The level of heterosis in f 1 and f2generations along with inbreeding depression for all the crosses are presented in table 1. Darwin 1876 also reported that inbreeding in plants results in deterioration of vigour and the crossing in hybrid vigour. Whereas due to heterosis the hybrids are known to exhibit a greater resistance to insects or diseases than the parents. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of dollars of sales and investments in.
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. After maize hybrid was first utilized in field on a large scale in usa in 1930s, heterosis of other crops such as rice, sorghum, rape, and vegetable etc began to be widely used in production, and had made great achievements in crop breeding by the end of last century, mainly contributed to notable increasing of crop yield. The genetic interpretation of inbreeding depression and. Inbreeding depression, inbreeding depression and heterosis, genetics. The contribution of epigenetic factors to inbreeding depression and heterosis remains elusive. The genetic basis of reduced inbreeding depression in. The selfpollinated crops do not show inbreeding depression. Inbreeding depression and heterosis arise from the effects of gene combinations, that is, the effects of pairs of genes. Based on degree of depression, the plant species can be grouped into four broad categories. Ppt heterosis powerpoint presentation free to view id. Inbreeding depression and heterosis of hybrids in f2 populations of maize in the sao paulo state, brazil. All structured data from the file and property namespaces is available under the creative commons cc0 license.
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 an overview sciencedirect topics. The level of inbreeding depression has been suggested to determine a plants mating. Mar 12, 2017 know about inbreeding and inbreeding depression, along with the degrees of depression. Inbreeding depression it refers to decrease in fitness and vigour due to inbreeding. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield and or some other characters. 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. Department of plant biology, michigan state university, east lansing, mi 4882412, usa.
Inbreeding depression is often the result of a population bottleneck. 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. In a small population, matings between relatives are common. The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Two of them, proposed within the first decade after rediscovery of mendels work, claimed wide acceptance. Heterosis breeding in eggplant solanum melongena l. Allelic and nonallelic interactions of genes in presence of specific environmental effects will lead us to successful heterosis results. Heterosis is often discussed as the opposite of inbreeding depression.
An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. Heterosis and inbreeding depression by shreyartha mukherjee a dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of doctor of philosophy major. 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. Available formats pdf please select a format to send. Heterosis seems to be mainly produced by the presence of com plementary sets of deleterious recessive alleles within both parental populations and the masking. Heterosis and inbreeding depression kana ram kumawat, ravi kumawat and madhu choudhary department of plant breeding and genetics, s. Wgree files so that the foreign ancestors would be known. This study aimed to evaluate the agronomic traits of hybrids in f 2 populations, estimate of heterosis in relation to the average of the parents and determine the inbreeding depression in f 2 parents populations.
Inbreeding depression is normally reduced by immigrants that are heterozygous for deleterious recessive mutations whitlock et al. 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. Effects of interference between selected loci on the. Now epigenetic arabidopsis hybrids show that epigenetic diversity and. Genetic basis of heterosis and inbreeding depression in. Shell weight showed low level of heterosis in f1 hybrids 14 to 20 %, whereas the effect of inbreeding depression in f2 progeny was 4.
The converse or complement to inbreeding depression in which the value d a inbreeding can result in loss of vigor, size, etc. Heterosis breeding and inbreeding depression authorstream. Inbreeding depression definition of inbreeding depression. This inbreeding may lower the populations ability to survive and reproduce, a phenomenon called inbreeding depression. Inbreeding depression and heterosis in most populations of animals, or higher plants, mobility is restricted. Roze and rousset 2004 the mutation load, inbreeding depression, and heterosis generated by a single deleterious allele in a subdivided population with random mating within demes are approximately 16 17 18 where p is the frequency of the deleterious allele in the whole. Learn inbreeding depression with free interactive flashcards. What links here related changes upload file special pages permanent link. Combining ability, heterosis and inbreeding depression. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. The degree of inbreeding is measured by inbreeding.
