1. The study of plant diseases is called:
A) Mycology
B) Pathology
C) Phytopathology
D) Agronomy
Answer: C) Phytopathology
Explanation: Phytopathology is the branch of biology dealing with plant diseases, their causes, and control.
2. The Irish famine (1845) was caused by:
A) Wheat rust
B) Potato late blight
C) Rice blast
D) Citrus canker
Answer: B) Potato late blight
Explanation: Caused by Phytophthora infestans, leading to starvation in Ireland.
3. Crown gall disease in plants is caused by:
A) Fungus
B) Bacterium
C) Virus
D) Mycoplasma
Answer: B) Bacterium
Explanation: Agrobacterium tumefaciens causes crown gall by transferring Ti plasmid DNA into host plants.
4. Citrus canker is caused by:
A) Xanthomonas citri
B) Fusarium oxysporum
C) Tobacco mosaic virus
D) Pythium debaryanum
Answer: A) Xanthomonas citri
Explanation: Bacterial disease causing leaf and fruit lesions in citrus crops.
5. Black rot of crucifers is caused by:
A) Xanthomonas campestris pv. campestris
B) Alternaria brassicae
C) Fusarium oxysporum
D) Cercospora brassicicola
Answer: A) Xanthomonas campestris pv. campestris
Explanation: Produces V-shaped lesions in cabbage, cauliflower, mustard, etc.
6. Wilt disease of solanaceous crops (tomato, potato, brinjal) is caused by:
A) Ralstonia solanacearum
B) Agrobacterium tumefaciens
C) Xanthomonas oryzae
D) Erwinia carotovora
Answer: A) Ralstonia solanacearum
Explanation: Soil-borne bacterium causing bacterial wilt in solanaceous crops.
7. Fire blight of apple and pear is caused by:
A) Erwinia amylovora
B) Pseudomonas fluorescens
C) Xanthomonas citri
D) Agrobacterium tumefaciens
Answer: A) Erwinia amylovora
Explanation: First bacterial plant disease discovered (in 1878).
8. Soft rot of vegetables is caused by:
A) Erwinia carotovora
B) Xanthomonas campestris
C) Fusarium oxysporum
D) Phytophthora infestans
Answer: A) Erwinia carotovora
Explanation: Erwinia secretes pectolytic enzymes that soften tissues and cause rotting.
9. Red stripe disease of sugarcane is caused by:
A) Xanthomonas albilineans
B) Xanthomonas rubrilineans
C) Ralstonia solanacearum
D) Pseudomonas syringae
Answer: B) Xanthomonas rubrilineans
Explanation: Produces reddish streaks in sugarcane leaves.
10. Angular leaf spot of cotton is caused by:
A) Xanthomonas malvacearum
B) Fusarium oxysporum
C) Alternaria tenuis
D) Cercospora gossypina
Answer: A) Xanthomonas malvacearum
Explanation: Produces angular-shaped bacterial leaf spots in cotton.
11. Bacterial leaf blight of rice is caused by:
A) Xanthomonas oryzae pv. oryzae
B) Fusarium moniliforme
C) Pyricularia oryzae
D) Phytophthora infestans
Answer: A) Xanthomonas oryzae pv. oryzae
Explanation: Major bacterial disease of rice causing wilting and yellowing.
12. Bacterial leaf streak of rice is caused by:
A) Xanthomonas oryzae pv. oryzicola
B) Fusarium oxysporum
C) Phytophthora parasitica
D) Cercospora oryzae
Answer: A) Xanthomonas oryzae pv. oryzicola
Explanation: Produces yellowish streaks on rice leaves.
13. Bacterial wilt of cucurbits is caused by:
A) Erwinia tracheiphila
B) Xanthomonas campestris
C) Ralstonia solanacearum
D) Agrobacterium tumefaciens
Answer: A) Erwinia tracheiphila
Explanation: Spread by cucumber beetles, causes wilt in cucurbit plants.
