Match the name of the disease with the causal organism.DiseaseCausal organismP. Black rot of sugarcane1. Cercospora personataQ. Stem rot of jute2. Macrophomina phaseolinaR. Tikka disease of groundnut3. Ceratocystis adiposaS. Crown gall of grapes4. Synchytrium endobioticum5. Agrobacterium tumefaciens6. Colletotrichum corchorum

The correct match is P-3, Q-2, R-1, S-5.Black rot of sugarcane is caused by Ceratocystis adiposa (P-3).Stem rot (charcoal rot) of jute is caused by Macrophomina phaseolina (Q-2).Tikka (leaf spot) disease of groundnut is caused by Cercospora, including C. personata (R-1).Crown gall of grapes is caused by Agrobacterium tumefaciens (S-5).Synchytrium endobioticum causes wart disease of potato and Colletotrichum corchorum causes anthracnose of jute, so options using 4 or 6 are wrong, and A and B misplace the Cercospora and Macrophomina diseases.

Match Group I (plant disease), Group II (causal organism) and Group III (affected plant) in CORRECT combination.Group-IGroup-IIGroup-IIIP. Karnal BuntI. Phytophthora infestansa. RiceQ. ErgotII. Blumeria graminisb. PotatoR. Late blightIII. Neovossia indicac. RyeS. Powdery mildewIV. Puccinia reconditad. WheatV. Claviceps purpureae. BarleyVI. Alternaria solanif. Brinjal

The correct combination is P-III-d, Q-V-c, R-I-b, S-II-e.Karnal bunt of wheat (d) is caused by Neovossia indica (III), also called Tilletia indica, first reported from Karnal, Haryana.Ergot is caused by Claviceps purpurea (V), and rye (c) is its classic host.Late blight of potato (b) is caused by the oomycete Phytophthora infestans (I), the agent of the Irish famine.Powdery mildew of barley (e) is caused by Blumeria graminis (II).The leftovers are distractors: Puccinia recondita causes brown (leaf) rust of cereals, and Alternaria solani causes early blight of potato and tomato. Option B assigns late blight to Blumeria and powdery mildew to a rust, and options A and D misplace Karnal bunt.

Correctly match the following plant diseases in Group-I with their causal organisms in Group-II.Group-IGroup-II(P) Red rot of sugarcane(1) Albugo candida(Q) Tikka disease of groundnut(2) Cercospora personata(R) Late blight of potato(3) Plasmodiophora brassicae(S) White rust of mustard(4) Phytophthora infestans(5) Colletotrichum falcatum

The correct matching is P-5; Q-2; R-4; S-1.Red rot of sugarcane is caused by Colletotrichum falcatum (5).Tikka (leaf spot) disease of groundnut is caused by Cercospora personata (2), with C. arachidicola causing the early leaf spot.Late blight of potato, behind the Irish famine, is caused by Phytophthora infestans (4).White rust of mustard and other crucifers is caused by Albugo candida (1).Plasmodiophora brassicae (3) is the distractor: it causes club root of crucifers, not any disease in the list. The first option gives red rot to Albugo and white rust to Plasmodiophora, the second swaps the tikka and white rust pathogens, and the last gives tikka to Plasmodiophora and late blight to Albugo.

Plant Pathology Questions and Answers

Q: Match the following rice diseases in Group I with their causal agents in Group II.Group I: (P) Blast; (Q) False smut; (R) Sheath blight; (S) Downy mildewGroup II: (1) Sclerophthora macrospora; (2) Rhizoctonia solani; (3) Ustilaginoidea virens; (4) Puccinia graminis; (5) Magnaporthe grisea

The match is P-5; Q-3; R-2; S-1.Rice blast is caused by the fungus Magnaporthe grisea (Magnaporthe oryzae, anamorph Pyricularia).False smut, which turns grains into greenish smut balls, is caused by Ustilaginoidea virens.Sheath blight is caused by Rhizoctonia solani.Downy mildew of rice is caused by the oomycete Sclerophthora macrospora.Puccinia graminis, the stem rust of wheat, is the distractor: it does not cause any of these rice diseases, so every option using item 4 is wrong.

Q: Which one of the following agents causes the necrotic ring spot disease in stone fruits?

