(A) P-3-i, Q-1-iv, R-2-iii, S-4-ii

(B) P-3-ii, Q-1-iv, R-4-i, S-2-iii

(C) P-4-ii, Q-1-i, R-3-iv, S-2-iii

(D) P-2-iii, Q-3-ii, R-1-iv, S-4-i

Option (B) is correct: P-3-ii, Q-1-iv, R-4-i, S-2-iii.

Correct Matches

• P. Powdery mildew: 3. Erysiphe orontii (ii. Tomato) – Erysiphe orontii causes powdery mildew on tomato, producing white powdery growth on leaves.​

• Q. White rust: 1. Albugo candida (iv. Mustard) – Albugo candida causes white rust on mustard and other crucifers, forming white pustules on leaves.​

• R. Downy mildew: 4. Peronoscleropora philippinensis (i. Corn) – Peronoscleropora philippinensis (Philippine downy mildew) affects corn, causing yellow stripes and downy growth.​

• S. Late blight: 2. Phytophthora infestans (iii. Potato) – Phytophthora infestans causes late blight primarily on potato, leading to blighted leaves and tubers.​

Option Analysis

• (A) P-3-i, Q-1-iv, R-2-iii, S-4-ii: Incorrect. P-3 matches organism but wrong crop (corn, not tomato); R-2 wrong organism (Phytophthora for downy mildew on potato); S-4 wrong organism/crop.

• (B) P-3-ii, Q-1-iv, R-4-i, S-2-iii: Correct, as detailed above.​

• (C) P-4-ii, Q-1-i, R-3-iv, S-2-iii: Incorrect. P-4 wrong organism (downy mildew agent on tomato); Q-1 wrong crop (corn); R-3 wrong (powdery mildew agent on mustard).

• (D) P-2-iii, Q-3-ii, R-1-iv, S-4-i: Incorrect. P-2 wrong (late blight on potato); Q-3 wrong (powdery mildew on tomato); R-1 wrong (white rust agent).​

Powdery mildew, white rust, downy mildew, and late blight rank among key fungal diseases impacting crops like corn, tomato, potato, and mustard in agriculture exams such as CSIR NET Life Sciences. These oomycete and fungal pathogens cause significant yield losses, making accurate matching of disease, causative organism, and affected crop essential for students and farmers. Understanding their symptoms, cycles, and hosts aids in disease management and exam success.​

Disease Profiles

• Powdery Mildew (Erysiphe orontii): White powdery fungal growth on tomato leaves; thrives in warm, dry conditions.​

• White Rust (Albugo candida): Raised white pustules on mustard (crucifers); cool, wet weather favors spread.​

• Downy Mildew (Peronoscleropora philippinensis): Yellow streaks and downy patches under corn leaves; seedborne in maize.​

• Late Blight (Phytophthora infestans): Dark lesions on potato foliage/tubers; rapid spread in humid conditions.​

Crop Impacts

These diseases reduce photosynthesis and yield: powdery mildew up to 45% in tomato/mustard, white rust deforms mustard leaves, downy mildew devastates corn (40-100% loss), late blight historically caused famines in potato.​

Exam Strategies

For CSIR NET, memorize pairings: Erysiphe-tomato (P-3-ii), Albugo-mustard (Q-1-iv), Peronoscleropora-corn (R-4-i), Phytophthora-potato (S-2-iii). Practice options elimination based on known hosts. Resistant varieties and fungicides like mefenoxam control spread.