14. Gumming disease of sugarcane is caused by:
A) Xanthomonas axonopodis
B) Leifsonia xyli
C) Ralstonia solanacearum
D) Erwinia carotovora
Answer: A) Xanthomonas axonopodis
Explanation: Produces gum-like exudates in sugarcane.
15. Bacterial stripe of maize is caused by:
A) Pseudomonas avenae
B) Xanthomonas campestris
C) Erwinia carotovora
D) Fusarium sp.
Answer: A) Pseudomonas avenae
Explanation: Produces long stripes in maize leaves.
16. Halo blight of beans is caused by:
A) Pseudomonas syringae pv. phaseolicola
B) Xanthomonas campestris
C) Fusarium oxysporum
D) Cercospora personata
Answer: A) Pseudomonas syringae pv. phaseolicola
Explanation: Produces water-soaked lesions with yellow halos.
17. Wildfire disease of tobacco is caused by:
A) Pseudomonas tabaci
B) Erwinia carotovora
C) Fusarium tabacum
D) Phytophthora tabacina
Answer: A) Pseudomonas tabaci
Explanation: Bacterial disease producing wildfire-like leaf spots.
18. Bacterial canker of tomato is caused by:
A) Clavibacter michiganensis
B) Xanthomonas campestris
C) Erwinia carotovora
D) Ralstonia solanacearum
Answer: A) Clavibacter michiganensis
Explanation: A gram-positive bacterium causing wilting and cankers in tomato.
19. Stewart’s wilt of maize is caused by:
A) Erwinia stewartii
B) Xanthomonas oryzae
C) Fusarium oxysporum
D) Ustilago maydis
Answer: A) Erwinia stewartii
Explanation: Produces wilting and streaks in maize leaves.
20. Olive knot disease is caused by:
A) Pseudomonas savastanoi
B) Agrobacterium tumefaciens
C) Xanthomonas campestris
D) Erwinia amylovora
Answer: A) Pseudomonas savastanoi
Explanation: Produces knot-like swellings on olive trees.
21. Bacterial scab of potato is caused by:
A) Streptomyces scabies
B) Xanthomonas citri
C) Erwinia carotovora
D) Fusarium sp.
Answer: A) Streptomyces scabies
Explanation: Soil actinomycete causing scabby lesions on potato tubers.
22. Angular leaf spot of beans is caused by:
A) Pseudomonas syringae pv. phaseolicola
B) Xanthomonas axonopodis pv. phaseoli
C) Fusarium oxysporum
D) Cercospora sp.
Answer: B) Xanthomonas axonopodis pv. phaseoli
Explanation: Produces angular water-soaked lesions on bean leaves.
23. Bacterial blight of cotton is caused by:
A) Xanthomonas citri
B) Xanthomonas axonopodis pv. malvacearum
C) Pseudomonas tabaci
D) Erwinia carotovora
Answer: B) Xanthomonas axonopodis pv. malvacearum
Explanation: Produces black lesions on cotton leaves and bolls.
24. A bacterial disease of banana is:
A) Moko disease (Ralstonia solanacearum)
B) Bunchy top (Virus)
C) Panama wilt (Fusarium)
D) Sigatoka (Fungus)
Answer: A) Moko disease (Ralstonia solanacearum)
Explanation: Bacterial wilt disease of banana caused by Ralstonia.
25. The bacterial pathogen causing gummosis in beans is:
A) Xanthomonas axonopodis
B) Pseudomonas syringae
C) Ralstonia solanacearum
D) Agrobacterium tumefaciens
Answer: B) Pseudomonas syringae
Explanation: Produces gum-like bacterial exudates on bean plants.
26. Rust of wheat is caused by:
A) Alternaria solani
B) Ustilago maydis
C) Puccinia graminis tritici
D) Fusarium oxysporum
Answer: C) Puccinia graminis tritici
Explanation: This fungus causes black rust of wheat, one of the most serious fungal diseases of cereals.
27. Loose smut of wheat is caused by:
A) Ustilago nuda tritici
B) Tilletia tritici
C) Puccinia graminis
D) Cercospora sp.
