It is hard to predict how changes in the climate and the atmosphere’s chemistry will affect the prevalence and virulence of agricultural diseases. But there is a risk that such changes will make some plant infections more common in all climatic zones, perhaps catastrophically so. Part of the problem is that centuries of selective breeding have refined the genomes of most high-value crops. They are spectacular at growing in today’s conditions but genetic variations that are not immediately useful to them have been bred out. This is good for yields but bad for coping with changes. A minor disease or even an unknown one could suddenly rampage through a genetically honed crop.

Which one of the following statements best reflects the central idea conveyed by the passage?

Correct Option: Our total dependence on genetically honed crops entails possible food insecurity.

Explanation / Step-by-Step Breakdown:

1. Analyzing the Core Argument:
The passage starts by highlighting the risk that climate change and changes in atmospheric chemistry could make plant infections more widespread and potentially catastrophic. It then explains the underlying cause: centuries of selective breeding have created "genetically honed" crops. While these crops produce high yields in current conditions, they lack genetic diversity (variations not immediately useful were bred out).

2. Connecting the Cause and Risk:
Because high-value crops lack genetic diversity, they are vulnerable to unexpected disease outbreaks when environmental conditions change. A single new or minor disease could rampage through these crops, posing a grave threat to our food supply (food insecurity).

3. Evaluating the Options:
• Option 1: "Global climate change adversely affects the productivity of crops." — This is a background premise, not the main central idea focusing on genetic vulnerability.
• Option 2: "Our total dependence on genetically honed crops entails possible food insecurity." — This accurately synthesizes the main point: relying heavily on genetically uniform crops creates vulnerability to catastrophic disease outbreaks, risking food security.
• Option 3: "Our food security should not depend on agricultural productivity alone." — This misinterprets the text and introduces concepts not discussed.
• Option 4: "Genetically honed crops should be replaced with their wild varieties in our present cultivation practices." — The passage does not recommend completely replacing honed crops with wild varieties; it merely points out the trade-offs of selective breeding.

Thus, the statement that best reflects the central idea conveyed by the passage is "Our total dependence on genetically honed crops entails possible food insecurity."