Question

Nucleus seeds maintain the highest genetic purity. In carrots, which one of the following methods is used to produce the nucleus seeds?

• A. Seed-to-seed method
• B. Root-to-seed method
• C. Stump-to-seed method
• D. Bud-to-seed method

Hint:

For any root crop (carrot, radish, turnip), producing nucleus/breeder seed requires the root-to-seed method.
This is because direct visual inspection and roguing of the underground roots are necessary to maintain genetic purity.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Nucleus seed is the initial, highly purified seed produced under the direct supervision of a plant breeder, serving as the source for breeder seed.
For root crops like carrots (Daucus carota), the selection of parental roots based on phenotypic characteristics (color, shape, core size, and lack of splitting) is essential to maintain genetic purity and prevent varietal drift.

Step 2: Detailed Explanation:
There are two primary methods used for seed production in biennial root crops:
1. Seed-to-seed method (A): In this method, seeds are sown, and the plants are left in the same field to overwinter, flower, and produce seeds the following year without transplanting.
While this method is less labor-intensive and yields more seed, it does not allow for the inspection or selection of the underground roots.
Thus, it cannot be used for producing high-purity nucleus or breeder seeds, as off-type roots cannot be rogued out.
2. Root-to-seed method (B): In this method, carrots are grown to the fully mature root stage.
The roots are carefully harvested, washed, and examined.
Any root displaying undesirable traits (such as poor core color, green shoulders, branching, or off-shapes) is discarded (rogued).
The selected, high-quality roots are then root-trimmed, top-pruned (leaving a short stump), and transplanted into a well-isolated field to produce the seed crop.
This rigorous physical selection makes the root-to-seed method the standard procedure for producing high-purity nucleus and breeder seeds in carrots.
3. Stump-to-seed method (C): This is a variation of the root-to-seed method used primarily for cabbage (where the head is cut, leaving a stump) rather than carrots.

Step 3: Final Answer:
The root-to-seed method is used to produce nucleus seeds in carrots, which corresponds to option (B).