Effects of interference between selected loci on the. Heterosis and inbreeding depression biotech articles. Fundamentally about the effects of inbreeding and outbreeding. We here examine variation in inbreeding depression, heterosis, and outbreeding depression on lifehistory traits across a fulllife cycle, within a metapopulation of. Genetical and physiological basis of heterosis and inbreeding.
The estimate of heterosis and inbreeding depression are presented in table 1. The current study was conducted to evaluate the performance of f2 population for studying mean performance, heterotic effects and inbreeding depression in upland cotton for polygenic traits. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. Heterosis is considered to be of little importance in soybean l. Mar 29, 2016 genetical and physiological basis of heterosis and inbreeding 1. Indeed, heterosis and inbreeding depression scale with. Genetic basis of heterosis and inbreeding depression in. Key difference heterosis vs inbreeding depression breeding is a process which is used to create or produce offspring with desired phenotypes. The different sources of variation in inbreeding depression. Sep 17, 2018 in fact heterosis and inbreeding depression may be considered as the two opposite sides of the same coin. Heterosis is often discussed as the opposite of inbreeding depression although. Heterosis and inbreeding depression in two soybean single crosses joseph w. Jun 04, 2017 key difference heterosis vs inbreeding depression breeding is a process which is used to create or produce offspring with desired phenotypes. Learn inbreeding depression with free interactive flashcards.
In this study, we experimentally evaluate how lifetime inbreeding depression and drift load, estimated by heterosis, vary with census n c and effective estimated as genetic diversity, h e population size across six populations of the biennial sabatia angularis as well as present novel models of inbreeding depression and heterosis under. Estimates of heterosis and inbreeding depression for growth, yield and yield contributing traits in four crosses of okra. Expected means and variances among inbred lines and their crosses. Having to select the best plants from each population and having to make sure there is a large enough population to keep from inbreeding depression can be reason to cause depression among many home gardeners. Heterosis and inbreeding depression for seed cotton yield and yield attributing traits in intrahirsutum g. Based on recent studies in many species, the authors argue that both. Inbreeding depression and heterosis are related phenomena of fundamental importance to evolutionary biology and applied genetics. In contrast, heterosis, or hybrid vigor, is defined as the superiority of an f 1 hybrid over its parents s tuber 1994. Heterosis and inbreeding depression in f2 populations of. The magnitude of inbreeding depression, heterosis, and outbreeding depression was very variable along the life cycle in p. After 3 or 4 generations of selfing it is hard to maintain lines. Inbreeding depression refers to reduced fitness of progenies resulting from inbreeding s tebbins 1958. Because breeding populations have finite size and long pedigree histories, mild inbreeding always exists by this definition.
Heterosis or hybrid vigor is a phenomenon in which the f1 progeny is superior in characteristics than its inbred parents. Genetic basis of heterosis and inbreeding depression in rice oryza. Heterosis, otherwise known as outbreeding enhancement, is the opposite of inbreeding depression and is sometimes referred to as hybrid vigor. 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. When a population is small or inbred, it tends to lose genetic diversity. Inbreeding depression observed in medicago sativa l. The restoration of phenotypic performance by crossing inbred lines to produce a hybrid is called heterosis. Pdf inbreeding depression and its evolutionary consequences. Inbreeding depression and heterosis of litter size in mice. In fact heterosis and inbreeding depression may be considered as the two opposite sides of the same coin. Explore the effects of inbreeding depression on animals, and plants. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility.
The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. It refers to decrease in fitness and vigour due to inbreeding or it may be defined as the reduction or. Inbreeding depression refers to the reduced vigor in the offspring from matings involving related parents. Contemporary genetic theory of inbreeding depression and heterosis is evaluated, as are the experimental data. Oct 01, 2015 indeed, heterosis and inbreeding depression scale with. Pdf genetic basis of heterosis and inbreeding depression in rice. Inbreeding depression and drift load in small populations. On the other hand, the positive and significant value was considerable for characters. Based on degree of depression, the plant species can be grouped into four broad categories.
Inbreeding in animals and plants leads to the formation of weak and lowfertile offspring 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. The converse or complement to inbreeding depression in which the value d a. Hybrid vigor is the opposite of inbreeding depression and is described as the masking of recessives through crossing of unrelated genotypes. Analyses of variance were performed and heterosis, inbreeding depression and reciprocal effects were calculated, each by two different methods, and tested for significance. Inbreeding inbreeding mating of related individuals mating of individuals more closely resulted by ancestry than would be expected under mating. Inbreeding depression and heterosis in most populations of animals, or higher plants, mobility is restricted. The negative and significant value of heterosis was considered desirable for days to flowering, days to maturity and plant height. Difference between heterosis and inbreeding depression.
