Question

Which of the following annuals require the isolation distance of 50-100 meters for seed production?
(A). Antirrhinum
(B). Marigold
(C). Larkspur
(D). Nasturtium
Choose the correct answer from the options given below:

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

Hint:

Self-pollinated or partially cross-pollinated flower crops like Antirrhinum, Sweet Pea, and Nasturtium require lower isolation distances (50-100 m), while highly cross-pollinated Asteraceae crops like Marigold and Zinnia require up to 400 m.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
To maintain genetic purity in seed production of flowering crops, cross-pollination must be restricted.
This is achieved by maintaining a minimum physical isolation distance between different varieties of the same species during cultivation.

Step 2: Detailed Explanation:
- Antirrhinum (Antirrhinum majus): Primarily self-pollinated but experiences considerable cross-pollination by insects.
According to minimum seed certification standards, it requires an isolation distance of 50 to 100 meters (depending on whether it is foundation or certified seed class) to prevent varietal contamination.
- Nasturtium (Tropaeolum majus): Possesses large flowers that attract insect pollinators, requiring a safe isolation distance of 50 to 100 meters to prevent genetic mixing.
- Marigold (Tagetes species): Is a highly cross-pollinated crop due to protandry and active insect visitation.
It requires much larger isolation distances (typically 200 to 400 meters) to produce genetically pure seeds.
Hence, Antirrhinum and Nasturtium are the annuals with an isolation distance requirement in the 50-100 meter range.

Step 3: Final Answer:
The annuals requiring an isolation distance of 50-100 meters are Antirrhinum and Nasturtium.