Plant breeding is a common practice to develop new varieties and cultivar with beneficial characteristics. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of. Heterosis seems to be mainly produced by the presence of com plementary sets of deleterious recessive alleles within both parental populations and the masking. Overdominant epistatic loci are the primary genetic basis of. Segregation pattern of fertility restoration in icph 2671 and icph 2740 83 4. Darwin 1876 also reported that inbreeding in plants results in deterioration of vigour and the crossing in hybrid vigour. Singh2 1horticulture, pjtsau, hyderabad, telangana, india. Heterobeltiosis, relative heterosis, and standard heterosis in cmsbased pigeonpea hybrids at patancheru, 2010 kharif season 70 4. The contribution of epigenetic factors to inbreeding depression and heterosis remains elusive. Contemporary genetic theory of inbreeding depression and heterosis is evaluated, as are the experimental data. Learn inbreeding depression with free interactive flashcards. We used next generation sequencing technologies and a sample of the most elite. Edwards heterosis is the foundation of modern maize breeding programs. Evolutionary theory suggests that the intensity of inbreeding depression, and hence the.
Combining ability, heterosis and inbreeding depression. Expected means and variances among inbred lines and their crosses. Genetic basis of heterosis and inbreeding depression in rice. Genetical and physiological basis of heterosis and inbreeding dev hingra ph. A study on heterosis and inbreeding depression in sunflower helianthus annuus l. Inbreeding depression and low betweenpopulation heterosis in. Inbreeding depression results due to fixation of unfavourable recessive genes in f2 fitness and vigour relationship. Heterosis and inbreeding depression studies for yield and yield related traits in tomato solanum lycopersicum l. Heterosis and inbreeding depression studies for yield and.
Shull 1952 coined the term heterosis and defined it as. Study of heterosis and combining ability for yield and yield contributing traits in barley hordeum vulgare l. Heterosis, inbreeding depression and line performance in crosses of triticum aestivum 1m. Hybrid vigor, or heterosis, is the increase in stature, biomass, and fertility that characterizes the progeny of crosses between diverse parents such that the f 1 is superior to the better of the two parents.
Genetical and physiological basis of heterosis and inbreeding 1. The genetic basis of reduced inbreeding depression in. Decoupling the variances of heterosis and inbreeding. 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. Inbreeding depression for yield and yield related traits in cmsbased pigeonpea hybrids 78 4.
Expected means and variances among inbred lines and their crosses c. Heterosis refers to the phenomenon that progeny of diverse varieties of. 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. Inbreeding depression for this trait was significant in f 2 of both crosses. It is a sixth largest source of vegetable oil in the world and can boost up the economy of any country by pro. Pdf study of heterosis and combining ability for yield. Winn1 1department of biological science, florida state university, tallahassee, fl 323064295, usa. Overdominant epistatic loci are the primary genetic basis. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield andor some other characters. Inbreeding depression and heterosis of hybrids in f2 populations of maize in the sao paulo state, brazil. It may be seen from the present study that the hybrid combinations, that showed higher estimates of heterosis in general found. Assuming an island model of population structure and weak selection, we express the mutation load, the within and betweendeme inbreeding depression, and heterosis as functions of the frequency of deleterious mutants in the metapopulation. Heterosis and inbreeding depression in two soybean single crosses joseph w.
Shull 1914 reported that high inbreeding depression positive is the reflection of heterosis especially in cross pollinated crop like maize and sorghum. Choose from 32 different sets of inbreeding depression flashcards on quizlet. Heterosis and inbreeding depression in two soybean single crosses. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. Two of them, proposed within the first decade after rediscovery of mendels work, claimed wide acceptance. Nb4d2 hybrids proved to be a good specific combiner by making higher contribution towards heterosis both in f1 hybrids and inbreeding at f2 generation. The analysis of variance revealed significant differences among. Although the production of hybrids from inbred lines allows one to fix heterosis, hybrids also provide many. Onion, squash, pumpkin, sunflower are a few examples of plants showing low inbreeding depression.
