Question

The development of a synthetic variety in a cross-pollinated crop involves several activities that are performed serially one after another. Arrange the steps in chronological order i.e. from the beginning to the end:
(A). Production of the synthetic variety
(B). Collection of inbreds and testers (OPVs)
(C). Top cross or poly-cross test for GCA and selection of inbreds as parental lines
(D). Multilocation testing of the synthetic variety and distribution
Choose the correct answer from the options given below:

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

Hint:

In synthetic breeding, testing for General Combining Ability (GCA) is always done before the selected parental lines are mixed and intermated to produce the actual synthetic variety.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A synthetic variety is an open-pollinated variety developed by crossing a specific set of parental lines (such as inbred lines, clones, or open-pollinated varieties) that have been selected based on their general combining ability (GCA).
The development of a synthetic variety follows a structured breeding procedure.

Step 2: Detailed Explanation:
Let us trace the chronological steps of synthetic variety development:
1.

Step 1: Collection and Development of Parental Source Materials (B): The breeder first collects diverse inbred lines, clones, or open-pollinated varieties (OPVs) to serve as potential parents.
2. Testing for General Combining Ability (GCA) (C): To identify the best parents, these candidate lines are crossed with a common tester (top-cross) or allowed to cross-pollinate in a poly-cross design.
The resulting progeny are evaluated, and parents that show high GCA are selected to form the synthetic variety.
3.

Step 2: Production of the Synthetic Variety (Syn1 and Syn2) (A): The selected parental lines are crossed in all possible single-cross combinations.
The equal-quantity seeds of all possible \( F_1 \) crosses are mixed and allowed to intermate via open pollination. This produces the Syn1 generation, which is then grown to produce the Syn2 seed (commercial synthetic variety).
4.

Step 3: Evaluation and Release (D): The synthetic variety is evaluated in multi-locational trials against existing standard checks.
If it shows stable superior performance, it is officially released and distributed to farmers.
Thus, the correct chronological sequence of these breeding operations is (B) \( \rightarrow \) (C) \( \rightarrow \) (A) \( \rightarrow \) (D).

Step 3: Final Answer:
The correct chronological order of the steps is (B), (C), (A), (D), corresponding to option (B).