Question

Arrange the following components in chronological order of their development during infection
(A). Spore
(B). Appressorium
(C). Infection Hypha
(D). Germtube

• A. (A), (B), (D), (C)
• B. (A), (D), (B), (C)
• C. (B), (A), (D), (C)
• D. (C), (B), (D), (A)

Hint:

Remember the path of infection: first, the spore lands (A), then it germinates (D), forms a pressurized appressorium (B), and finally penetrates with an infection hypha (C).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Fungal pathogenesis involves a highly coordinated sequence of developmental steps on the plant host surface to facilitate successful penetration and colonization.

Step 2: Detailed Explanation:
Let us follow the chronological stages of a typical fungal foliar pathogen establishing infection:
1. Spore (A): The process begins with the physical deposition of a fungal propagule (spore) onto the host cuticle.
2. Germtube (D): Under favorable moisture and temperature conditions, the spore hydrates and germinates, producing a tubular outgrowth called a germtube.
3. Appressorium (B): Upon sensing physical cues (surface contact) or chemical cues from the host, the tip of the germtube stops growing and expands into a specialized, dome-shaped infection structure called an appressorium.
The appressorium firmly adheres to the plant surface and accumulates high concentrations of glycerol to generate immense osmotic turgor pressure.
4. Infection Hypha (C): Using this mechanical turgor pressure along with cell-wall-degrading enzymes, a narrow penetration peg develops from the base of the appressorium.
This peg breaches the plant cell wall and develops into an infection hypha inside the host tissue to absorb nutrients.
Therefore, the correct chronological order is: Spore (A) \(\rightarrow\) Germtube (D) \(\rightarrow\) Appressorium (B) \(\rightarrow\) Infection Hypha (C).

Step 3: Final Answer:
The correct option is (B) (A), (D), (B), (C).