Answer: A) Ustilago nuda tritici
Explanation: Ustilago infects seeds internally, replacing grains with black smut spores.
28. Covered smut of wheat is caused by:
A) Tilletia caries
B) Ustilago avenae
C) Puccinia recondita
D) Alternaria alternata
Answer: A) Tilletia caries
Explanation: Tilletia causes covered smut/bunt, producing fishy odor in grains.
29. Ergot of rye is caused by:
A) Claviceps purpurea
B) Puccinia graminis
C) Phytophthora infestans
D) Cercospora personata
Answer: A) Claviceps purpurea
Explanation: It produces ergot alkaloids (ergotism in humans if consumed).
30. Tikka disease (leaf spot) of groundnut is caused by:
A) Cercospora arachidicola & C. personata
B) Fusarium oxysporum
C) Alternaria brassicae
D) Ustilago sp.
Answer: A) Cercospora arachidicola & C. personata
Explanation: Both fungi cause characteristic leaf spots, reducing yield.
31. Wilt of pigeon pea is caused by:
A) Fusarium udum
B) Xanthomonas citri
C) Alternaria alternata
D) Claviceps purpurea
Answer: A) Fusarium udum
Explanation: A soil-borne fungus causing vascular wilt in pigeon pea.
32. Downy mildew of grapes is caused by:
A) Phytophthora infestans
B) Plasmopara viticola
C) Erysiphe graminis
D) Alternaria sp.
Answer: B) Plasmopara viticola
Explanation: It is a fungus-like oomycete causing downy mildew in grape leaves and fruits.
33. Powdery mildew of pea is caused by:
A) Erysiphe pisi
B) Alternaria brassicae
C) Ustilago maydis
D) Cercospora personata
Answer: A) Erysiphe pisi
Explanation: White powdery patches on pea leaves and pods are due to Erysiphe.
34. Blast disease of rice is caused by:
A) Pyricularia oryzae (Magnaporthe grisea)
B) Puccinia graminis
C) Fusarium oxysporum
D) Cercospora oryzae
Answer: A) Pyricularia oryzae
Explanation: The most destructive rice disease worldwide.
35. Red rot of sugarcane is caused by:
A) Colletotrichum falcatum
B) Fusarium oxysporum
C) Alternaria tenuis
D) Cercospora personata
Answer: A) Colletotrichum falcatum
Explanation: A major fungal disease of sugarcane, causing reddish patches in stems.
36. Late blight of potato is caused by:
A) Phytophthora infestans
B) Alternaria solani
C) Fusarium oxysporum
D) Pythium debaryanum
Answer: A) Phytophthora infestans
Explanation: Responsible for the Irish potato famine of 1845.
37. Early blight of potato is caused by:
A) Alternaria solani
B) Phytophthora infestans
C) Cercospora solani
D) Colletotrichum sp.
Answer: A) Alternaria solani
Explanation: Causes concentric ring lesions on leaves and stems.
38. Charcoal rot of sorghum is caused by:
A) Macrophomina phaseolina
B) Sclerospora graminicola
C) Fusarium udum
D) Ustilago maydis
Answer: A) Macrophomina phaseolina
Explanation: Produces charcoal-like black microsclerotia in infected tissues.
39. Head smut of maize is caused by:
A) Ustilago maydis
B) Sphacelotheca reiliana
C) Puccinia recondita
D) Alternaria alternata
Answer: B) Sphacelotheca reiliana
Explanation: Replaces maize ears with smut sori.
40. Smut of corn (common smut) is caused by:
A) Ustilago maydis
B) Tilletia tritici
C) Fusarium oxysporum
D) Puccinia striiformis
Answer: A) Ustilago maydis
Explanation: Produces large tumor-like galls on maize plants.
41. Anthracnose of mango is caused by:
A) Colletotrichum gloeosporioides
B) Fusarium udum
C) Alternaria tenuis
D) Cercospora personata
Answer: A) Colletotrichum gloeosporioides
Explanation: Dark necrotic lesions on mango leaves, twigs, and fruits.
