The genetic interpretation of inbreeding depression and outbreeding depression. All inbreeding does not result in disaster when the use of inbreeding centers on genetically superior individuals. Pdf inbreeding depression in the wild researchgate. We define inbreeding depression for some sire i to be the expectation of the phenotypic difference between outbred progeny io and inbred progeny if, or in terms of genetic effects, 2 since we are interested in the variation in the differential effects of inbreeding across breeding individuals, we define the variation in inbreeding depression effects ide, i. Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. Inbreeding depression, purging and genetic rescue are recognized as elements to be considered in conservation programs, and genomic monitoring of. Inbreeding depression has the greatest effect on reproductive traits, followed by growth traits, with little or no effect on carcass traits.
Hedrick1, 1school of life sciences, arizona state university, tempe, az 852874501, usa 2the living desert, palm desert, ca 922606156, usa 3turner endangered species fund, ladder ranch, caballo, nm 87931, usa although inbreeding can reduce individual. Nov 11, 2011 a significant positive relationship between parental genetic dissimilarity and the number of surviving offspring was observed, which indicated that inbreeding depression might have purged more inbred offspring. The genetic basis of inbreeding depression in potato nature. Fredrickson1, peter siminski2, melissa woolf 3 and philip w. When inbreeding depression is due to deleterious recessive alleles, the basic models predict that intermediate selfing rates are not evolutionarily stable and either. Published online20may2003 recent approaches into the genetic basis of inbreeding depression in plants david e.
Conversely, genetic load will be highest in species that have large population sizes and little inbreeding due to factors such as social organization which can subdivide. Inbreeding reduces phenotypic performance inbreeding depression and the genetic variation due to mendelian sampling among progeny of a particular set of parents. F is a very valuable parameter in both population and quantitative genetics. Nov 06, 2018 other traits in which inbreeding depression has been documented for beef cattle include percentage weaned, birth weight, preweaning gain, weaning weight, postweaning gain, and final weight. The effects of a bottleneck on inbreeding depression and the. Inbreeding depression the reduced survival and fertility of offspring of related individuals occurs in wild animal and plant populations as well as in humans, indicating that genetic variation in fitness traits exists in natural populations. We introduce an experimental design in which sires are mated to multiple dams, some of which are unrelated to the sire but others are genetically related owing. Other research proves that inbreeding is the major cause of mutations in the tiger population and hopefully further research will be done on other possible mutations that could occur within the species. Ppt inbreeding and inbreeding depression powerpoint.
Implications for protection and recovery of the genetic variation of extremely rare plants, such as o. As a clonally propagated crop, potato solanum tuberosum l. Inbreeding depression is often the result of a population bottleneck. Inbreeding depression is expected to play an important but complicated role in evolution. Genetic drift impacting small populations and inbreeding. Inbreeding is matting between individuals related by descent or ancestry. Where f x is the coefficient of inbreeding of individual x. Inbreeding depression resulting from partially recessive deleterious alleles is thought to be the main genetic factor preventing selffertilizing mutants from spreading in outcrossing hermaphroditic populations. The effects of a bottleneck on inbreeding depression and. Inbreeding depression the reduced survival and fertility of offspring of related individuals occurs in wild animal and plant populations as well as in humans, indicating that genetic variation. It can be seen that the issues of heterosis and inbreeding depression have a common biological aspect.
Today we will examine how inbreeding between close relatives also known as consanguineous matings influences the appearance of autosomal recessive traits. The genetic basis of inbreeding depression genetics. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. To understand the genetic basis of inbreeding depression and heterosis in rice, maineffect and epistatic qtl associated with inbreeding depression and heterosis for grain yield and biomass in. The cause of this depression is the load of deleterious recessive alleles that are. Following the rediscovery of mendelian genetics, two main hypotheses were formulated to account for the existence of inbreeding depression and heterosis gain in fitness following outbreeding. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity. Inbreeding depression in plants, caused by selfing or crossing among. Epistasis, inbreeding depression and the evolution of self.
Recent approaches into the genetic basis of inbreeding depression in plants. The genetic basis of inbreeding depression in potato. This result suggests that the genetic basis of inbreeding depression may differ among life stages. A genetic interpretation of the variation in inbreeding.
The biological fitness is an organisms ability to survive and conserve its genetic material. In brothersister mating or sib mating, the degree of inbreeding is high. Jan 23, 2020 inbreeding occurs when two closely related organisms mate with each other and produce offspring. Inbreeding depression is important in the evolution of outcrossing mating systems and, because intercrossing inbred strains improves yield heterosis, which is important in crop breeding, the genetic basis of these effects has been debated since the early twentieth century. Down, 17 july 1870 my dear lubbock, in england and many parts of europe the marriages of cousins are.
