Arguments against intermating before selection in a self-fertilising species

Area of Science:

• Quantitative Genetics
• Plant Breeding
• Population Genetics

Background:

• Intermating F2 populations is a strategy to increase homozygosity and genetic gain.
• Understanding the conditions under which intermating is most beneficial is crucial for breeding programs.

Purpose of the Study:

• To investigate the expected benefits of intermating F2 populations derived from crosses of two homozygous parents.
• To evaluate the impact of allelic phase and recombination frequency on the efficacy of intermating.

Main Methods:

• Population simulation was used to extend findings from two loci to multiple loci.
• The merit of intermating was quantified by the ratio of population variance after one cycle of intermating and selfing (V1) to the initial variance (V0).

Main Results:

• Intermating provides benefits primarily when alleles are in the repulsion phase.
• The gain from intermating decreases as recombination frequency increases, becoming consistently small when loci are spread across multiple chromosomes.
• Simulation studies demonstrated that truncation selection is generally more effective than intermating for increasing desirable homozygotes.

Conclusions:

• The effectiveness of intermating is highly dependent on the initial allelic phase and the genetic architecture of the trait.
• For most scenarios, particularly with higher recombination rates or loci on different chromosomes, truncation selection is a more efficient breeding strategy.