made up of subunits called capsomeres that encloses the viral genome.
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13Most plant viruses contain which type of genetic material?
A.dsDNA
B.ssDNA
C.ssRNA
D.dsRNA
Correct Answer: ssRNA
Explanation:The majority of plant viruses possess single-stranded RNA (ssRNA), usually positive-sense.
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14Tobacco Mosaic Virus (TMV) has a morphology best described as:
A.Isometric (Polyhedral)
B.Rigid rod
C.Flexuous thread
D.Bacilliform
Correct Answer: Rigid rod
Explanation:TMV particles are rigid, rod-shaped structures approximately nm.
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15In the context of viral replication, what happens during 'uncoating'?
A.The virus attaches to the cell wall
B.The protein coat is removed to release the nucleic acid
C.New viral proteins are synthesized
D.The virus exits the cell
Correct Answer: The protein coat is removed to release the nucleic acid
Explanation:Uncoating is the process where the viral capsid is removed or degraded, releasing the viral genome into the host cell for replication.
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16Which mode of virus transmission involves the virus being retained in the vector for a long period, often for life, and potentially replicating within the vector?
Explanation:In persistent transmission, the vector retains the virus for a long time (often life), and in propagative types, the virus replicates inside the vector.
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17Cuscuta spp. (Dodder) is classified as a:
A.Total root parasite
B.Partial root parasite
C.Total stem parasite
D.Partial stem parasite
Correct Answer: Total stem parasite
Explanation:Cuscuta is a holoparasite (total parasite) that attacks the stems of host plants, lacking chlorophyll and true roots.
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18The specialized absorbing organ used by phanerogamic parasites to draw nutrients from the host is called:
A.Rhizoid
B.Appressorium
C.Haustorium
D.Sclerotium
Correct Answer: Haustorium
Explanation:Haustoria are specialized structures that penetrate the host tissue (xylem/phloem) to absorb water and nutrients.
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19Striga species are commonly known as:
A.Dodder
B.Witchweed
C.Broomrape
D.Mistletoe
Correct Answer: Witchweed
Explanation:Striga is commonly referred to as Witchweed and is a major parasite of cereal crops like sorghum and maize.
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20Orobanche spp. (Broomrape) is a parasite primarily of which plant part?
A.Stem
B.Root
C.Leaf
D.Flower
Correct Answer: Root
Explanation:Orobanche is a total root parasite that attaches to the roots of hosts, commonly affecting Solanaceous crops.
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21Which of the following is a semi-stem parasite?
A.Cuscuta
B.Orobanche
C.Loranthus (Dendrophthoe)
D.Striga
Correct Answer: Loranthus (Dendrophthoe)
Explanation:Loranthus (and Viscum) are semi-stem parasites (hemiparasites); they have chlorophyll but rely on the host for water and minerals.
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22The algal parasite Cephaleuros virescens causes which disease?
A.Red rust of tea/mango
B.Downy mildew
C.Powdery mildew
D.Club root
Correct Answer: Red rust of tea/mango
Explanation:Cephaleuros virescens is a parasitic green alga that causes Red Rust disease in tea, mango, and other fruit trees.
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23Bacterial genes responsible for pathogenicity are often located on:
A.Ribosomes
B.Plasmids
C.Mesosomes
D.Capsules
Correct Answer: Plasmids
Explanation:Plasmids are extrachromosomal DNA elements that often carry virulence genes (e.g., the Ti plasmid in Agrobacterium).
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24What is the typical size range of plant pathogenic bacteria?
A.0.5 - 3.0
B.10 - 100
C.20 - 300 nm
D.1 - 2 cm
Correct Answer: 0.5 - 3.0
Explanation:Bacteria are microscopic prokaryotes, typically ranging from 0.5 to 3.0 micrometers in length.
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25Phytoplasmas are primarily transmitted by which group of insects?
A.Aphids
B.Leafhoppers/Planthoppers
C.Whiteflies
D.Thrips
Correct Answer: Leafhoppers/Planthoppers
Explanation:Phytoplasmas are phloem-limited and are transmitted in a persistent manner mainly by leafhoppers and planthoppers.
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26Which term describes the helical, motile nature of Spiroplasma?
A.Pleomorphic
B.Spiral/Helical
C.Icosahedral
D.Amorphous
Correct Answer: Spiral/Helical
Explanation:Spiroplasma gets its name from its spiral (helical) morphology and its ability to move (motility), distinguishing it from Phytoplasmas.