Heterosis refers to the phenomenon that progeny of diverse varieties of. Hybrid vigor in plants and its relationship to insect pollination pdf. High inbreeding depression inbreeding leads to severe depression and exhibit lethal effects. After 3 or 4 generations of selfing it is hard to maintain lines. Presentations ppt, key, pdf logging in or signing up. The explanation for inbreeding depression lies in the evolutionary history of the population. Inbreeding depression refers to the reduced vigor in the offspring from matings involving related parents. The decline in size and vigour due to inbreeding is illustrated in figure 47. Know about inbreeding and inbreeding depression, along with the degrees of depression. Genetical and physiological basis of heterosis and inbreeding slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The genetic basis of reduced inbreeding depression in polyploids. Inbreeding depression and its evolutionary consequences. Inbreeding depression and drift load in small populations. Ppt heterosis powerpoint presentation free to view.
Inbreeding depression and drift load in small populations at demographic disequilibrium rachel b. Agriculture university jobner303329, jaipur, rajasthan, india email. Inbreeding depression is the loss of viability or function resulting from excess inbreeding, as noted in many populations including plant, dog and human where the negative consequences of inbreeding have been most commonly noted. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of. Effects of population size and isolation on heterosis. Inbreeding depression results due to fixation of unfavourable recessive genes in f2 fitness and vigour relationship. Accounting for inbreeding and crossbreeding in genetic. Inbreeding depression, genetic load, and the evolution of. Heterosis and outbreeding depression in crosses between natural. Effects of inbreeding and heterozygosity on preweaning. Inbreeding depression and heterosis of litter size in mice volume 1 issue 2 j. Segregation pattern of fertility restoration in icph 2671 and icph 2740 83 4. 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.
Now epigenetic arabidopsis hybrids show that epigenetic diversity and regulation contribute to both. Inbreeding depression refers to the decrease or loss of fitness and strength which is mainly caused due to inbreeding. Evidence for outbreeding depression is much less extensive than evidence for inbreeding depression, but outbreeding depression is nevertheless a general genetic phenomenon. Based on recent studies in many species, the authors argue that both.
Due to inbreeding as homozygosity increases, there may be rapid loss of vigour as well as disease resistance property. This phenomenon is mainly seen in the self pollinated species as they do not show any inbreeding depression even though they do not show heterosis. Contemporary genetic theory of inbreeding depression and heterosis is evaluated, as are the experimental data concerning the strength of inbreeding depression. Heterosis, inbreeding depression and line performance in crosses of triticum aestivum 1m. Heterosis it is defined as the superiority of f 1 hybrid over both the parents in terms of yield or some other characters. Inbreeding depression and heterosis of litter size in mice. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. The benefits of increased hybrid vigor, which often occur crossing unrelated plants or animals, have been recognized for centuries. Mechanisms of inbreeding depression and heterosis for. In this paper, we are interested in inbreeding depression primarily as a factor that may promote the evolution of mechanisms to prevent selffertilization in hermaphrodite or monoecious plants darwin, 1877. Expected means and variances among inbred lines and their crosses. Cross pollinated species and species reproducing asexually are highly heterozygous.
Ranga agricultural university for the degree of master of science in agriculture is the result of original research work done by me. A loss of vigor and general health that sometimes characterizes organisms that are the product of inbreeding. Consequently, mating between individuals of such populations is far from random, this being affected among individuals occurring in proximity with each other in space. Effects of population size and isolation on heterosis, mean. Population biological fitness refers to an organisms ability to survive and perpetuate its genetic material. This concept probably arises from the fact that inbreeding depression. Spigler,1,2 konstantinos theodorou,3 and shumei chang4 1department of biology, temple university, 1900 n. Combining ability, heterosis and inbreeding depression analysis for using cms lines in long duration pigeonpea international journal of research studies in biosciences ijrsb page 9 of variances viz. Average heterosis it is the heterosis where f 1 is superior to mid parent value. Mar 29, 2016 genetical and physiological basis of heterosis and inbreeding 1. The bioeconomic importance of heterosis and the systems to take advantage of heterosis from generation to generation have been discussed by many. Inbreeding depression and heterosis of hybrids in f2 populations of. This process is experimental and the keywords may be updated as the learning algorithm improves. If you continue browsing the site, you agree to the use of cookies on this website.
