Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Performance of synthetic varieties are better than single or double cross hybrids
Reason (R): Synthetics exploit only general combining ability (GCA) while hybrids exploit GCA and specific combining ability (SCA).

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Hybrids provide maximum yield potential, while synthetic varieties are advantageous because farmers can reuse their seeds for several generations.

Answer 1

The Correct Option is D

Concept: Synthetic varieties are developed by intercrossing several genotypes with good general combining ability (GCA), whereas hybrids are specifically produced to exploit heterosis.

Step 1: Examine the assertion.
Single cross and double cross hybrids generally outperform synthetic varieties because hybrids utilize maximum heterosis and hybrid vigor. Synthetic varieties are comparatively stable and economical but usually lower yielding than hybrids. Therefore, Assertion (A) is incorrect.

Step 2: Examine the reason.
Synthetic varieties mainly exploit additive gene action and general combining ability (GCA). In contrast, hybrids utilize both GCA and specific combining ability (SCA), which includes dominance and epistatic effects. Thus, the Reason (R) is scientifically correct.