42. Green ear disease of bajra (pearl millet) is caused by:
A) Claviceps fusiformis
B) Sclerospora graminicola
C) Ustilago cynodontis
D) Fusarium moniliforme
Answer: B) Sclerospora graminicola
Explanation: Converts floral parts into leafy structures (green ears).
43. Coffee rust is caused by:
A) Hemileia vastatrix
B) Puccinia graminis
C) Cercospora coffeicola
D) Fusarium oxysporum
Answer: A) Hemileia vastatrix
Explanation: A serious fungal disease that destroyed coffee plantations in Sri Lanka.
44. Apple scab is caused by:
A) Venturia inaequalis
B) Fusarium sp.
C) Alternaria sp.
D) Ustilago sp.
Answer: A) Venturia inaequalis
Explanation: A fungal pathogen causing scabby lesions on apples.
45. Damping-off disease of seedlings is caused by:
A) Pythium debaryanum
B) Alternaria brassicae
C) Cercospora sp.
D) Ustilago sp.
Answer: A) Pythium debaryanum
Explanation: A soil-borne oomycete that rots young seedlings.
46. Rust of linseed is caused by:
A) Uromyces lini
B) Puccinia recondita
C) Fusarium lini
D) Alternaria lini
Answer: A) Uromyces lini
Explanation: A rust fungus affecting linseed crops.
47. Wilt of cotton is caused by:
A) Fusarium oxysporum f. sp. vasinfectum
B) Colletotrichum gloeosporioides
C) Alternaria solani
D) Cercospora gossypina
Answer: A) Fusarium oxysporum f. sp. vasinfectum
Explanation: Causes vascular wilt in cotton plants.
48. Fruit rot of chili is caused by:
A) Colletotrichum capsici
B) Alternaria alternata
C) Cercospora sp.
D) Puccinia sp.
Answer: A) Colletotrichum capsici
Explanation: Leads to fruit rotting and severe yield losses.
49. Leaf spot of turmeric is caused by:
A) Colletotrichum capsici
B) Alternaria alternata
C) Taphrina deformans
D) Cercospora zingiberi
Answer: D) Cercospora zingiberi
Explanation: Characteristic leaf spots leading to reduced photosynthesis.
50. Leaf blight of rice is caused by:
A) Helminthosporium oryzae (Bipolaris oryzae)
B) Puccinia oryzae
C) Colletotrichum oryzae
D) Alternaria oryzae
Answer: A) Helminthosporium oryzae (Bipolaris oryzae)
Explanation: Causes brown leaf spots and blight in rice fields.
51. The first plant disease proven to be caused by a virus was:
A) Bunchy top of banana
B) Mosaic of tobacco
C) Little leaf of brinjal
D) Yellow vein mosaic of bhindi
Answer: B) Mosaic of tobacco
Explanation: Tobacco mosaic virus (TMV) was the first virus discovered (by Ivanowsky, 1892; Beijerinck, 1898).
52. The causal agent of tobacco mosaic disease is:
A) TMV (virus)
B) Fungus
C) Bacterium
D) Mycoplasma
Answer: A) TMV (virus)
Explanation: TMV causes mottling, mosaic, and curling of tobacco leaves.
53. Bunchy top of banana is caused by:
A) Fungus
B) Virus
C) Mycoplasma
D) Bacterium
Answer: B) Virus
Explanation: Banana bunchy top virus (BBTV) causes stunted growth with leaves appearing bunched at the top.
54. Yellow vein mosaic of bhindi (okra) is transmitted by:
A) Aphids
B) Whiteflies (Bemisia tabaci)
C) Thrips
D) Leafhoppers
Answer: B) Whiteflies (Bemisia tabaci)
Explanation: The virus spreads via whiteflies, producing yellow vein patterns on okra leaves.
55. Leaf curl disease of chili is caused by:
A) Fungus
B) Bacterium
C) Virus
D) Mycoplasma
Answer: C) Virus
Explanation: Transmitted by whiteflies, it causes curling and puckering of chili leaves.