Mar 18, 2015 inbreeding depression for most of the characters was positive indicating that selection could be practiced in latter generations. Key difference heterosis vs inbreeding depression breeding is a process which is used to create or produce offspring with desired phenotypes. Evidence for outbreeding depression is much less extensive than evidence for inbreeding depression, but outbreeding depression is nevertheless a general genetic phenomenon. The different sources of variation in inbreeding 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. Hybrid vigor in plants and its relationship to insect pollination pdf. Heterosis and inbreeding depression for seed cotton yield and. Original article heterosis and outbreeding depression in crosses between natural populations of arabidopsis thaliana cg oakley1, j agren2 and dw schemske3 understanding the causes and architecture of genetic differentiation between natural populations is of central importance in. 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. A free powerpoint ppt presentation displayed as a flash slide show on id.
Based on recent studies in many species, the authors argue that both. Heterosis is often discussed as the opposite of inbreeding depression. Combining ability analysis gca enables plant breeders to select parental lines for crossing and provides the opportunity to understand the nature of gene actions involved in the inheritance of desired traits. Inbreeding depression inbreeding depression and heterosis. Hybrid vigor is the opposite of inbreeding depression and is described as the masking of recessives through crossing of unrelated genotypes.
Inbreeding depression and partitioning of genetic load 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. Seven parents in five cross combinations were studied for heterosis in f1 and inbreeding depression in f2 populations fornumber of bolls per plant, boll weight, halo length, ginning outturn and. The level of heterosis in f 1 and f2generations along with inbreeding depression for all the crosses are presented in table 1. Heterosis and combining ability analysis in cms hybrid. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of.
Heterosis and inbreeding depression in f2 populations of. The effect of inbreeding rate on fitness, inbreeding depression and heterosis over a range of inbreeding coefficients. Due to inbreeding each line becomes increasingly homozygous, as a consequence the variation within a line decrease rapidly. Mar 29, 2016 genetical and physiological basis of heterosis and inbreeding 1. Average heterosis it is the heterosis where f 1 is superior to mid parent value. Inbreeding depression and heterosis arise from the effects of gene combinations, that is, the effects of pairs of genes. The full text of this article is available as a pdf 192k. As with inbreeding depression, directional dominance is required for heterosis. This increased productivity or superiority over the parents is known as heterosis or hybrid vigor or.
The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Learn about the comparison between inbreeding depression and hybrid vigour. 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. Ppt inbreeding and inbreeding depression powerpoint. Jun 04, 2017 key difference heterosis vs inbreeding depression breeding is a process which is used to create or produce offspring with desired phenotypes. Department of plant biology, michigan state university, east lansing, mi 4882412, usa. Several crosses exhibited heterosis for various attributes, however the highest avp. High heterosis displayed by seed yield per plant may be due to pods per plant, branches per pant and plant height. Heterosis breeding and inbreeding depression authorstream. Inbreeding depression and its evolutionary consequences. The selfpollinated crops do not show inbreeding depression. Positive heterosis over better parent was reported by tuteja et al. Heterosis and inbreeding depression biotech articles.
A study on heterosis and inbreeding depression in sunflower. Heterosis and inbreeding depression kana ram kumawat, ravi kumawat and madhu choudhary department of plant breeding and genetics, s. 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. Genetical and physiological basis of heterosis and inbreeding. Genetic basis of heterosis and inbreeding depression in. Heterosis it is defined as the superiority of f 1 hybrid over both the parents in terms of yield or some other characters. Pdf inbreeding depression and its evolutionary consequences. Although the production of hybrids from inbred lines allows one to fix heterosis, hybrids also provide many other advantages in a crop production system. Difference between heterosis and inbreeding depression. Many experiments led to the definition of the relations hipbetweentheincrease in the inbreeding coefficient and the quantitative performance. 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. Ppt heterosis powerpoint presentation free to view.
