Concept: Heritability 0.2 and its implication

• Heritability h2=0.2h2=0.2 means only 20% of phenotypic variation is genetic; 80% is environmental.

• Individual plant phenotype is therefore a poor predictor of breeding value, so methods that average over progenies or families give more accurate selection.

Option-wise explanation

1. Pedigree selection

   • Relies heavily on individual plant phenotype plus recorded ancestry.

   • With low heritability, single-plant phenotype is unreliable, so pedigree selection is slow and less effective for quick gain.

2. Mass selection

   • Selects individual plants on phenotype and bulks their seed.

   • Works best when heritability is high; with h2=0.2h2=0.2, environmental noise makes it inefficient for rapid improvement.

3. Family selection

   • Uses performance of families (e.g., half-sib or full-sib) rather than individuals, which improves accuracy.

   • However, the classic, more rigorous version of this idea is progeny testing.

4. Progeny testing – correct

   • Plants are selected, their progenies grown and evaluated, and selection is based on progeny mean performance, which averages out environmental effects.

   • This is especially recommended for low-heritability traits, giving higher accuracy and better genetic gain in a relatively short number of generations.

Because the trait has low heritability (0.2) and rapid, reliable improvement is desired, progeny testing (option 4) is the most appropriate approach.