Question

Sequence of pathogenesis events:
A. Invasion
B. Dissemination
C. Reproduction
D. Infection
E. Inoculation
F. Penetration
Choose the correct sequence from the options given below:

• A. E, F, D, A, C and B
• B. B, F, D, A, C and E
• C. A, B, D, C, E, and F
• D. E, F, A, D, C and B

Hint:

Think of the logical path: a spore must first land on the leaf (Inoculation), get inside (Penetration), establish its nutrient supply (Infection), spread throughout the leaf (Invasion), multiply (Reproduction), and finally spread to other plants (Dissemination).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Pathogenesis is the chain of events that leads to disease development in a host plant.
It describes how a pathogen contacts, enters, colonizes, reproduces within, and spreads from a host.

Step 2: Detailed Explanation:
The logical chronological sequence of disease development consists of the following steps:
1. Inoculation (E): The first contact of the pathogen's propagule (inoculum) with the host plant.
2. Penetration (F): The physical entry of the pathogen into the host tissues, which can occur directly, through natural openings (stomata, hydathodes), or through wounds.
3. Infection (D): The establishment of a parasitic relationship between the pathogen and the host, where the pathogen starts deriving nutrients from the host cells.
4. Invasion (A): The colonization and spread of the pathogen through the tissues of the host.
5. Reproduction (C): The pathogen multiplies and produces new propagules (spores, cells) within or on the host tissue.
6. Dissemination (B): The newly produced propagules are released and spread by wind, water, insects, or other agents to infect new hosts.

Step 3: Final Answer:
The correct sequence is E (Inoculation) $\rightarrow$ F (Penetration) $\rightarrow$ D (Infection) $\rightarrow$ A (Invasion) $\rightarrow$ C (Reproduction) $\rightarrow$ B (Dissemination). This matches Option (A).