Heterosis definition types of heterosis heterosis in. The benefits of increased hybrid vigor, which often occur crossing unrelated plants or animals, have been recognized for centuries. One of the fascinating techniques of plant breeding the heterosis, know about the hypothesis and application in plant breeding. The study of hybrid vigor and inbreeding depression traces back to charles darwin, who was the first scientist to examine the phenomenon in a systematic manner. Zea mays exhibits significant heterosis and inbreeding depression, and despite billions of dollars of sales and investments in hybrid maize, the underlying molecular and genetic mechanisms responsible for inbreeding depression and heterosis still remain unknown. Inbreeding depression an overview sciencedirect topics. Inbreeding depression and heterosis in rice, ii 1757 table 1 equations for calculating hb of the lemontteqing rils and the midparental heterosis h mp of the two bcf 1 and two testcross f 1 populations populationa n equationsb rils 254 hb ril mp, where mp lemont teqing2 ltbcf 1 172 h mp f 1 mp, where mp ril lemont2 tqbcf 1 177 h. After 78 generations of selfing, the lines becomes almost uniform 99% homozygosity which are called inbred. Inbreeding in animals and plants leads to the formation of weak and lowfertile offspring inbreeding depression. Pdf the effect of inbreeding rate on fitness, inbreeding. The level of inbreeding depression has been suggested to determine a plants mating. An investigation on heterosis and inbreeding depression in.
The genetic basis of reduced inbreeding depression in polyploids. Effects of population size and isolation on heterosis, mean. Effects of population size and isolation on heterosis. Now epigenetic arabidopsis hybrids show that epigenetic diversity and regulation contribute to both. Heterosis, inbreeding depression and line performance. Agriculture university jobner303329, jaipur, rajasthan, india email. A heterosis study for some agronomic traits in oat baz. One problem in studying outbreeding depression is the number of generations that may occur before outbreeding depression reveals itself. This concept probably arises from the fact that inbreeding depression. The genetic basis of reduced inbreeding depression in polyploids introduction inbreeding depression is the reduced fitness of inbred offspring relative to outbred offspring.
An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. Despite its importance in maize production, we know surprisingly little about the genetic basis of heterosis. Heterosis is a multigenic complex trait and can be extrapolated as the sum total of many physiological and phenotypic traits. Heterosis or hybrid vigor is a phenomenon in which the f1 progeny is superior in characteristics than its inbred parents. Pdf heterosis and inbreeding depression for economic traits. Crosses between natural populations can result in heterosis if recessive or nearly recessive deleterious.
In this study we used recently diverged experimental populations to which we applied selfpollination, within and betweenpopulation crosses to investigate the link between the genetic structure of the subdivided population, and fitnessrelated traits values in the firstgeneration offspring, by assessing withinpopulation heterosis or. Heterosis or hybrid vigor has been a major factor in the increased pro. A cross is said to show heterosis if h 0, so that the f 1 mean is larger than the average of both parents. 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. Heterosis, inbreeding depression, various theories of. A loss of vigor and general health that sometimes characterizes organisms that are the product of inbreeding. 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. Heterosis and outbreeding depression in crosses between natural. Mechanisms of inbreeding depression and heterosis for. Inbreeding depression and heterosis of hybrids in f2 populations of. Cross pollinated species and species reproducing asexually are highly heterozygous. Materials and methods study species distribution and life history in north america, a. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of dollars of sales and investments in.
Joint effects of selffertilization and population structure on mutation load, inbreeding depression and heterosis. Ppt heterosis powerpoint presentation free to view id. The genetic interpretation of inbreeding depression and. 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. Heterosis and inbreeding depression study in cowpea vigna unguiculata l. 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. The converse or complement to inbreeding depression in which the value d a inbreeding can result in loss of vigor, size, etc.
When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield and or some other characters. Genetic basis of inbreeding depression and heterosis. Burton and cavell brownie abstract heterosis is considered to be of little importance in soybean glycine max l. Shell weight showed low level of heterosis in f1 hybrids 14 to 20 %, whereas the effect of inbreeding depression in f2 progeny was 4. Inbreeding depression, inbreeding depression and heterosis, genetics. Now epigenetic arabidopsis hybrids show that epigenetic diversity and. Inbreeding depression definition of inbreeding depression. 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. Heterosis can be defend as the superiority of f hybrid over both the parents in terms of yield and some other character or. Heterosis, otherwise known as outbreeding enhancement, is the opposite of inbreeding depression and is sometimes referred to as hybrid vigor. Heterosis and outbreeding depression in crosses between. 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.
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