Symposium review: Breeding a better cow-Will she be adaptable?

Area of Science:

• Quantitative genetics and evolutionary biology.
• Animal and plant breeding.
• Genomic selection and genome editing.

Background:

• Adaptation to environments requires sufficient genetic variation.
• Evolutionary forces like drift, mutation, recombination, selection, and migration influence genetic variation.
• The infinitesimal model, commonly used in genetic evaluations, assumes numerous loci with small effects, implying selection minimally alters allele frequencies after initial generations.

Purpose of the Study:

• To evaluate the role of genetic variation in adaptation.
• To assess the impact of selection on genetic variability over time.
• To determine if genetic variation is a limiting factor for adaptation in breeding programs.

Main Methods:

• Review of theoretical models of quantitative genetics, including the infinitesimal model.
• Analysis of empirical evidence from long-term selection experiments in various species (e.g., corn, dairy cattle).
• Consideration of the utility of heritability versus coefficient of genetic variation for assessing adaptation potential.

Main Results:

• Long-term selection does not necessarily deplete genetic variation; empirical studies show sustained response to selection.
• The coefficient of genetic variation is a more informative metric than heritability for gauging adaptation potential.
• Observed rapid responses to reverse selection in long-term studies indicate remaining genetic variance.

Conclusions:

• There is ample genetic variability to support adaptation in populations, including dairy cattle breeding programs.
• New technologies like genome-wide selection and genome editing may enhance or preserve genetic variation.
• Concerns about a lack of genetic variability limiting adaptation are not supported by current evidence.