Key terms biodiversity, inbreeding, heterozygosity, homozygous, inbreeding depression, deleterious, mutation, phenotype, genetic. This pattern is the reverse of the magnitude of heritability for these classes of traits. The importance of distinguishing between the two main genetic consequences of small population sizesloss of genetic diversity and inbreeding depression. Accumulation of deleterious mutations due to inbreeding in.
Higher probability of inbreeding depression is expected when mating system shift from outcrossing or mixed mating to mainly selfing goodwillie et al. Researchers take first look at the genetic dynamics of. Pdf despite its practical application in conservation biology and evolutionary theory, the cost of inbreeding in natural populations of plants and. Bottlenecks reduce genetic variation genetic drift. Genetic decline and inbreeding depression in an extremely. The hybrid breakdown part of inbreeding depression values of individual rils were negatively associated with the heterosis measurements of their bc or testcross hybrids, indicating the partial genetic overlap of genes causing hybrid breakdown and heterosis in rice. The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Inbreeding and inbreeding depression 1 inbreeding and inbreeding depression 2 przewalskis horse 3 no transcript 4 ralls ballou 1983 5 back to inbreeding 6 chondrodystrophy in california condors q 0. In humans, its associated with consanguinity and incest, in which close relatives have sexual relationships and children. Inbreeding depression confers reduced fitness among the offspring of genetic relatives. Population biological fitness refers to an organisms ability to survive and perpetuate its genetic material. From the genealogists point of view the following are perhaps the two most interesting applications. Genetic basis of inbreeding depression in wiley online. Inbreeding depression ibd is the effect of inbreeding measured as the reduction in mean phenotypic performance with increasing levels of inbreeding within a population falconer and mackay, 1996.
Although inbreeding is a valuable breeding technique and one that can be combined with selection to improve response when h 2 is small or with crossbreeding to produce animals and plants that farmers grow for market, unplanned and uncontrolled inbreeding often leads to inbreeding depression. Although any of these genetic mechanisms could threaten population persistence, inbreeding poses the most immediate risk. Inbreeding depression in fitness components or fitnessrelated traits is a focus in assessing these costs. The house of habsburg may be the best example of the effects of inbreeding in humans. Inbreeding depression, the reduction of fitness caused by inbreeding, is a nearly universal phenomenon that depends on past mutation, selection, and genetic drift. Rare alleles are likely to be lost during a bottleneck two important determinants of the severity of a bottleneck are the duration and population size ne nonrandom mating inbreeding.
Traditionally, pedigreebased relationship coefficients have been used to manage the inbreeding and degree of inbreeding depression that exists within a population. Accumulation of deleterious mutations due to inbreeding in tiger population lauren begany c. Bottlenecks reduce genetic variation genetic drift northern elephant seals were reduced to 30 individuals in the 1800s. In spite of its prevalence, some researchers question whether inbreeding depression is important in wild populations, invoking two main arguments. Genetic parameters, inbreeding depression and genetic trends were estimated for average daily gain between the ages of 510 weeks and thigh muscle volume measured in vivo with computerized tomography in a group of 22098 pannon terminal line rabbits born between 2006 and 2011 and reared in 3 396 litters. Genetic rescue and inbreeding depression in mexican wolves richard j. However, deleterious alleles may also generate an advantage to selfers in terms of more efficient purging, while the effects of epistasis among those alleles on inbreeding depression. While linebreeding is less likely to cause problems in the first generation than does inbreeding, over time, linebreeding can reduce the genetic diversity of a population and cause problems related to a toosmall gene pool that may include an increased prevalence of genetic disorders and inbreeding depression. Inbreeding violates modern social norms, but is fairly common in animals and plants.
Genetic parameters, genetic trends and inbreeding depression. Understanding inbreeding depression, purging, and genetic. To gain insight into inbreeding depression in potato. Genetic basis of heterosis and inbreeding depression in. Inbreeding depression plays a significant role in crop breeding and in the evolution of outcrossing mating systems. Genetic basis of heterosis and inbreeding depression in rice. Abstract biodiversity in a species is the amount of genetic variability within the species. The genetic basis of heterosis was studied through midparent, standard variety and better parent for 11 quantitative traits in 17 parental lines and their 10 selected hybrids in rice oryza sativa l. Genetic diversity refers to the total number of genetic characteristics in the genetic. Inbreedingwith close relatives and outbreeding with members ofdistant populations can both result in deleterious shifts in the means offitnessrelatedcharacters, mostlikely for very. Inbreeding depression can reduce the performance of the progeny with consequences for populations and species persistence.
