Principles of Plant Breeding (2+1)

Phenotypic assortative mating

• Mating between individuals which are phenotypically more similar than would be expected under random mating.

  It leads to

  1. Division of the population into two extreme phenotypes. Intermediate types are not fixed. The highest and lowest remain in the population.
  2. Increase in homozygosity and genetic variability
  3. Prepotency increases.
• These effects disappear rapidly when random mating is restored. The effects of this mating are quick in the characters governed by single gene and goes on reducing as number of genes increased. For polygenic traits intermediate types are not eliminated. The effects are further reduced due to dominance and epistatic effects and for quantitative traits which have less than 100% heritability. So homozygosity is much lower.
• The mating system is useful in the isolating extreme phenotypes. It is used in some breeding scheme. E.g: Recurrent selection.