Principles of Genetics and Breeding

12.1.2 Use of inbreeding

Although inbreeding in general represents a harmful phenomenon, it can also be extremely useful in fish selection. This usefulness stems primarily from the stabilization of selection traits due to increased homozygosity and the augmented expression of several of them.

Inbreeding is a breeding programme that can be used

• to produce superior animal and plant brood stock,
• to produce genetically improved animals and plants for grow-out,
• to create new breeds or varieties that breed true for “type”; i.e., a particular body conformation or set of qualitative phenotypes.
• One of the major uses of inbreeding is line breeding.
• A major use of inbreeding is the creation of inbred lines that can be hybridized to produce F₁ hybrids for grow-out.
• Here, two or more selected lines are inbred to fix certain alleles.
• When the inbred lines are mated, the hybrids will be identical at the desired loci and will be uniform.
• Thus inbreeding in two or more lines followed by hybridization is the classic way of producing uniform progeny for grow-out.
• Though inbreeding depression is reported, sometimes outstanding inbred animals can be valuable as brood stock because they breed true for many phenotypes and will not perpetuate undesired phenotypes.