Heterosis is due to masking of deleterious recessive alleles by dominant alleles 4. Heterosis is directly proportional to the number of dominant genes contributed by each parent 18. Over time, natural selection weeds deleterious alleles out of a population when the dominant deleterious alleles are expressed, they lower the carriers fitness, and fewer copies wind up in the next generation. The different sources of variation in inbreeding depression. These keywords were added by machine and not by the authors. Heterosis and inbreeding depression biotech articles. An investigation on heterosis and inbreeding depression in. Inbreeding depression for yield and yield related traits in cmsbased pigeonpea hybrids 78 4.
Genetic basis of heterosis and inbreeding depression in rice. Inbreeding depression is also related to high heterosis in f 1 hybrids and has to search for moderate type of heterosis which has some stability to have less inbreeding depression at f 2 level 3. Crossbreeding crossbreeding and inbreeding are to some degree opposites 2, 5. Inbreeding in animals and plants leads to the formation of weak and lowfertile offspring inbreeding depression. Files are available under licenses specified on their description page. Mechanisms of inbreeding depression and heterosis for profitable. Several crosses exhibited heterosis for various attributes, however the highest avp. Genetical and physiological basis of heterosis and inbreeding. For example, a population of 40 adders vipera berus, shown at right experienced inbreeding depression when farming activities in sweden. A free powerpoint ppt presentation displayed as a flash slide show on id. Genetic basis of inbreeding depression and heterosis.
Crosses between natural populations can result in heterosis if recessive or. Heterosis, inbreeding depression, various theories of. Nb4d2 hybrids proved to be a good specific combiner by making higher contribution towards heterosis both in f1 hybrids and inbreeding at f2 generation. Choose from 32 different sets of inbreeding depression flashcards on quizlet.
The genetic basis of reduced inbreeding depression in polyploids introduction inbreeding depression is the reduced fitness of inbred offspring relative to outbred offspring. Inbreeding depression 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. Pdf estimation of heterosis and inbreeding depression. Fitness and vigour relationship 14 inbreeding depression is the decline in fitness and vigour with decreased heterozygosity, whereas heterosis is the increase in fitness and vigour with increased heterozygosity.
Genetical and physiological basis of heterosis and inbreeding dev hingra ph. Heterosis and its utilization for crop improvement. Heterosis and inbreeding depression in f2 populations of. Inbreeding depression inbreeding depression and heterosis. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of. Heterosis, inbreeding depression and line performance.
Mechanisms of inbreeding avoidance include in plants. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. Heterosis or hybrid vigor is a phenomenon in which the f1 progeny is superior in characteristics than its inbred parents. One problem in studying outbreeding depression is the number of generations that may occur before outbreeding depression reveals itself. Pdf inbreeding depression and its evolutionary consequences. Nihar ranjan chattopadhyay, in induced fish breeding, 2017. Superiority of dominant alleles over recessive alleles 3. Heterosis in okra pdf in our study, 24 hybrids obtained by diallel cross between ecotypes of okra were subjected to analysis of their combining ability effects and hybrid vigor.
Their effects can be modeled on the same scale by assuming that heterosis is simply the removal of accumulated inbreeding depression within each breed. Bioinformatics and computational biology program of study committee. 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. Heterobeltiosis, relative heterosis, and standard heterosis in cmsbased pigeonpea hybrids at patancheru, 2010 kharif season 70 4. The heterosis in relation to the parents mean was advanced search browse by author or subject tag cloud. A cross is said to show heterosis if h 0, so that the f 1 mean is larger than the average of both parents. A heterosis study for some agronomic traits in oat baz. Partial dominance and epistatic interactions are key causal elements. Aslam chowdhry, 1muhammad lqbal, 2ghulam mahboob subhani and 1lhsan khaliq 1department of plant breeding and genetics, university of agriculture, faisalabad, pakistan 2wheat research institute, aari, faisalabad, pakistan. Onion, squash, pumpkin, sunflower are a few examples of plants showing low inbreeding depression. Expected means and variances among inbred lines and their crosses c.
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