56. Little leaf of brinjal is caused by:
A) Virus
B) Fungus
C) Phytoplasma (mycoplasma-like organism)
D) Bacterium
Answer: C) Phytoplasma (MLO)
Explanation: Transmitted by leafhoppers, results in small, narrow leaves and stunted plants.
57. Spike disease of sandalwood is caused by:
A) Fungus
B) Virus
C) Phytoplasma
D) Bacterium
Answer: C) Phytoplasma
Explanation: Spike disease causes witches’ broom-like growth in sandalwood trees.
58. Phyllody in sesame is caused by:
A) Fungus
B) Virus
C) Phytoplasma
D) Bacterium
Answer: C) Phytoplasma
Explanation: Floral parts convert into leafy structures due to phytoplasma infection.
59. Which plant disease is caused by a viroid?
A) Mosaic of tobacco
B) Potato spindle tuber disease
C) Little leaf of brinjal
D) Yellow vein mosaic of bhindi
Answer: B) Potato spindle tuber disease
Explanation: Viroids are naked infectious RNA molecules discovered by T.O. Diener (1971).
60. Citrus greening disease is caused by:
A) Fungus
B) Virus
C) Phytoplasma-like organism
D) Nematode
Answer: C) Phytoplasma-like organism
Explanation: Also called Huanglongbing, spread by psyllid insects.
61. Witches’ broom in plants is usually caused by:
A) Viruses
B) Fungi
C) Phytoplasmas
D) Bacteria
Answer: C) Phytoplasmas
Explanation: Phytoplasmas alter plant growth leading to broom-like proliferation of shoots.
62. Groundnut rosette disease is caused by:
A) Fungus
B) Virus
C) Bacterium
D) Phytoplasma
Answer: B) Virus
Explanation: Groundnut rosette virus complex transmitted by aphids.
63. Leaf roll of potato is caused by:
A) Virus
B) Fungus
C) Bacterium
D) Mycoplasma
Answer: A) Virus
Explanation: Potato leaf roll virus causes upward rolling of potato leaves.
64. Grassy shoot disease of sugarcane is caused by:
A) Virus
B) Bacterium
C) Phytoplasma
D) Fungus
Answer: C) Phytoplasma
Explanation: Sugarcane grassy shoot is transmitted by leafhoppers.
65. Papaya ring spot disease is caused by:
A) Fungus
B) Virus
C) Bacterium
D) Phytoplasma
Answer: B) Virus
Explanation: Papaya ring spot virus (PRSV) produces mosaic, distortion, and ring-like spots on papaya leaves and fruits.
66. Mosaic disease of sugarcane is caused by:
A) Sugarcane mosaic virus (SCMV)
B) Fungus
C) Xanthomonas bacteria
D) Phytoplasma
Answer: A) Sugarcane mosaic virus (SCMV)
Explanation: Causes mosaic patterns and reduced cane yield.
67. Rugose leaf curl of tomato is caused by:
A) Virus
B) Fungus
C) Bacterium
D) Phytoplasma
Answer: A) Virus
Explanation: Tomato leaf curl virus transmitted by whiteflies.
68. A disease caused by both nematode and bacterium together is:
A) Citrus canker
B) Tundu disease of wheat
C) Potato spindle tuber disease
D) Coffee rust
Answer: B) Tundu disease of wheat
Explanation: Caused by Anguina tritici (nematode) + Clavibacter tritici (bacterium).
69. Bacterial wilt of banana (Moko disease) is often confused with:
A) Panama wilt (Fusarium)
B) Bunchy top (Virus)
C) Sigatoka (Fungus)
D) Red rot (Colletotrichum)
Answer: A) Panama wilt (Fusarium)
Explanation: Both cause wilting, but Moko is bacterial and Panama is fungal.
70. The disease Apple scar skin is caused by:
A) Fungus
B) Virus
C) Viroid
D) Bacterium
Answer: C) Viroid
Explanation: Caused by Apple scar skin viroid (ASSVd).
71. Onion yellow dwarf disease is caused by:
A) Fungus
B) Virus
C) Phytoplasma
D) Bacterium
Answer: B) Virus
Explanation: Onion yellow dwarf virus causes stunting and yellowing.