Necrotic ring spot of stone fruits is caused by a virus.The disease is caused by Prunus necrotic ringspot virus, an ilarvirus that infects cherry, peach, plum, almond and other Prunus species. It produces necrotic rings and spots on the leaves, often with shot-holes as the dead tissue drops out, and it spreads through infected pollen, seed and grafted budwood.Fungi, bacteria and nematodes cause other diseases of stone fruits, such as brown rot (a fungus) or bacterial canker, but not this ringspot disease, whose name refers to the viral symptoms.

Q: Which one of the following commercial products is used as a systemic fungicide to control plant diseases?

The systemic fungicide is Benomyl.Benomyl, a benzimidazole, is absorbed by the plant and moved within it, so it protects new growth and can act on infections already inside the tissue. It works by binding fungal beta-tubulin and blocking mitosis.Captan and Phaltan (folpet) are phthalimide fungicides and Thiram is a dithiocarbamate. All three are contact, protective fungicides: they stay on the surface where they are sprayed and kill spores before infection, but they are not translocated through the plant.

Q: The major ingredient of Bordeaux mixture is :

The major ingredient of Bordeaux mixture is copper sulphate.Bordeaux mixture, developed by Pierre-Marie-Alexis Millardet in France in the 1880s against downy mildew of grapes, is made by mixing copper sulphate solution with slaked lime (calcium hydroxide). The copper ions are the fungicide; the lime neutralises the solution so it does not scorch the leaves. A common strength is 1 per cent, made from equal weights of copper sulphate and lime.Potassium chloride, magnesium sulphate (spelt Megnesium in the paper) and ammonium nitrate (spelt Ammoniun) are fertilisers, not ingredients of this fungicide.

Q: The causal organism for rice blast disease is ...............................

Rice blast is caused by Magnaporthe grisea.Rice blast, the most destructive fungal disease of rice, is caused by the ascomycete Magnaporthe grisea (the rice pathogen is now often called Magnaporthe oryzae; its asexual state is Pyricularia). It forms diamond-shaped leaf lesions and can rot the panicle neck. The fungus breaks into leaves with a melanised appressorium under great turgor pressure.Xanthomonas oryzae causes bacterial leaf blight, Rhizoctonia solani causes sheath blight, and Helminthosporium oryzae causes brown spot, the disease behind the Bengal famine of 1943.

Q: Downy mildew is the most destructive fungal disease of grapevines and is caused by :

Downy mildew of grapevine is caused by Plasmopara viticola.This oomycete (traditionally studied with fungi) appeared in Europe from North America in the 1870s and devastated vineyards; the search for a control led to Bordeaux mixture, discovered by Millardet in 1882. It produces oily spots on the upper leaf surface and white downy sporulation beneath.The other pathogens attack different crops: Ascochyta rabiei causes Ascochyta blight of chickpea, Puccinia striiformis causes stripe (yellow) rust of wheat, and Sclerospora graminicola causes downy mildew (green ear) of pearl millet, not of grapevine.

Match the name of the disease with the causal organism.

Disease	Causal organism
P. Black rot of sugarcane	1. Cercospora personata
Q. Stem rot of jute	2. Macrophomina phaseolina
R. Tikka disease of groundnut	3. Ceratocystis adiposa
S. Crown gall of grapes	4. Synchytrium endobioticum
	5. Agrobacterium tumefaciens
	6. Colletotrichum corchorum

A.P-1, Q-3, R-6, S-5
B.P-2, Q-3, R-1, S-5
C.P-3, Q-2, R-1, S-5
D.P-2, Q-6, R-3, S-4

Exam Year(s)

GATE Life Sciences - 2012,

Answer: C

The correct match is P-3, Q-2, R-1, S-5.

Black rot of sugarcane is caused by Ceratocystis adiposa (P-3).
Stem rot (charcoal rot) of jute is caused by Macrophomina phaseolina (Q-2).
Tikka (leaf spot) disease of groundnut is caused by Cercospora, including C. personata (R-1).
Crown gall of grapes is caused by Agrobacterium tumefaciens (S-5).

Synchytrium endobioticum causes wart disease of potato and Colletotrichum corchorum causes anthracnose of jute, so options using 4 or 6 are wrong, and A and B misplace the Cercospora and Macrophomina diseases.

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Match Group I (plant disease), Group II (causal organism) and Group III (affected plant) in CORRECT combination.

