Heterosis breeding and inbreeding depression authorstream. Heterosis and inbreeding depression of epigenetic arabidopsis. H is greatest when alleles are fixed in one population and. Based on recent studies in many species, the authors argue that both. Three levels of crosses selfing and withinpopulation and between population crosses were carried out and phenotypic values of the progeny were analyzed to assess individual inbreeding depression and between population heterosis or outbreeding depression. Heterosis, otherwise known as outbreeding enhancement, is the opposite of inbreeding depression and is sometimes referred to as hybrid vigor. Inbreeding depression and heterosis arise from the effects of gene combinations, that is, the effects of pairs of genes. In this article we will discuss about heterosis or hybrid vigour. Mar 29, 2016 genetical and physiological basis of heterosis and inbreeding 1. Decoupling the variances of heterosis and inbreeding.
Heterosis and inbreeding depression in two soybean single crosses. The different sources of variation in inbreeding depression. Winn1 1department of biological science, florida state university, tallahassee, fl 323064295, usa. Expected means and variances among inbred lines and their crosses c. Jun 04, 2017 the key difference between heterosis and inbreeding depression is that heterosis is the enhancement of traits due to the mixing of genes from two different individuals during outbreeding while inbreeding depression is the reduced biological fitness of offspring due to the increased homozygosity as a result of inbreeding between closely related. Heterosis or hybrid vigor is a phenomenon in which the f1 progeny is superior in characteristics than its inbred parents. We will be analyzing nine phenotypic traits to help us determine if there is a significant difference between the diploid and triploid hybrid plants in heterosis as well as diploid and tetraploid hybrid plants for the rate of inbreeding depression. Breeding techniques of crops and organisms have evolved over the past centuries. Pdf difference between inbreeding and interbreeding. Difference between heterosis and hybrid vigour compare the. Heterosis and inbreeding depression cross pollinated species and species reproducing asexually are highly heterozygous. Inbreeding may or may not lead to inbreeding depression, which is a reduction in the fitness in. Overdominant epistatic loci are the primary genetic basis.
Decoupling the variances of heterosis and inbreeding effects. Genetic basis of heterosis and inbreeding depression in rice. Nov 01, 2008 inbreeding depression, heterosis, and outbreeding depression simultaneously occur in the f 1 of a structured population. However, outcrossing can reduce mean population fitness if hybridization disrupts coadapted gene complexes or favorable epistatic interactions. Pdf inbreeding depression and its evolutionary consequences. Inbreeding may or may not lead to inbreeding depression, which is a reduction in the fitness in the offspring produced by inbred matings.
In the particular biallelic model, this depression is written. Depresi bawaan adalah fenomena yang menggambarkan penurunan tingkat kebugaran biologis pada hibrida offsprings karena perkawinan sedarah. There is also a difference between the terminology of the two terms hybrid vigour and heterosis as described by whaley in 1944. The main difference between inbreeding and interbreeding is that inbreeding is a breeding of genetically similar parents whereas interbreeding is a breeding between. Heterosis hybrid vigor and inbreeding depression, commonly considered as corollary phenomena, could nevertheless be decoupled under certain assumptions according to theoretical population genetics works. 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. H is proportional to the square of the difference in gene frequency between populations. Study of heterosis and inbreeding depression under natural and water stress conditions in diverse maize hybrids. Inbreeding has a strong effect on overall green matter yield in spaced plants. Inbreeding depression and heterosis in most populations of animals, or higher plants, mobility is restricted. Thus, heterosis in breed crosses involving bos taurus breeds can likely be accounted for by recovery of accumu lated inbreeding depression that has occurred in breeds since their formation.
Backcross, heterozygosity, homozygosity, hybrid, inbreeding, inbreeding depression, mating, outbreeding, selfbreeding. Department of plant biology, michigan state university, east lansing, mi 4882412, usa. The main difference between inbreeding and interbreeding is that inbreeding is a breeding of genetically similar parents whereas interbreeding is a breeding between two different species the same. Department of plant biology, michigan state university, east lansing, mi. Inbreeding depression, heterosis, and outbreeding depression simultaneously occur in the f 1 of a structured population. Inbreeding and inbreeding depression inbreeding is mating among relatives which increases homozygosity why is inbreeding a conservation concern. Inbreeding depression refers to the decrease or loss of fitness and strength which is mainly caused due to inbreeding.
Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield andor some other characters. Inbreeding depression is often the result of a population bottleneck. It results in a decline in survival and reproduction reproductive fitness, known as inbreeding depression, in most species of. Genetic basis of heterosis and inbreeding depression in. To explore this issue on real data, we analyzed the components of genetic variation in a population derived from a halfdiallel cross between. Inbreeding depression refers to the reduced vigor in the offspring from matings involving related parents. Population biological fitness refers to an organisms ability to survive and perpetuate its genetic material. Heterosis vs inbreeding depression heterosis adalah fenomena yang meningkatkan sifat pada hibrida daripada pada orang tua mereka karena pencampuran genom atau perkawinan sedarah.
As with inbreeding depression, directional dominance is required for heterosis. The inbreeding depression depends on the dominance, and on the inbreeding level. Heterosis is often discussed as the opposite of inbreeding depression although differences in these two concepts can be seen in evolutionary considerations such as the role of genetic variation or the effects of genetic drift in small populations on these concepts. Comparisons with multilocus, individualbased simulations show that these analytical approximations are accurate as long as the effects of interference stay moderate, but fail for high deleterious mutation rates and low. What are the similarities between inbreeding and outbreeding outline of common features 4. As biotechnology developed rapidly, modern techniques of breeding with the modern terminology related to them were introduced to identify these breeding methods. Our results show that within a metapopulation, inbreeding depression, heterosis, and outbreeding depression are simultaneously expressed on different traits. H is greatest when alleles are fixed in one population and lost in the other so. Inbreeding depression an overview sciencedirect topics. Inbreeding it is mating between individuals related by descent or. On the basis of his experiments beal 18771882 concluded that f 1 hybrids yield as much as 40 percent more of the parental varieties from subsequent studies on intervarietal crosses in maize, it was observed that some of the hybrids show heterosis. Effects of interference between selected loci on the.
In this study we manipulated the relatedness among parental individuals, from selfing to interpopulation outcrossing, as well as the direction of hybridization e. Pdf study of heterosis and inbreeding depression under. Shull 1952 coined the term heterosis and defined it as. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. An investigation on heterosis and inbreeding depression in. The relationships among these concepts is presented diagrammatically in fig.
What is the difference between inbreeding and outbreeding comparison of key differences. Between this depression and the inbreeding coefficient f, the relation is linear as long as it. Oct 23, 2017 key difference heterosis vs hybrid vigour. Ag84te composite breeds to use united states department. H is proportional to the square of the difference in allele frequencies between populations. Inbreeding depression and low betweenpopulation heterosis.
However, one must understand the differences between the types and frequencies of genetic variants that may cause inbreeding depression and heterosis summarized in table 2 and in the main text. Cross pollinated species and species reproducing asexually are highly heterozygous. Inbreeding in animals and plants leads to the formation of weak and lowfertile offspring inbreeding depression. Mechanisms of inbreeding depression and heterosis for. What is the difference between heterosis and inbreeding. Inbreeding it is mating between individuals related by descent or having common ancestry.
Maize was planted in completely randomized blocks replicated three times. Inbreeding depression loss or decrease in vigor due to inbreeding. Edwards heterosis is the foundation of modern maize breeding programs. An additive gene expression level is characterized by a nonsignificant difference between the f1 and the midparent value but a significant difference between the f1 and the two parents. Consequently, mating between individuals of such populations is far from random, this being affected among individuals occurring in proximity with each other in space. Difference between heterosis and inbreeding depression. Heterosis and inbreeding depression kana ram kumawat, ravi kumawat and madhu choudhary. Heterosis and inbreeding depression of epigenetic arabidopsis hybrids. In contrast, inbreeding depression consists of detrimental reductions of phenotypic trait values in the offspring of genetically related parents. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of. In simpler form, the mating between the relatives in a small population is common and this may lower the populations ability to persist and reproduce which is referred to as inbreeding depression. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. Feb 07, 2014 the effect of inbreeding rate on fitness, inbreeding depression and heterosis over a range of inbreeding coefficients nina pekkala, 1 k emily knott, 1 janne s kotiaho, 1, 2 kari nissinen, 3 and mikael puurtinen 1, 4.
Heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of development, and fertility than both parents. Mechanisms of inbreeding depression and heterosis for profitable dairying bennet cassell extension dairy scientist, genetics and management virginia polytechnic institute and state university, blacksburg genes in diploid organisms operate singly, in pairs, and in conjunction with genes at other locations throughout the nuclear dna. Specific crossbred combinations originate maximum utilization of heterosis and of breed differences in maternal and paternal performance. Inbreeding depression is normally reduced by immigrants that are heterozygous for deleterious recessive mutations whitlock et al. In subdivided populations, interference increases inbreeding depression within demes, but decreases heterosis between demes. The effect of inbreeding rate on fitness, inbreeding. Based on degree of depression, the plant species can be grouped into four broad categories. Effects of population size and isolation on heterosis. A phenotypic comparison of heterosis and inbreeding.
Effects of population size and isolation on heterosis, mean. The objectives of the research reported here were 1 to estimate heterosis and inbreeding depression in populations derived from crosses between modern cultivars that would be typical of a standard pedigree selection program, and 2 to compare the results with those obtained by brim and. Heterosis and inbreeding depression in two soybean single. High inbreeding depression inbreeding leads to severe depression and exhibit lethal effects. The key difference between heterosis and inbreeding depression is that heterosis is the enhancement of traits due to the mixing of genes from two different individuals during outbreeding while inbreeding depression is the reduced biological fitness of offspring due to the increased homozygosity as a result of inbreeding between closely related individuals. The contribution of epigenetic factors to inbreeding depression and heterosis remains elusive. Degrees of inbreeding depression various plant species exhibit different degrees of inbreeding depression. Heterosis and inbreeding depression biotech articles. Difference between inbreeding and outbreeding compare. Genetical and physiological basis of heterosis and inbreeding. The main difference between heterosis and inbreeding depression is that heterosis consists of beneficial augmentations of phenotypic trait values in offspring of genetically distant parents.
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. When two homozygous inbreeds a true breeding line obtained by continuous inbreeding of genetically unlike constituents are crossed together, the resulting hybrids obtained from. Understanding how parental distance affects offspring fitness, i. Genetic basis of inbreeding depression and heterosis. Now epigenetic arabidopsis hybrids show that epigenetic diversity and regulation contribute to both. Two of them, proposed within the first decade after rediscovery of mendels work, claimed wide acceptance. Genetical and physiological basis of heterosis and inbreeding dev hingra ph. The key difference between inbreeding and outbreeding is that inbreeding is a process of mating or breeding genetically close relatives for 4 to 6 generations while outbreeding is a process of mating distantly related or unrelated individuals over 4 to 6 generations.
Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield and or some other characters. Introduction diversity among breeds of bombyx mori causes the opportunity to increase cocoon production efficiency through crossbreeding. Darwin 1876 also reported that inbreeding in plants results in deterioration of vigour and the crossing in hybrid vigour. It is more appropriate to term the developed superiority of the hybrids as hybrid vigour whereas heterosis can be used to describe the mechanism by which superiority is developed. While inbreeding is often associated with fitness reduction inbreeding depression, interpopulation outcrossing may have either positive heterosis or negative outbreeding depression. Genetic basis of inbreeding depression and heterosis several hypothesis were put forward to explain inbreeding depression and conversely to explain the related phenomenon of hybrid vigour. The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Hybrid vigor is the opposite of inbreeding depression and is described as the masking of recessives through crossing of unrelated genotypes. Difference between heterosis and hybrid vigour compare. Inbreeding refers to mating of related individuals. Heterosis, inbreeding depression, various theories of. Two of them, proposed within the first decade after. Despite its importance in maize production, we know surprisingly little about the genetic basis of heterosis.
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