72. Which plant pathogen category lacks protein coat?
A) Virus
B) Fungus
C) Viroid
D) Bacterium
Answer: C) Viroid
Explanation: Viroids are naked RNA molecules without a protein coat.
73. Mosaic disease of bean is caused by:
A) Bean common mosaic virus
B) Cercospora sp.
C) Pseudomonas sp.
D) Fusarium sp.
Answer: A) Bean common mosaic virus
Explanation: Causes mottling and stunted growth in beans.
74. Chlorotic streak disease of sugarcane is caused by:
A) Virus
B) Fungus
C) Phytoplasma
D) Bacterium
Answer: A) Virus
Explanation: Chlorotic streak virus causes streaking and reduced sugarcane yield.
75. Viroids differ from viruses in:
A) Being smaller and lacking protein coat
B) Being DNA-based only
C) Causing animal diseases only
D) Having both RNA and DNA
Answer: A) Being smaller and lacking protein coat
Explanation: Viroids are the smallest infectious agents, consisting of naked RNA.
76. Red rot of sugarcane is caused by:
A) Colletotrichum falcatum
B) Fusarium oxysporum
C) Alternaria tenuis
D) Cercospora personata
Answer: A) Colletotrichum falcatum
Explanation: A major fungal disease of sugarcane producing red streaks inside stems.
77. Panama disease of banana is caused by:
A) Fusarium oxysporum f. sp. cubense
B) Ralstonia solanacearum
C) Phytophthora infestans
D) Ustilago maydis
Answer: A) Fusarium oxysporum f. sp. cubense
Explanation: A soil-borne fungus causing devastating wilt in bananas.
78. The Irish famine (1845) was due to:
A) Rice blast
B) Late blight of potato
C) Wheat rust
D) Citrus canker
Answer: B) Late blight of potato
Explanation: Phytophthora infestans destroyed potato crops in Ireland, causing mass starvation.
79. Green ear disease of bajra is caused by:
A) Claviceps fusiformis
B) Sclerospora graminicola
C) Ustilago cynodontis
D) Alternaria brassicae
Answer: B) Sclerospora graminicola
Explanation: Downy mildew fungus converts floral parts into leafy structures (green ears).
80. Which plant disease is caused by a viroid?
A) Mosaic of tobacco
B) Potato spindle tuber disease
C) Bunchy top of banana
D) Citrus canker
Answer: B) Potato spindle tuber disease
Explanation: Viroids are infectious naked RNA molecules, discovered by T.O. Diener (1971).
81. Coffee rust is caused by:
A) Puccinia graminis
B) Hemileia vastatrix
C) Colletotrichum coffeanum
D) Alternaria coffeicola
Answer: B) Hemileia vastatrix
Explanation: This fungus devastated coffee plantations in Sri Lanka in the 19th century.
82. Tundu disease of wheat is a complex disease caused by:
A) Fungus only
B) Virus only
C) Nematode + Bacterium
D) Phytoplasma
Answer: C) Nematode + Bacterium
Explanation: Caused by Anguina tritici (nematode) + Clavibacter tritici (bacterium).
83. Smut of corn (common smut) is caused by:
A) Ustilago maydis
B) Tilletia tritici
C) Fusarium udum
D) Puccinia recondita
Answer: A) Ustilago maydis
Explanation: Produces tumor-like galls filled with black spores on maize.
84. Blast disease of rice is caused by:
A) Alternaria solani
B) Pyricularia oryzae (Magnaporthe grisea)
C) Puccinia recondita
D) Claviceps fusiformis
Answer: B) Pyricularia oryzae
Explanation: The most destructive fungal disease of rice worldwide.
85. Apple scab is caused by:
A) Fusarium sp.
B) Venturia inaequalis
C) Cercospora sp.
D) Ustilago sp.
Answer: B) Venturia inaequalis
Explanation: A fungal pathogen causing scabby lesions on apple leaves and fruits.