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27Viral inclusion bodies are:
A.Bacterial contaminants
B.Aggregates of virus particles or viral products inside the cell
C.Plant defense structures
D.Dead host cells
Correct Answer: Aggregates of virus particles or viral products inside the cell
Explanation:Inclusion bodies are intracellular structures formed by the aggregation of viral proteins or particles, often diagnostic for specific viral infections.
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28The movement of plant viruses from cell to cell occurs through:
A.Stomata
B.Plasmodesmata
C.Xylem vessels
D.Cuticle
Correct Answer: Plasmodesmata
Explanation:Viruses move between adjacent plant cells via plasmodesmata, often aided by specific viral movement proteins.
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29Long-distance transport of viruses within the plant usually occurs via the:
A.Xylem
B.Phloem
C.Pith
D.Cortex
Correct Answer: Phloem
Explanation:Systemic infection involves the rapid movement of the virus through the phloem sieve elements along with photosynthates.
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30Which of the following describes a 'multipartite' virus?
A.A virus with multiple protein coats
B.A virus whose genome is divided into separate nucleic acid segments packaged in different particles
C.A virus that attacks multiple hosts
D.A virus with DNA and RNA
Correct Answer: A virus whose genome is divided into separate nucleic acid segments packaged in different particles
Explanation:Multipartite viruses have segmented genomes where the segments are encapsidated in separate particles; all parts are often needed for infection.
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31The transmission of viruses by aphids where the virus is carried on the stylet and lost after molting is called:
A.Non-persistent (Stylet-borne)
B.Circulative
C.Propagative
D.Transovarial
Correct Answer: Non-persistent (Stylet-borne)
Explanation:In non-persistent transmission, the virus is acquired quickly and held on the stylet tips, but infectivity is lost rapidly and the virus is not retained after molting.
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32Striga is a partial (semi) root parasite. This means:
A.It has no chlorophyll and relies totally on the host
B.It has chlorophyll but relies on the host for water and minerals
C.It lives entirely inside the root
D.It does not produce seeds
Correct Answer: It has chlorophyll but relies on the host for water and minerals
Explanation:Semi-parasites (hemiparasites) like Striga perform photosynthesis but depend on the host root system for water and nutrients.
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33The slime layer or capsule of bacteria is chemically composed mainly of:
A.Polysaccharides
B.Lipids
C.Nucleic acids
D.Inorganic salts
Correct Answer: Polysaccharides
Explanation:The extracellular slime layer or capsule is primarily composed of extracellular polysaccharides (EPS), which aid in protection and virulence.
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34Which bacterial structure is involved in the transfer of genetic material during conjugation?
A.Flagella
B.Pili (Fimbriae)
C.Mesosome
D.Ribosome
Correct Answer: Pili (Fimbriae)
Explanation:Sex pili are specialized appendages that facilitate the transfer of DNA (plasmids) between bacteria during conjugation.
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35Which of the following is NOT a method of plant virus transmission?
A.Vegetative propagation
B.Insects vectors
C.Wind dissemination of virions
D.Seed transmission
Correct Answer: Wind dissemination of virions
Explanation:Plant viruses cannot penetrate the intact plant cuticle on their own; they require wounding or vectors. Wind alone does not transmit virions unlike fungal spores.
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36Common symptoms of Orobanche infection in tobacco or brinjal include:
A.Leaf mosaic
B.Stunting and yellowing of the host due to nutrient depletion
C.Stem galls
D.Fruit rot
Correct Answer: Stunting and yellowing of the host due to nutrient depletion
Explanation:Being a root parasite, Orobanche extracts nutrients, causing severe stunting, chlorosis, and yield reduction in the host.
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37The term 'bacteriophage' refers to:
A.A bacterium that eats plants
B.A virus that infects bacteria
C.A fungal parasite of bacteria
D.A bacterial toxin
Correct Answer: A virus that infects bacteria
Explanation:Bacteriophages are viruses that specifically infect and replicate within bacterial cells.
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38What is the function of the enzyme 'Reverse Transcriptase' in some viruses (e.g., Caulimoviruses)?
A.Synthesizes RNA from DNA
B.Synthesizes DNA from an RNA template
C.Degrades host DNA
D.Repairs viral capsid
Correct Answer: Synthesizes DNA from an RNA template
Explanation:Reverse transcriptase is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process used by retroviruses and pararetroviruses (like Caulimovirus).
