1. The study of plant diseases is called ____________.
A) Mycology
B) Pathology
C) Phytopathology
D) Agronomy
Answer: C
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Explanation: A seed-borne fungus replacing wheat grains with black powdery spores.