Question

The steps involved in the utilization of hybrid vigor in maize include-
A. Production of suitable inbred lines
B. Crossing of the selected inbreds in suitable combinations to produce highly productive single cross hybrids
C. Mixing of different single cross hybrid seeds to produce productive double cross hybrids
D. Crossing of the single cross hybrids in suitable combinations to produce highly productive double cross hybrids
Choose the correct answer from the options given below:

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

Hint:

To produce a double-cross hybrid, you must physically cross the single-cross hybrids ($AB \times CD$), not just mix their seeds. Mixing seeds is a mechanical action, whereas crossing is a genetic hybridization process.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Hybrid vigor (heterosis) in maize is utilized by crossing distinct, homozygous inbred lines.
To produce commercial double-cross hybrids (the classical method developed by D.F. Jones), a systematic, two-generation crossing scheme is required.

Step 2: Detailed Explanation:
Let us analyze the steps involved in hybrid maize seed production:
Step A: Production of suitable inbred lines: Homozygous, uniform inbred lines are developed through continuous self-pollination (selfing) for 5 to 7 generations. This is the foundation of hybrid breeding. Thus, A is correct.
Step B: Production of single-cross hybrids: Two selected inbred lines are crossed (e.g., $A \times B \rightarrow AB$, and $C \times D \rightarrow CD$) to produce highly productive single-cross hybrids. Thus, B is correct.
Step D: Production of double-cross hybrids: To overcome the low seed yield of inbred parents, two different single-cross hybrids are crossed in the field (e.g., $AB \times CD \rightarrow ABCD$). This produces the commercial double-cross hybrid seed. Thus, D is correct.
Step C: Mixing of different single-cross seeds: Physically mixing single-cross seeds would only result in a physical mixture of two single crosses, which would show genetic segregation, uneven heights, and poor yield. It does not produce a double-cross hybrid. Thus, C is incorrect.

Step 3: Final Answer:
The correct steps are A, B, and D only.
Therefore, the correct option is (A).