Group-I	Group-II	Group-III
P. Karnal Bunt	I. Phytophthora infestans	a. Rice
Q. Ergot	II. Blumeria graminis	b. Potato
R. Late blight	III. Neovossia indica	c. Rye
S. Powdery mildew	IV. Puccinia recondita	d. Wheat
	V. Claviceps purpurea	e. Barley
	VI. Alternaria solani	f. Brinjal

A.P-II-a, Q-V-b, R-III-d, S-I-e
B.P-III-d, Q-V-c, R-II-e, S-IV-f
C.P-III-d, Q-V-c, R-I-b, S-II-e
D.P-V-c, Q-I-d, R-VI-b, S-II-e

Exam Year(s)

GATE Life Sciences - 2022,

Answer: C

The correct combination is P-III-d, Q-V-c, R-I-b, S-II-e.

Karnal bunt of wheat (d) is caused by Neovossia indica (III), also called Tilletia indica, first reported from Karnal, Haryana.
Ergot is caused by Claviceps purpurea (V), and rye (c) is its classic host.
Late blight of potato (b) is caused by the oomycete Phytophthora infestans (I), the agent of the Irish famine.
Powdery mildew of barley (e) is caused by Blumeria graminis (II).

The leftovers are distractors: Puccinia recondita causes brown (leaf) rust of cereals, and Alternaria solani causes early blight of potato and tomato. Option B assigns late blight to Blumeria and powdery mildew to a rust, and options A and D misplace Karnal bunt.

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Although Pseudomonas syringae infection in plants is actively inhibited by the endogenous salicylic acid (SA) of host origin, a successful infection is still established because the bacterium secretes coronatine, an effector molecule. Which one of the following best describes the mode of action of coronatine?

A.Coronatine inhibits SA biosynthesis.
B.Coronatine promotes the biosynthesis of jasmonic acid (JA), and JA signaling in turn inhibits SA response.
C.Coronatine is a structural analogue of SA, which binds to the SA receptor and inhibits its function.
D.Coronatine is a structural analogue of jasmonic acid (JA), which activates JA signaling to inhibit SA response.

Exam Year(s)

GATE Life Sciences - 2023,

Answer: D

Coronatine is a structural analogue of jasmonic acid (JA), which activates JA signaling to inhibit SA response.

Coronatine closely mimics the active hormone jasmonoyl-isoleucine (JA-Ile). It binds the COI1-JAZ co-receptor, triggers degradation of the JAZ repressors and switches on jasmonate signalling. Because the JA and SA pathways antagonise each other, activating JA signalling suppresses the SA-dependent defences that would otherwise restrict Pseudomonas syringae, and coronatine also reopens stomata for bacterial entry.

Coronatine does not act as an SA analogue or by directly blocking SA biosynthesis, and it does not work by raising the plant's own JA synthesis; it is itself the JA mimic.

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Match the following rice diseases in Group I with their causal agents in Group II.

Group I: (P) Blast; (Q) False smut; (R) Sheath blight; (S) Downy mildew

Group II: (1) Sclerophthora macrospora; (2) Rhizoctonia solani; (3) Ustilaginoidea virens; (4) Puccinia graminis; (5) Magnaporthe grisea

A.P-5; Q-3; R-2; S-1
B.P-4; Q-2; R-5; S-3
C.P-4; Q-5; R-3; S-1
D.P-5; Q-4; R-1; S-2

Exam Year(s)

GATE Life Sciences - 2023,

Answer: A

The match is P-5; Q-3; R-2; S-1.

Rice blast is caused by the fungus Magnaporthe grisea (Magnaporthe oryzae, anamorph Pyricularia).
False smut, which turns grains into greenish smut balls, is caused by Ustilaginoidea virens.
Sheath blight is caused by Rhizoctonia solani.
Downy mildew of rice is caused by the oomycete Sclerophthora macrospora.

Puccinia graminis, the stem rust of wheat, is the distractor: it does not cause any of these rice diseases, so every option using item 4 is wrong.

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Which one of the following agents causes the necrotic ring spot disease in stone fruits?

A.Fungi
B.Bacteria
C.Virus
D.Nematodes

Exam Year(s)

GATE Life Sciences - 2025,

Answer: C

Necrotic ring spot of stone fruits is caused by a virus.

The disease is caused by Prunus necrotic ringspot virus, an ilarvirus that infects cherry, peach, plum, almond and other Prunus species. It produces necrotic rings and spots on the leaves, often with shot-holes as the dead tissue drops out, and it spreads through infected pollen, seed and grafted budwood.

Fungi, bacteria and nematodes cause other diseases of stone fruits, such as brown rot (a fungus) or bacterial canker, but not this ringspot disease, whose name refers to the viral symptoms.

