Question

Which of the following can result heterosis?

• A. Dominance
• B. Over dominance
• C. Epistasis
• D. More than one answer are correct

Hint:

In plant breeding, heterosis is the foundation of the commercial hybrid seed industry (e.g., hybrid maize, hybrid rice). The goal is to maximize these interactions for yield stability.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Heterosis, or hybrid vigor, refers to the phenomenon where the progeny (\(F_1\)) of two genetically diverse parents exhibit superior performance in traits like yield, growth rate, and stress tolerance compared to the average of the parents (mid-parent) or the better parent. Several genetic hypotheses have been proposed to explain this.

Step 2: Detailed Explanation:
The three primary genetic explanations for heterosis are:
1. Dominance Hypothesis: Suggested by Davenport (1908), it posits that heterosis results from the masking of deleterious recessive alleles from one parent by the dominant favorable alleles from the other parent in the hybrid.
2. Overdominance Hypothesis: Suggested by Shull and East (1908), it proposes that the heterozygous state (\(Aa\)) at certain loci is inherently superior to both homozygous states (\(AA\) or \(aa\)). This is sometimes called "heterozygote advantage."
3. Epistasis (Interaction) Hypothesis: This suggests that heterosis is caused by non-allelic interactions between genes at different loci. Complex interactions between genes can create synergistic effects that boost vigor in the hybrid.
Since modern genetic research shows that heterosis is a complex phenomenon often involving a combination of dominance, overdominance, and epistasis across various loci in the genome, all three mechanisms are scientifically valid contributors.

Step 3: Final Answer:
Dominance, Overdominance, and Epistasis are all established genetic mechanisms that result in heterosis. Thus, option 4 is correct.