Inbreeding depression and heterosis in autotetraploids. Ppt heterosis powerpoint presentation free to view. Genetic basis of inbreeding depression and heterosis. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield and or some other characters. 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.
Heterosis breeding and inbreeding depression authorstream. 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. Plant breeding is a common practice to develop new varieties and cultivar with beneficial characteristics. Burton and cavell brownie abstract heterosis is considered to be of little importance in. We used next generation sequencing technologies and a sample of the most elite.
Several crosses exhibited heterosis for various attributes, however the highest avp. Pdf the genetic basis of heterosis was studied through midparent, standard. Inbred strains tend to be homozygous for recessive alleles that are mildly harmful or produce a trait that is undesirable from the standpoint of the breeder. Ppt inbreeding and inbreeding depression powerpoint. Heterosis and inbreeding depression in two soybean single. The study included 12 cultivars, with seven assigned to the bsss heterotic group and five assigned to. Heterosis, inbreeding depression, various theories of heterosis heterosis and inbreeding depression cross pollinated species and species reproducing asexually are highly heterozygous. The contribution of epigenetic factors to inbreeding depression and heterosis remains elusive. 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.
Forage yield often is reduced by 30 percent or more after one generation of selfing, while f. Inbreeding depression and its evolutionary consequences. Know about inbreeding and inbreeding depression, along with the degrees of depression. This paper examines the extent to which empirical estimates of inbreeding depression and interpopulation heterosis in subdivided populations, as well as the effects of local population size on mean fitness, can be explained in terms of estimates of mutation rates, and the distribution of selection coefficients against deleterious mutations provided by population genomics data. A loss of vigor and general health that sometimes characterizes organisms that are the product of inbreeding. Inbreeding varsha uphar hb32 hb27 pusa sawani depression %. Overdominant epistatic loci are the primary genetic basis of. Heterosis is common and inbreeding depression absent in.
Mechanisms of inbreeding depression and heterosis for profitable. Hybrid vigor in plants and its relationship to insect pollination pdf. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of dollars of sales and investments in.
Crop science abstract heterosis, inbreeding depression. Estimates of heterosis and inbreeding depression for crosses of. Choose from 32 different sets of inbreeding depression flashcards on quizlet. Now epigenetic arabidopsis hybrids show that epigenetic diversity and regulation contribute to both. Estimates of inbreeding depression from f 2 over f 1. Consequently, mating between individuals of such populations is far from random, this being affected among individuals occurring in proximity with each other in space. Inbreeding appears universally to reduce fitness, but its magnitude and specific effects are highly variable because they depend on the genetic constitution of the species or populations and on how these genotypes interact with the environment. Inbreeding depression and heterosis of litter size in mice volume 1 issue 2 j. Mar 12, 2017 know about inbreeding and inbreeding depression, along with the degrees of depression. Mutational load, inbreeding depression and heterosis in. 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. Genetical and physiological basis of heterosis and inbreeding 1.
It refers to decrease in fitness and vigour due to inbreeding or it may be defined as the reduction or loss in vigour and fertility as a result of inbreeding. The level of heterosis in f 1 and f2generations along with inbreeding depression for all the crosses are presented in table 1. Mechanisms of inbreeding depression and heterosis for. Heterosis, inbreeding depression, various theories of. Heterosis and inbreeding depression 2019 natural remedy. Moreover, drift and selection should remove strongly deleterious recessive alleles from individual populations, resulting in reduced inbreeding depression. Inbreeding depression is often the result of a population bottleneck. Inbreeding depression in conservation biology annual. Inbreeding is the method of reproduction that involves mating of individuals that are closely related to each other genetically. Shekawat2 1department of plant breeding and genetics, rajasthan agricultural research institute, sknau, jobner, durgapura rajasthan, india. Inbreeding depression is of major concern in the management and conservation of endangered species. Inbreeding depression, heterosis, and outbreeding depression reveal differential impacts of mutations along the life cycle.
Hybrid cotton production through exploitation of heterosis is the only way for having vertical improvement and betterment in seed cotton yield which has been stagnated in the recent years. Inbreeding depression is the loss of fitness due to loss of genetic diversity. Estimates of heterosis and inbreeding depression for. 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. Pdf heterosis and inbreeding depression for economic traits in. High inbreeding depression inbreeding leads to severe depression and exhibit lethal effects. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield andor some other characters. Genetical and physiological basis of heterosis and inbreeding dev hingra ph. That is with exception of the maize family, which requires 200 plants to keep from exhibiting inbreeding depression. Two of them, proposed within the first decade after rediscovery of mendels work, claimed wide acceptance. Population biological fitness refers to an organisms ability to survive and perpetuate its genetic material. Glycine max, soybeans, plant breeding, crossing, heterosis, cultivars, inbred lines, inbreeding depression, selfing, crop yield, seed productivity, dominance genetics, loci, alleles abstract.