PRELIMS

Plant Pathology and Botany Records

Biological diseases and environmental records explain the extremes and vulnerabilities of the plant kingdom.

I. Major Plant Diseases

• Viral: Disease: Mosaic of Tobacco. Cause / Symptoms: TMV (Tobacco Mosaic Virus); leaves shrink/small.
• ****: Disease: Bunchy top of Banana. Cause / Symptoms: Banana virus; leaves accumulated like a rose.
• Bacterial: Disease: Wilt of Potato. Cause / Symptoms: Pseudomonas solanacearum; Ring disease (brown ring on xylem).
• ****: Disease: Black Arm of Cotton. Cause / Symptoms: Xanthomonas; brown water bodies on leaves.
• ****: Disease: Citrus Canker. Cause / Symptoms: Xanthomonas citri; affects leaves, branches, fruits.
• ****: Disease: Tundu Disease. Cause / Symptoms: Wheat disease; factors are nematode/bacteria.
• Fungal: Disease: Red Rot. Cause / Symptoms: Sugarcane.
• ****: Disease: Tikka Disease. Cause / Symptoms: Groundnut.
• ****: Disease: Ergot. Cause / Symptoms: Bajra; caused by Claviceps purpurea.
• ****: Disease: Late Blight of Potato. Cause / Symptoms: Phytophthora infestans; triggered the Irish Potato Famine (1840s).
• ****: Disease: Rust of Wheat. Cause / Symptoms: Puccinia fungus; reddish-brown pustules on leaves/stem.
• ****: Disease: Powdery Mildew. Cause / Symptoms: Fungal; white powdery coating on leaves (affects many crops).
• ****: Disease: Damping Off. Cause / Symptoms: Pythium; rots seedlings at soil level in nurseries.

II. Botanical Superlatives and Records

• Longest Tree: Plant Name: Sequoia gigantea. Notes: Gymnosperm; Redwood of California; 120m height.
• Largest Angiosperm Tree: Plant Name: Eucalyptus. Notes: Highest among flowering plants.
• Smallest (in shape): Plant Name: Lemna. Notes: Aquatic angiosperm.
• Plant with Largest Leaf: Plant Name: Victoria regia. Notes: Aquatic plant (found in West Bengal).
• Largest Fruit / Seed: Plant Name: Lodoicea. Notes: Double coconut.
• Smallest Seed: Plant Name: Orchid. Notes: Microscopic seeds.
• Smallest Flower: Plant Name: Wolffia. Notes: Diameter of ~0.1 mm.
• Largest Flower: Plant Name: Rafflesia. Notes: Diameter of ~1 meter.
• Smallest Angiosperm: Plant Name: Wolffia. Notes: Also the host of the smallest flower.

III. Other High-Yield Botanical Facts

• Edible Part of Apple: Fleshy Thalamus.
• Space Algae: Chlorella.
• Father of Botany: Theophrastus.
• N-Fixation: Anabaena and Nostoc (Cyanobacteria).

IV. Confused Pairs — Pathogen Type Identification

• Virus vs Bacteria: Viral diseases are named with "Mosaic"/"Bunchy top" (TMV, Banana virus); bacterial diseases often carry genus names like Xanthomonas (Citrus Canker, Black Arm) or Pseudomonas (Potato Wilt).
• Fungal vs Viral confusion: Red Rot, Rust, Ergot, Tikka, and Late Blight are all fungal, not viral — a common Prelims trap.
• Damping Off vs Wilt: Damping Off kills seedlings at the soil line (Pythium); Wilt (Potato) causes vascular ring rot in mature plants (Pseudomonas solanacearum).

UPSC Relevance

Botany records and pathology are classic "General Science" themes in UPSC Prelims.

• Disease Identification: Differentiating between TMV (Virus) and Citrus Canker (Bacteria) is common.
• Agronomy: The economic impact of diseases like "Red Rot" in Sugarcane or "Potato Wilt" in agriculture.
• Superlatives: While basic, identifying the largest flower (Rafflesia) or smallest angiosperm (Wolffia) is recurrent in various competitive exams.