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39Gram staining differentiates bacteria based on the ability to retain which dye complex?
A.Crystal violet-Iodine
B.Safranin-Malachite green
C.Methylene blue
D.Carbol fuchsin
Correct Answer: Crystal violet-Iodine
Explanation:Gram-positive bacteria retain the Crystal violet-Iodine complex (appearing purple), while Gram-negative bacteria lose it and take up the counterstain (appearing pink/red).
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40Which genus of bacteria is known for causing Crown Gall disease by transferring DNA into the plant genome?
A.Pseudomonas
B.Agrobacterium
C.Erwinia
D.Ralstonia
Correct Answer: Agrobacterium
Explanation:Agrobacterium tumefaciens (now Rhizobium radiobacter) transfers a segment of its Ti plasmid (T-DNA) into the plant host, causing tumors.
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41Which of the following plant pathogens is eukaryotic?
A.Xanthomonas
B.Phytoplasma
C.Green Algae (Cephaleuros)
D.Tobacco Mosaic Virus
Correct Answer: Green Algae (Cephaleuros)
Explanation:Algae are eukaryotes (possess a nucleus). Bacteria and Phytoplasmas are prokaryotes, and Viruses are acellular.
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42In viral taxonomy, family names end with the suffix:
A.-virus
B.-viridae
C.-ales
D.-mycota
Correct Answer: -viridae
Explanation:According to the ICTV, viral family names end in -viridae (e.g., Potyviridae).
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43What is the approximate sedimentation coefficient of bacterial ribosomes?
A.80S
B.70S
C.60S
D.40S
Correct Answer: 70S
Explanation:Prokaryotic bacteria have 70S ribosomes (composed of 50S and 30S subunits), unlike the 80S ribosomes found in eukaryotic cytoplasm.
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44Transmission of viruses through vegetative parts like tubers, bulbs, or cuttings is known as:
A.Mechanical transmission
B.Vegetative transmission
C.Biological transmission
D.Transovarial transmission
Correct Answer: Vegetative transmission
Explanation:Vegetative transmission occurs when infected plant parts (tubers, cuttings, grafting material) are used for propagation, perpetuating the disease.
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45The phenomenon where a mild strain of a virus protects a plant against a severe strain of the same virus is called:
A.Synergism
B.Cross-protection
C.Hypersensitivity
D.Interference
Correct Answer: Cross-protection
Explanation:Cross-protection is a phenomenon where infection with a mild viral strain prevents subsequent infection or symptom development by a severe strain of the same virus.
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46Which phanerogamic parasite seeds require a chemical stimulant (strigolactones) from the host root exudates to germinate?
A.Cuscuta
B.Striga
C.Loranthus
D.Viscum
Correct Answer: Striga
Explanation:Striga seeds are dormant in the soil and require specific chemical stimulants (strigolactones) exuded by host roots to trigger germination.
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47Fastidious bacteria are difficult to study primarily because:
A.They are too small to see
B.They cannot be cultured on standard nutrient media
C.They have no DNA
D.They move too fast
Correct Answer: They cannot be cultured on standard nutrient media
Explanation:Fastidious bacteria have complex nutritional requirements and often cannot be grown on standard agar plates, requiring specialized media or host tissue.
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48The enzyme commonly produced by soft-rot bacteria (e.g., Pectobacterium) to degrade the middle lamella is:
A.Cellulase
B.Pectinase
C.Ligninase
D.Amylase
Correct Answer: Pectinase
Explanation:Soft rot bacteria produce pectinases that break down pectin in the middle lamella, causing tissue maceration and the characteristic 'soft rot'.
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49Nematodes can transmit plant viruses. Which shape of nematode is typically associated with virus transmission?
A.Cyst nematodes
B.Root-knot nematodes
C.Dagger and Needle nematodes (Ectoparasitic)
D.Seed gall nematodes
Correct Answer: Dagger and Needle nematodes (Ectoparasitic)
Explanation:Viruses (like Nepoviruses and Tobraviruses) are transmitted by ectoparasitic nematodes such as Xiphinema (Dagger) and Longidorus (Needle).
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50Which of the following best describes the shape of Gemini virus particles?
A.Rod shaped
B.Twin icosahedra (Geminate)
C.Filamentous
D.Bullet shaped
Correct Answer: Twin icosahedra (Geminate)
Explanation:Geminiviruses have a unique morphology consisting of two fused incomplete icosahedrons, resembling twins (hence 'Gemini').