MCQs on Plant Pathogenic Organisms

1. Which type of organism causes Citrus canker?
   1. A. Fungi
   2. B. True bacteria
   3. C. Protozoa
   4. D. Virus
      Answer: B
2. Citrus greening and Pierce’s disease of grapes are caused by which group of pathogens?
   1. A. True bacteria
   2. B. Rickettsia-like bacteria
   3. C. Mycoplasma-like organisms
   4. D. Viruses
      Answer: B
3. Which pathogen causes Sesame phyllody and eggplant little leaf?
   1. A. Spiroplasma
   2. B. Mycoplasma-like organism (MLO)
   3. C. Algae
   4. D. Viroids
      Answer: B
4. What is an example of a disease caused by Spiroplasma?
   1. A. Corn stunt
   2. B. Wilt of cotton
   3. C. Red rust of mango
   4. D. Yellow mosaic of blackgram
      Answer: A
5. Which type of organism is the disease “heart rot of coconut” caused?
   1. A. Algae
   2. B. Protozoa
   3. C. Fungi
   4. D. Virus
      Answer: B
6. Which disease is caused by parasitic algae?
   1. A. Broomrape of tobacco
   2. B. Red rust of mango
   3. C. Root knot nematode
   4. D. Spindle tuber of potato
      Answer: B
7. Which parasitic flowering plant causes broomrape of tobacco?
   1. A. Protozoa
   2. B. Phanerogamic parasite
   3. C. Algae
   4. D. Fungi
      Answer: B
8. Root knot nematode is an example of which type of pathogen?
   1. A. Biotic agent
   2. B. Abiotic agent
   3. C. Mesobiotic agent
   4. D. Parasitic flowering plant
      Answer: A
9. Viruses and viroids are classified under which category of agents?
   1. A. Biotic agents
   2. B. Mesobiotic agents
   3. C. Abiotic agents
   4. D. Eukaryotic agents
      Answer: B
10. Which disease is caused by viroids?
    1. A. Citrus canker
    2. B. Spindle tuber of potato
    3. C. Yellow mosaic of blackgram
    4. D. Corn stunt
       Answer: B
11. What are the abiotic agents responsible for plant diseases?
    1. A. Mesobiotic agents
    2. B. Fungi and bacteria
    3. C. Environmental factors
    4. D. Viruses and viroids
       Answer: C
12. Which of the following is an example of a disease caused by improper soil moisture?
    1. A. Heart rot of coconut
    2. B. Damping off of seedlings
    3. C. Wilt of cotton
    4. D. Red rust of mango
       Answer: B
13. The primary structural component of fungal cell walls is:
    1. A. Cellulose or chitin
    2. B. Peptidoglycan
    3. C. Lipids
    4. D. Protein
       Answer: A
14. Who first reported the bacterial origin of plant disease?
    1. A. Adolf Mayer
    2. B. T. J. Burrill
    3. C. M. W. Beijerinck
    4. D. Robert Koch
       Answer: B
15. The first plant disease identified as being caused by a bacterium was:
    1. A. Fire blight of apple and pear
    2. B. Citrus canker
    3. C. Red rust of mango
    4. D. Wilt of cotton
       Answer: A
16. Fungi reproduce through:
    1. A. Simple fission
    2. B. Sexual and asexual spores
    3. C. Binary fission
    4. D. Plasmid transfer
       Answer: B
17. Which organism is eukaryotic and achlorophyllous with filamentous somatic structures?
    1. A. Bacteria
    2. B. Fungi
    3. C. Protozoa
    4. D. Viruses
       Answer: B
18. The primitive nucleus of bacteria is characterized by:
    1. A. A defined nuclear membrane
    2. B. Lack of a nuclear membrane
    3. C. Presence of nucleolus
    4. D. Multinucleate cells
       Answer: B
19. What is the approximate size of bacteria?
    1. A. 0.5 to 1.0 μm x 2.0 to 5.0 μm
    2. B. 5.0 to 10.0 μm x 10.0 to 20.0 μm
    3. C. 0.1 to 0.2 μm x 0.5 to 1.0 μm
    4. D. 1.0 to 2.0 μm x 5.0 to 10.0 μm
       Answer: A
20. The term “chlorophyll-free unicellular organisms multiplying by simple fission” refers to:
    1. A. Fungi
    2. B. Viruses