Inbreeding and inbreeding depression inbreeding is mating among relatives which increases homozygosity why is inbreeding a conservation concern. Inbreeding depression as a measure of the cost of selffertilization slides 911. The genetic interpretation of inbreeding depression and outbreeding depression michael lynch department ofbiology, university oforegon, eugene, or 97403 usa abstract. The functional genomics of inbreeding depression oxford. Genetic interpretation of inbreeding and outbreeding 623 this paper is an attempt to put the con cepts of inbreeding depression, outbreeding enhancement, and outbreeding depression in a unifying framework and to provide a methodological basis for evaluating the ge netic bases of these phenomena. Inbreeding depression and outbreeding depression metapedia.
The primary selfing rate of the tetraploid population was r 0. The widespread incorporation of genomic information in dairy cattle genetic evaluations allows for the opportunity to develop and implement. Lecture 27 effects of inbreeding mit opencourseware. Genetic parameters, inbreeding depression and genetic trends were estimated for average daily gain between the ages of 510 weeks and thigh muscle volume measured in vivo with computerized tomography in a group of 22098 pannon terminal line rabbits born. Introduction about inbreeding depression, effect and degrees of inbreeding depression. Inbreeding may or may not lead to inbreeding depression, which is a reduction in the fitness in the offspring produced by inbred matings. Measures of inbreeding inbreeding coeffi cients represent the homozygosity expected in an animals genome because of the relatedness of its parents. The major hurdle that must be overcome in the development of new inbred strains from wild populations is inbreeding depression which occurs most strongly between the f 2 and f 8 generations second through eighth generation of sequential brothersister mating. Dudash2 1blandy experimental farm, university of virginia, 400 blandy farm lane, boyce, va 22620, usa.
This phenomenon is well documented in all the major livestock species. The genetic basis of reduced inbreeding depression in. Two identical alleles at the same locus can in some cases be the alternative with the highest fitness homozygote advantageunderdominance. Loss of genetic diversity and inbreeding in new zealands. Inbreeding is a fundamental genetic tool applied to the laboratory mouse and detailed information is available on the web table 3. The two main negative consequences of inbreeding are an increased risk of undesirable genes and a reduction in genetic diversity. Calculation and use of inbreeding coefficients for genetic. The genetic basis of reduced inbreeding depression in polyploids introduction inbreeding depression is the reduced fitness of inbred offspring relative to outbred offspring. A significant positive relationship between parental genetic dissimilarity and the number of surviving offspring was observed, which indicated that inbreeding depression might have purged more inbred offspring. The genetic interpretation of inbreeding depression and. Note that inbreeding will not make a difference for dominant traits because they need. Pdf overdominant epistatic loci are the primary genetic. Based on recent studies in many species, the authors argue that both.
Genetic rescue and inbreeding depression in mexican wolves. If we are to understand the evolution of inbreeding depression i. Recent approaches into the genetic basis of inbreeding. Pdf the genetics of inbreeding depression researchgate. Inbreeding depression an overview sciencedirect topics. There are several genetic mechanisms which may cause outbreeding depression. Deleterious mutations probably play a major role in causing inbreeding depression. Overdominant epistatic loci are the primary genetic basis of. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Understanding inbreeding depression, purging, and genetic rescue. The widespread incorporation of genomic information in dairy cattle genetic evaluations allows for the opportunity to develop and implement methods to manage populations at the.
Inbreeding depression in plant breeding biotech articles. Classical genetic studies and modern molecular evolutionary approaches now suggest that inbreeding depression and heterosis are. Jul 01, 2005 inbreeding depression is expected to play an important but complicated role in evolution. Genetic interpretation of inbreeding and outbreeding 623 this paper is an attempt to put the con cepts of inbreeding depression, outbreeding enhancement, and outbreeding depression in a unifying framework and to provide a methodological basis for evaluating the ge. Heterosis and inbreeding depression in f2 populations of. Jan 14, 2019 inbreeding depression confers reduced fitness among the offspring of genetic relatives. Breeding material used during the study of genetic potential, heterotic effects and inbreeding depression for yield related traits in 6. Little in 1909, with the subsequent creation of over inbred strains and stocks of mice festing, 1996. Researchers take first look at the genetic dynamics of inbreeding depression 12 march 2009 declines in reproductive success due to inbreeding are. To understand the genetic basis of inbreeding depression and heterosis in rice, maineffect and epistatic qtl associated with inbreeding depression and heterosis for grain yield and biomass in five related rice mapping populations were investigated. Hedrick1, 1school of life sciences, arizona state university, tempe, az 852874501, usa. The level of inbreeding depression has been suggested to determine a plants mating.
633 1026 941 1535 525 294 1202 321 499 1391 447 441 1095 491 871 148 55 269 239 140 439 199 670 1496 1232 1443 1315 1379