Question

Small pustules of spores that may be dusty or compact and red, brown, yellow, or black in colour, is known as .....................

• A. Rust
• B. Mildew
• C. Smut
• D. Blotch

Hint:

Rust diseases are highly destructive to cereals like wheat (e.g., black stem rust, yellow stripe rust) and are named 'rust' because the orange-brown spore pustules resemble oxidized iron rust.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Plant diseases caused by fungal pathogens present distinct visual symptoms on host tissues.
Identifying these characteristic fungal structures helps diagnose diseases in field crops.

Step 2: Detailed Explanation:
Let us define the characteristic symptoms of the diseases listed:
1. Rust: This is a fungal disease caused by species belonging to the order Pucciniales (such as *Puccinia graminis*).
The most classic symptom is the appearance of small, raised pustules (uredinia) on leaves or stems.
These pustules contain a dusty mass of spores that are commonly orange, red, rust-brown, yellow, or black in color.
When touched, these spores easily rub off as a fine dust.
2. Mildew: This presents as a powdery or downy growth on plant leaves (e.g., powdery mildew, downy mildew), usually white or grayish, rather than distinct compact colored pustules.
3. Smut: This is characterized by large, soot-like black spore masses that typically replace the grains or floral structures (e.g., loose smut of wheat).
4. Blotch: This appears as large, flat, irregular necrotic patches on leaf or stem tissues, often associated with bacterial or septoria infections, lacking powdery pustules.

Step 3: Final Answer:
Small pustules of dusty spores in shades of red, brown, yellow, or black are characteristic of Rust, corresponding to option (A).