What Is Inbreeding?

Inbreeding is a kind of close mating, which refers to the mating between close relatives such as parents, siblings, etc. Inbreeding is one of the important methods of breeding, maintaining and breeding excellent breeding stock and plant original species (including inbred lines).

Inbreeding

Close mating refers to mating between close relatives such as parents, siblings, etc. It is often used in breed improvement of livestock and poultry. Inbreeding is useful in maintaining good livestock breeds (such as Favourite

Mating between individuals with similar kinship is also called inbreeding, or inbreeding for short. It is a commonly used form of mating in animal and plant breeding and fine breed breeding. Extreme inbreeding is the self-pollination of plants self-pollinating. This is followed by full siblings of the same parental offspring, half siblings of the single parental offspring, and mating between ancestor offspring. Backcrossing between parents and offspring is also a form of inbreeding. The degree of inbreeding of a group or an individual depends on the degree of kinship between the parents or parents, and is usually measured by the inbreeding coefficient (F), that is, the probability that a gene from a common ancestor will meet in the offspring of inbreeding. The inbreeding coefficient varies between 0 and 1. In the animal husbandry, the total number of generations from the breeding parties to the common ancestor is within 6 generations, or the inbreeding coefficient of the offspring is greater than 0.78, which are all inbreeding.

Inbreeding can reduce the heterozygosity of the population, increase the homozygosity, and gradually stabilize the genetic traits. The rate of decrease in heterozygosity in each generation varies depending on the type of inbreeding: 1/2 for selfing, 1/4 for full siblings, 1/8 for half siblings, and 1/16 for siblings. Multiple generations of inbreeding in a population can make the population differentiate into multiple small groups composed of different genotypes, and lead to the gradual purification of each small group. Selection can maintain or continue to improve the degree of purification of each small group; if no selection is made, the variation of the small group will expand.

Although inbreeding can homozygous genes for dominant beneficial traits, it can also homozygous genes for recessive harmful traits. For example, "Kalakuur curl" type calf coats, a kind of congenital edema of calves, and a short-headed dwarf cattle are all caused by homozygous recessive genes. Therefore, inbreeding is often used to find and eliminate genes for recessive harmful traits in a population.

Normal inbreeding plants and animals often produce inbreeding decline when they are inbreeding, that is, inbreeding offsprings show viability, productivity, reproductive ability, stress resistance, decreased adaptability, and slow growth and development. The degree of inbreeding decline varies according to the type of strain. However, after successive generations of close relatives mate, the viability, adaptability, and yield of their offspring no longer continue to decrease. For example, for 20 consecutive generations of corn, the yield will stabilize and will not change. In production, measures to prevent and mitigate the decline of inbreeding include: reasonable selection of effective forms of inbreeding based on genetic principles and the requirements of commodity production; controlling the degree of inbreeding in groups; strengthening selection and elimination; and purposefully renewing kinship ; Improve feeding management or cultivation conditions.

Inbreeding is one of the important methods for breeding, maintaining and breeding good breeding stock and plant stocks (including inbred lines). In the breeding work of domestic animals, the family breeding and strain breeding methods have been adopted to relax the inbreeding methods, and many well-known excellent breeds of livestock have been cultivated, such as British shorthorn cattle, Leicester sheep, and China's Xinhuai pigs. For some crops, multiple generations of highly inbred methods are often used, combined with selection and breeding of inbred lines of different genotypes (including inbred lines), and selective mating to produce hybrids with strong heterosis. Application of this method to corn has significantly increased yield. In animal husbandry, high inbred lines can also be established through high inbreeding, and then economic hybridization between inbred lines can be implemented to produce commercial poultry. This method has been widely used in commercial production of chickens. However, due to the high economic cost of breeding inbred lines, it has not been widely popularized in livestock breeding. In medicine, breeding high-purity experimental animals (such as big and small mice), highly inbreeding is a common method. Many inbred lines will not show more abnormalities than normal lines once they are bred.