    3. C. Bacteria
    4. D. Protozoa
       Answer: C
21. 21. What are fastidious vascular bacteria also known as?
    • A. Phytoplasmas
    • B. Rickettsia-like bacteria (RLB)
    • C. Protozoa
    • D. Spiroplasma
      Answer: B
    22. Fastidious vascular bacteria reproduce through:
    • A. Budding
    • B. Binary fission
    • C. Spore formation
    • D. Vegetative propagation
      Answer: B
    23. RLB are restricted primarily to which plant tissues?
    • A. Xylem and phloem
    • B. Leaf mesophyll
    • C. Cortex and epidermis
    • D. Root cortex
      Answer: A
    24. Which of the following is NOT a transmission method for RLB?
    • A. Leafhoppers
    • B. Nematodes
    • C. Mechanical inoculation
    • D. Airborne spores
      Answer: D
    25. The RLB causing phony disease of peach is named:
    • A. Xylella fastidiosa
    • B. Erwinia amylovora
    • C. Agrobacterium tumefaciens
    • D. Pseudomonas syringae
      Answer: A
    26. Which disease is associated with xylem-limited RLB?
    • A. Citrus greening
    • B. Pierce’s disease of grapevine
    • C. Clover club leaf
    • D. Phyllody of sesame
      Answer: B
    27. The primary insect vector for Pierce’s disease of grapevine belongs to which family?
    • A. Cicadellidae
    • B. Aphididae
    • C. Psyllidae
    • D. Thripidae
      Answer: A
    28. What is a characteristic symptom of xylem-limited RLB infections?
    • A. Marginal necrosis of leaves
    • B. Witches’ broom
    • C. Virescence of flowers
    • D. Leaf mosaic
      Answer: A
    29. Which drug is effective against RLB?
    • A. Penicillin
    • B. Tetracycline
    • C. Sulfa drugs
    • D. Both A and C
      Answer: D
    30. Phloem-limited RLB were first recognized in which year?
    • A. 1960
    • B. 1970
    • C. 1980
    • D. 1990
      Answer: B
    31. Citrus greening is primarily transmitted by which insect?
    • A. Psyllina sp.
    • B. Cicadellidae
    • C. Aphididae
    • D. Thripidae
      Answer: A
    32. What is the primary difference between RLB and phytoplasmas?
    • A. Phytoplasmas have a cell wall; RLB do not.
    • B. RLB have a cell wall; phytoplasmas do not.
    • C. RLB are restricted to xylem; phytoplasmas are not.
    • D. RLB are larger than phytoplasmas.
      Answer: B
    33. Phytoplasmas are sensitive to which drug?
    • A. Penicillin
    • B. Tetracycline
    • C. Erythromycin
    • D. Sulfa drugs
      Answer: B
    34. Spiroplasma is an example of a:
    • A. Wall-less helical prokaryote
    • B. Phanerogamic parasite
    • C. Non-tissue restricted RLB
    • D. Abiotic pathogen
      Answer: A
    35. Which disease is caused by spiroplasma?
    • A. Corn stunt
    • B. Clover rugose leaf curl
    • C. Potato spindle tuber
    • D. Marchitez suppressive
      Answer: A
    36. Viruses differ from bacteria as they:
    • A. Lack enzymes for metabolism
    • B. Possess both DNA and RNA
    • C. Can multiply on artificial media
    • D. Are unaffected by environmental factors
      Answer: A
    37. Viroids are different from viruses because they:
    • A. Lack nucleic acids
    • B. Contain only RNA
    • C. Have a protein coat
    • D. Infect only fungi
      Answer: B
    38. The study of algae is called:
    • A. Mycology
    • B. Phycology
    • C. Algology
    • D. Both B and C
      Answer: D
    39. Which of the following diseases is caused by protozoa?
    • A. Red rust of mango
    • B. Heart rot of coconut
    • C. Little leaf of brinjal
    • D. Phyllody of sesame
      Answer: B
    40. What type of parasite is a phanerogamic parasite?
    • A. Algal
    • B. Fungal
    • C. Flowering plant
    • D. Bacterial
      Answer: C

