In applying Koch’s postulates to a plant disease, which step comes first?
Correct answer A. The suspected pathogen must be found associated with every diseased plant
Topic / 34 questions
Plant Pathology MCQs
Plant Pathology MCQs cover the study of plant diseases, the organisms that cause them and related microbiology, such as fungi, bacteria and nitrifying microbes. They help agriculture students and candidates for Agriculture Officer, PPSC and ICAR exams. Each question has an instant answer, so you can check disease and pathogen facts quickly.
Ascochyta blight, a major disease of chickpea (gram) in Pakistan, is caused by which fungus?
Correct answer C. Ascochyta rabiei
Wilt of chickpea is caused by which soil-borne fungus?
Correct answer C. Fusarium oxysporum f. sp. ciceris
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Panama disease of banana is a vascular wilt caused by which fungus?
Correct answer C. Fusarium oxysporum f. sp. cubense
Citrus canker, causing raised corky lesions on leaves and fruit, is caused by which type of pathogen?
Correct answer C. Bacterium
Citrus greening (huanglongbing) is spread in the field mainly by which insect?
Correct answer C. Asian citrus psyllid
What is the genetic material of Tobacco mosaic virus?
Correct answer A. Single-stranded RNA
Potato spindle tuber disease is caused by which type of agent?
Correct answer C. Viroid
Sesame phyllody, in which flowers turn into leafy structures, is caused by which agent?
Correct answer A. Phytoplasma
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Cotton leaf curl disease in Pakistan is caused by a begomovirus transmitted by which vector?
Correct answer A. Whitefly (Bemisia tabaci)
Which step completes Koch’s postulates for proving that a fungus causes a plant disease?
Correct answer C. Re-isolating the same organism from artificially inoculated plants
Bordeaux mixture, one of the earliest fungicides, is prepared from which ingredients?
Correct answer B. Copper sulphate and lime
The disease triangle in plant pathology consists of which three components?
Correct answer B. Susceptible host, virulent pathogen and favourable environment
Damping-off of seedlings in nurseries is most commonly caused by which genus?
Correct answer B. Pythium
Green ear (downy mildew) disease of pearl millet is caused by which organism?
Correct answer D. Sclerospora graminicola
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Crown gall, which produces tumour-like swellings on many dicot plants, is caused by which bacterium?
Correct answer D. Agrobacterium tumefaciens
Root-knot disease of vegetables, marked by galls on roots, is caused by which organism?
Correct answer B. Meloidogyne nematodes
Red rot of sugarcane is caused by which fungus?
Correct answer B. Colletotrichum falcatum
Because loose smut of wheat is internally seed-borne, which control method is most effective?
Correct answer D. Seed treatment with a systemic fungicide
Black (stem) rust of wheat is caused by which fungus?
Correct answer B. Puccinia graminis tritici
About Plant Pathology MCQs
Plant pathology deals with diseases caused by fungi, bacteria, viruses and nematodes, and with how they are diagnosed and controlled. Questions in this set ask which disease Erysiphe causes, which microbe converts ammonia into nitrite in the soil, which organisms are gram-positive, and where coprophilic fungi live. Erysiphe causes powdery mildew, Nitrosomonas carries out the first step of nitrification, and coprophilic fungi grow on animal dung. These short pathogen and microbiology facts are common in agriculture officer, subject specialist and agricultural university entrance tests.
Exams that include Plant Pathology MCQs
Pakistan
- PPSC
- Agriculture Officer tests
- Lecturer tests
- NTS
India
- ICAR AIEEA
- UGC NET
- State PSC exams
Bangladesh
- BCS
- University admission tests (DU, RU, JU)
Frequently asked questions
Which disease is caused by Erysiphe?
Erysiphe is a fungus that causes powdery mildew, a disease that forms a white, powdery coating on leaves, stems and sometimes fruit. It affects crops such as peas, cereals and cucurbits, and it is usually managed with resistant varieties and sulphur-based fungicides.
Which microbe converts ammonia into nitrite?
Nitrosomonas bacteria convert ammonia into nitrite in the first step of nitrification. Nitrobacter then converts nitrite into nitrate, which plants can absorb. This process is important for soil fertility and is a common exam question in agriculture tests.
Last reviewed October 2026