What does it tell you when a non-wounded inoculated fruit did not produce any symptoms whereas, wounded inoculated fruit became infected?

Question

BlackTom AI · Accepted Answer

The fruit cuticle is a physical barrier that prevents pathogen entry, so when only wounded inoculations produce disease it indicates that intact epidermal/cuticular layers blocked infection.

Relevant concepts:
- Plant cuticle/epidermis: a continuous hydrophobic layer that prevents direct penetration by many microbes.
- Pathogen entry: many pathogens require natural openings, wounds, or enzymatic penetration to access internal tissues.
- Virulence vs. entry limitation: A pathogen can be virulent (able to cause disease) but still unable to infect if it cannot gain entry.
- Quiescent infection: pathogen enters or persists without symptoms (latent), often detectable later or under conducive conditions.

Step-by-step reasoning:
1. Two treatments were compared: inoculation onto non-wounded fruit and inoculation onto wounded fruit.
2. Observation: non-wounded inoculated fruit showed no symptoms; wounded inoculated fruit became infected and showed disease.
3. If the pathogen were not virulent (choice A), it would fail to cause disease even when given direct access. But because wounded fruit became diseased, the pathogen clearly can cause infection when it gains access; therefore A is false.
4. If the situation were quiescent infection (choice C), we would expect the pathogen to be present inside intact tissue without symptoms. However, quiescence implies the pathogen has already entered or established latent infection in non-wounded tissue; the fact that non-wounded fruit showed no infection while wounded fruit developed symptoms indicates the limiting factor is entry, not dormancy. Also, quiescent pathogens often can be recovered from non-symptomatic tissue; that was not reported.
5. The simplest and best-supported explanation is that the intact cuticle prevented pathogen entry, and wounding bypassed that barrier, allowing infection.

Why the correct answer is correct:
- The pattern (disease only after wounding) matches an entry-limited infection where the cuticle is the barrier. Wounding provides a breach, enabling pathogen access and disease.

Why the other options are incorrect:
- "A: The pathogen is not virulent" is contradicted by infection of wounded fruit.
- "C: The infection must be quiescent" is not supported because quiescence implies internal establishment without symptoms; here infection only occurs when the barrier is removed.
- Options combining A with others are therefore also incorrect.

Conclusion: The correct answer is B: The cuticle of the fruit is a barrier to infection. This matches the provided answer.

What does it tell you when a non-wounded inoculated fruit did not produce any symptoms whereas, wounded inoculated fruit became infected?单项选择题

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