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Which one of the following commercial products is used as a systemic fungicide to control plant diseases?

A.Captan
B.Phaltan
C.Thiram
D.Benomyl

Exam Year(s)

GATE Life Sciences - 2026,

Answer: D

The systemic fungicide is Benomyl.

Benomyl, a benzimidazole, is absorbed by the plant and moved within it, so it protects new growth and can act on infections already inside the tissue. It works by binding fungal beta-tubulin and blocking mitosis.

Captan and Phaltan (folpet) are phthalimide fungicides and Thiram is a dithiocarbamate. All three are contact, protective fungicides: they stay on the surface where they are sprayed and kill spores before infection, but they are not translocated through the plant.

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Correctly match the following plant diseases in Group-I with their causal organisms in Group-II.

Group-I	Group-II
(P) Red rot of sugarcane	(1) Albugo candida
(Q) Tikka disease of groundnut	(2) Cercospora personata
(R) Late blight of potato	(3) Plasmodiophora brassicae
(S) White rust of mustard	(4) Phytophthora infestans
	(5) Colletotrichum falcatum

A.P-1; Q-2; R-4; S-3
B.P-5; Q-1; R-4; S-2
C.P-5; Q-2; R-4; S-1
D.P-5; Q-3; R-1; S-2

Exam Year(s)

GATE Life Sciences - 2026,

Answer: C

The correct matching is P-5; Q-2; R-4; S-1.

Red rot of sugarcane is caused by Colletotrichum falcatum (5).
Tikka (leaf spot) disease of groundnut is caused by Cercospora personata (2), with C. arachidicola causing the early leaf spot.
Late blight of potato, behind the Irish famine, is caused by Phytophthora infestans (4).
White rust of mustard and other crucifers is caused by Albugo candida (1).

Plasmodiophora brassicae (3) is the distractor: it causes club root of crucifers, not any disease in the list. The first option gives red rot to Albugo and white rust to Plasmodiophora, the second swaps the tikka and white rust pathogens, and the last gives tikka to Plasmodiophora and late blight to Albugo.

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The major ingredient of Bordeaux mixture is :

A.Potassium chloride
B.Copper sulphate
C.Megnesium sulphate
D.Ammoniun nitrate

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The major ingredient of Bordeaux mixture is copper sulphate.

Bordeaux mixture, developed by Pierre-Marie-Alexis Millardet in France in the 1880s against downy mildew of grapes, is made by mixing copper sulphate solution with slaked lime (calcium hydroxide). The copper ions are the fungicide; the lime neutralises the solution so it does not scorch the leaves. A common strength is 1 per cent, made from equal weights of copper sulphate and lime.

Potassium chloride, magnesium sulphate (spelt Megnesium in the paper) and ammonium nitrate (spelt Ammoniun) are fertilisers, not ingredients of this fungicide.

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The causal organism for rice blast disease is ...............................

A.Xanthomonas oryzae
B.Magnaporthe grisea
C.Rhizoctonia solani
D.Helminthosporium oryzae

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: B

Rice blast is caused by Magnaporthe grisea.

Rice blast, the most destructive fungal disease of rice, is caused by the ascomycete Magnaporthe grisea (the rice pathogen is now often called Magnaporthe oryzae; its asexual state is Pyricularia). It forms diamond-shaped leaf lesions and can rot the panicle neck. The fungus breaks into leaves with a melanised appressorium under great turgor pressure.

Xanthomonas oryzae causes bacterial leaf blight, Rhizoctonia solani causes sheath blight, and Helminthosporium oryzae causes brown spot, the disease behind the Bengal famine of 1943.

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10.

Downy mildew is the most destructive fungal disease of grapevines and is caused by :

A.Plasmopara viticola
B.Ascochyta rabiei
C.Puccinia striiformis
D.Sclerospora graminicola

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

Downy mildew of grapevine is caused by Plasmopara viticola.

This oomycete (traditionally studied with fungi) appeared in Europe from North America in the 1870s and devastated vineyards; the search for a control led to Bordeaux mixture, discovered by Millardet in 1882. It produces oily spots on the upper leaf surface and white downy sporulation beneath.

The other pathogens attack different crops: Ascochyta rabiei causes Ascochyta blight of chickpea, Puccinia striiformis causes stripe (yellow) rust of wheat, and Sclerospora graminicola causes downy mildew (green ear) of pearl millet, not of grapevine.

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