41. Diseases limited to a specific area of a plant organ are classified as:

a) Systemic diseases
b) Localized diseases
c) Air-borne diseases
d) Sporadic diseases
Answer: b) Localized diseases

42. Which of the following is an example of a systemic disease?

a) Leaf spots caused by fungi
b) Anthracnoses
c) Mosaics and leaf curls caused by viruses
d) Early leaf spot of groundnut
Answer: c) Mosaics and leaf curls caused by viruses

43. Damping-off caused by Pythium species is an example of:

a) Air-borne disease
b) Seed-borne disease
c) Soil-borne disease
d) Systemic disease
Answer: c) Soil-borne disease

44. Which of the following is an internally seed-borne disease?

a) Blast of rice
b) Loose smut of wheat
c) Citrus canker
d) Late blight of potato
Answer: b) Loose smut of wheat

45. A disease consistently occurring year after year in a particular region is known as:

a) Sporadic disease
b) Pandemic disease
c) Epidemic disease
d) Endemic disease
Answer: d) Endemic disease

46. An example of an endemic disease in Asia is:

a) Wheat stem rust
b) Powdery mildew
c) Citrus canker
d) Late blight of potato
Answer: c) Citrus canker

47. A sudden outbreak of disease over a wide area in severe form is called:

a) Sporadic disease
b) Endemic disease
c) Pandemic disease
d) Epidemic disease
Answer: d) Epidemic disease

48. Which of the following is a sporadic disease?

a) Fusarium wilt of cotton
b) Rice blast
c) Sugarcane red rot
d) Downy mildew of grapevine
Answer: a) Fusarium wilt of cotton

49. Late blight of potato, which spreads across countries and continents, is an example of:

a) Sporadic disease
b) Endemic disease
c) Pandemic disease
d) Systemic disease
Answer: c) Pandemic disease

50. A disease that spreads slowly without repetition of the cycle within the crop season is termed as:

a) Simple interest disease
b) Compound interest disease
c) Sporadic disease
d) Endemic disease
Answer: a) Simple interest disease

51. Which of the following is an example of a compound interest disease?

a) Rhizoctonia root rot
b) Wheat stem rust
c) Fusarium wilt of cotton
d) Damping-off
Answer: b) Wheat stem rust

52. Which disease-causing agent is spread through air?

a) Blast of rice
b) Early leaf spot of groundnut
c) Damping-off
d) Loose smut of wheat
Answer: b) Early leaf spot of groundnut

53. A soil-inhabiting pathogen involved in simple interest disease is:

a) Puccinia graminis
b) Sclerotium sp.
c) Erysiphe graminis
d) Pyricularia oryzae
Answer: b) Sclerotium sp.

54. Diseases that involve rapid multiplication of inoculum during the crop season are:

a) Sporadic diseases
b) Endemic diseases
c) Compound interest diseases
d) Simple interest diseases
Answer: c) Compound interest diseases

55. Which of the following is NOT a characteristic of a systemic disease?

a) Limited to a definite area
b) Affects most host tissues
c) Can be caused by viruses
d) May involve downy mildews
Answer: a) Limited to a definite area

56. Which of the following is an air-borne disease of groundnut?

a) Anthracnose
b) Early leaf spot
c) Damping-off
d) Wart disease of potato
Answer: b) Early leaf spot

57. Wart disease of potato is endemic in:

a) Asia
b) Africa
c) Darjeeling
d) Europe
Answer: c) Darjeeling

58. Which of the following diseases spreads through seed material?

a) Blast of rice
b) Wheat stem rust
c) Early leaf spot
d) Citrus canker
Answer: a) Blast of rice

59. An example of a monocyclic epidemic is:

a) Rice blast
b) Powdery mildew
c) Damping-off caused by Pythium
d) Wheat stem rust
Answer: c) Damping-off caused by Pythium

60. Which pathogen causes a polycyclic epidemic with rapid spread during the crop season?

a) Rhizoctonia sp.
b) Puccinia graminis
c) Pythium sp.
d) Sclerotium sp.
Answer: b) Puccinia graminis