86. Club root disease of cabbage is caused by:
A) Fusarium oxysporum
B) Plasmodiophora brassicae
C) Alternaria brassicae
D) Cercospora brassicicola
Answer: B) Plasmodiophora brassicae
Explanation: A protozoan-like pathogen that induces club-shaped swellings in roots.
87. Powdery mildew of pea is caused by:
A) Puccinia pisi
B) Erysiphe pisi
C) Ustilago pisi
D) Cercospora pisi
Answer: B) Erysiphe pisi
Explanation: White powdery coating on leaves and pods.
88. Damping-off of seedlings is caused by:
A) Pythium debaryanum
B) Fusarium udum
C) Alternaria solani
D) Cercospora arachidicola
Answer: A) Pythium debaryanum
Explanation: A soil-borne oomycete that infects young seedlings, causing collapse.
89. Rust of linseed is caused by:
A) Uromyces lini
B) Puccinia graminis
C) Cercospora lini
D) Fusarium lini
Answer: A) Uromyces lini
Explanation: Produces rust pustules on linseed.
90. Sigatoka disease of banana is caused by:
A) Mycosphaerella musicola
B) Fusarium oxysporum
C) Phytophthora infestans
D) Alternaria brassicae
Answer: A) Mycosphaerella musicola
Explanation: A leaf spot disease of banana.
91. Red leaf spot of turmeric is caused by:
A) Colletotrichum capsici
B) Cercospora zingiberi
C) Taphrina deformans
D) Puccinia zingiberi
Answer: B) Cercospora zingiberi
Explanation: Causes reddish leaf spots in turmeric plants.
92. Which plant disease is caused by Phytoplasma?
A) Phyllody of sesame
B) Tobacco mosaic
C) Citrus canker
D) Red rot of sugarcane
Answer: A) Phyllody of sesame
Explanation: Phytoplasmas convert floral parts into leafy structures.
93. Which disease of sandalwood is caused by Phytoplasma?
A) Wilt
B) Spike disease
C) Anthracnose
D) Powdery mildew
Answer: B) Spike disease
Explanation: Causes witches’ broom-like growth and sterility in sandalwood.
94. Which disease of papaya is caused by a virus?
A) Ring spot disease
B) Wilt disease
C) Red rot disease
D) Blight
Answer: A) Ring spot disease
Explanation: Papaya ring spot virus causes circular mottling on leaves and fruits.
95. Groundnut rosette disease is transmitted by:
A) Whiteflies
B) Aphids
C) Thrips
D) Leafhoppers
Answer: B) Aphids
Explanation: Groundnut rosette virus is spread by Aphis craccivora.
96. Witches’ broom disease of legumes is caused by:
A) Virus
B) Fungus
C) Phytoplasma
D) Nematode
Answer: C) Phytoplasma
Explanation: Phytoplasma infection leads to excessive shoot proliferation.
97. Black rot of crucifers is caused by:
A) Xanthomonas campestris pv. campestris
B) Fusarium brassicae
C) Alternaria brassicae
D) Cercospora brassicicola
Answer: A) Xanthomonas campestris pv. campestris
Explanation: A bacterial disease producing characteristic V-shaped leaf lesions.
98. The causal organism of bunt disease of wheat is:
A) Tilletia caries
B) Ustilago nuda
C) Puccinia graminis
D) Alternaria alternata
Answer: A) Tilletia caries
Explanation: Produces “stinking smut” with fishy odor due to trimethylamine.
99. The disease “soft rot of carrot” is caused by:
A) Erwinia carotovora
B) Fusarium oxysporum
C) Pythium debaryanum
D) Colletotrichum sp.
Answer: A) Erwinia carotovora
Explanation: A bacterial disease causing watery soft rot of carrots and other vegetables.
100. Which is the causal organism of loose smut of wheat?
A) Tilletia tritici
B) Ustilago nuda tritici
C) Puccinia graminis tritici
D) Fusarium oxysporum
Answer: B) Ustilago nuda tritici
Explanation: A seed-borne fungus replacing wheat grains with black powdery spores.