Question

Which one of the following factors influences the determination of isolation distance requirements in cross-pollinated crops?

• A. Plant height
• B. Germination rate
• C. Soil fertility
• D. Type of pollinating agent

Hint:

To remember:
- Self-pollinated crops (e.g., Wheat, Rice) require very small isolation distances (typically only 3 meters) to prevent mechanical mixing during harvest.
- Cross-pollinated crops (e.g., Maize) require large isolation distances (up to 400--1,000 meters) to prevent pollen contamination.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
During certified seed production, seed crops must be physically separated from other fields of the same crop (or wild relatives) to prevent cross-pollination.
This separation is called the isolation distance and ensures the genetic purity of the harvested seed lot.

Step 3: Detailed Explanation:
The minimum isolation distance required for a crop is determined by its mode of pollination and the physical behavior of its pollen.
In cross-pollinated crops, the type of pollinating agent is the primary factor that determines this distance:
1. Wind-pollinated crops (Anemophilous): Pollen grains are lightweight and can travel long distances on wind currents (e.g., maize, pearl millet).
These crops require large isolation distances, often ranging from 200 to 1,000 meters or more, to prevent foreign pollen from drifting into the seed production field.
2. Insect-pollinated crops (Entomophilous): Pollen transfer depends on insects, such as bees, which fly within a limited foraging range (e.g., sunflower, cucurbits).
The isolation distance is designed based on the flight range and behavior of these insect vectors.
Let us evaluate the other options:
- Plant height (A), germination rate (B), and soil fertility (C) are agronomic and physiological characteristics.
They do not influence the distance that pollen can travel or the risk of cross-pollination.
Therefore, the type of pollinating agent is the key factor that determines isolation distance requirements.

Step 4: Final Answer:
The factor that determines isolation distance is the type of pollinating agent, matching Option (D).