It should be thought that the heterosis observed in animal breeding is the increase in vigor that is seen in. The objective of the research was to estimate heterosis, heterobeltiosis, and gene action of several. Heterosis breeding and inbreeding depression authorstream. The evaluation of heterosis retention is based upon comparisons among various generations of a crossbreeding program. Heterosis is observed in almost every crop species studied, the application of this phenomenon for its commercial exploitation depends on. Plant and animal breeders exploit heterosis by mating two different purebred lines that have certain desirable traits. When these species are subjected to selfing or inbreeding they show severe reduction in. In an attempt to identify candidate genes reponsible for hybrid vigor, there has been a number of gene expression studies of hybrids vs their inbred parents for. Genomic architecture of heterosis for yield traits in rice. The phenomenon of heterosis or hybrid vigor has long been recognized to have a genetic basis. Outlines of the presentation possible genetic basis of heterosis dominance hypothesis overdominance hypothesis pseudo overdominance. Although there have been a range of studies on various aspects of heterosis, the key to understanding the biological mechanisms of heterotic performance in crop hybrids is the genetic basis, much of which.
Download figure open in new tab download powerpoint. To systematically exploit heterosis in hybrid breeding, the concept of heterotic groups and patterns was suggested. 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. While the practical application of heterosis in plant breeding is quite successful in many crops through the development of hybrid varieties, the basic understanding of the phenomenon is. Genetic analysis of heterosis for yield and yield components. Combining ability and heterosis for yield and component. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. In addition, the various genetic components to heterosis presented trait. The phenomenon heterosis hybrid vigour is well known in breeding as the increase in yield or size or other traits in hybrids.
Heterosis has been increasingly applied in crop production for nearly a century, with the aim of developing more vigorous, higher yielding and better performing cultivars. In the seminal heterosis conference held in 1952 at iowa state university, shull defined heterosis as the interpretation of increased vigour, size, fruitfulness, speed of development, resistance to disease and to insect pests, or to climatic rigors of any kind manifested by crossbred. Aug 21, 2019 a trial involving 10 parents and f1 hybrids was conducted for 3 yr. Edwards heterosis is the foundation of modern maize breeding programs. While the practical application of heterosis in plant breeding is quite successful in many crops through the development of hybrid varieties, the basic understanding of the phenomenon is not very advanced. Shull 1952 coined the term heterosis and defined it as. L george harrison shull2 princeton university, princeton, new jersey received april 21, 1948 i t is not my purpose in this paper to present or discuss the actual basic causes or the fundamental mechanisms which bring about the increased size, the excessive kinetic energy, the increased productiveness, resistance to. Heterosis or hybrid vigor is a natural phenomenon whereby hybrid offspring of genetically diverse individuals display improved physical and functional characteristics relative to their parents. Cbd heterotic patterns were created by breeders through trial and error. Insights into the genomic architecture of heterosis for grain yield in rice are presented, and further mapping of grain yield loci resolves candidate genes that could be useful for breeding.
Heterosis outbreeding and hybrid vigour presented to. Despite its importance in maize production, we know surprisingly little about the genetic basis of heterosis. Pdf heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of. The study of hybrid vigor and inbreeding depression traces back to charles darwin, who was the first scientist. Mechanisms of inbreeding depression and heterosis for profitable. A trial involving 10 parents and f1 hybrids was conducted for 3 yr. Weaber department of animal science and industry kansas state university introduction the dramatic changes and volatility cowcalf production system input costs and calf values have many producers wondering about the value of heterosis in todays beef. The mechanism by which this superiority is developed 6. In fact, the biological basis of heterosis is considered by some scientists to.
On the basis of divergence, ten accessions were selected and crossed in a diallel fashion without reciprocals to study the combining ability and heterosis. Efficient exploitation of heterosis is central for successful hybrid breeding in sunflower. Feb 28, 2017 one of the fascinating techniques of plant breeding the heterosis, know about the hypothesis and application in plant breeding. Here, hochholdinger and baldauf provide an overview of this fascinating biological phenomenon and what is known about the underlying genetics and mechanisms. Scribd is the worlds largest social reading and publishing site. Types of heterosis there are three main types of heterosis. Utilization of heterosis has contributed tremendously to the increased productivity in many crops for decades.
Results include data of mean values for grain yield and its components for 10 dry bean lines, and values of heterosis over the superior parent and heterisis depressions for yield and its components in crosses of dry bush beans. Ppt heterosis powerpoint presentation free to view id. Heterosis or hybrid vigor has been a major factor in the increased pro. Heterosis can be defend as the superiority of f hybrid over both the parents in terms of yield and some other character. Powerpoint to pdf convert your ppt to pdf for free online. Superiority of dominant alleles over recessive alleles 3. Software for the graphical presentation of linkage maps and qtls. In fact, the biological basis of heterosis is considered by some scientists to be inadequately defined. Department of agriculture, agricultural research service, department of genetics, north carolina state university, raleigh, north carolina 27695. Genetic analysis of heterosis although the genetic basis for heterosis has been studied for over a century hypotheses have been and several.
Heterosis, the increase in such characteristics as size, growth rate, fertility, and yield of a hybrid organism over those of its parents. Heterosis definition is the marked vigor or capacity for growth often exhibited by crossbred animals or plants called also hybrid vigor. Ganesan regional research station, tamil nadu agricultural university, vriddhachalam 606 001, tamil nadu, india abstract seven sesame genotypes were crossed ina diaiiei method without reclproca1s and heterosis over mp and bp were estimatedfor the yield and yield. Various models have been posited to explain heterosis, including dominance. Heterosis is observed in almost every crop species studied, the application of this phenomenon for its commercial exploitation depends on the expression of the degree of heterosis. These observations provide strong support for the model that trueoverdominant genes exist and can drive yield heterosis. Meat animal research center marc provide substantive and meaningful data on the value of crossbreeding. Heterosis is an important trait in developing of hybrid variety. Heterosis is directly proportional to the number of dominant genes contributed by each parent 18.
Heterosis is a major yield factor in all breeding categories except line breeding schnell, 1982. If true, it should not be possible to obtain an inbred that performs equally as well as the best hybrid bernardo 2002 breeding for quantitative traits in plants pp 243246. Heterosis and inbreeding depression iowa state university digital. Heterosis, hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. Convert your powerpoint to pdf online, easily and free. Cummins that interprets specific social cognitive functions as adaptations to the exigencies of living in a dominance or status hierarchy. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. Heterosis is retained in the breeding of crossbred animal and is related to the probability of alleles from different parental lines joining together. If we did not know that two loci comprise a single linkage block, we would incorrectly conclude that heterosis is due to overdominance. Pdf genetic basis of heterosis and prediction of hybrid performance. Cross pollinated species and species reproducing asexually are highly heterozygous.
Heterosis definition types of heterosis heterosis in. These elegant and truly remarkable germ plasm evaluation and germ plasm utilization studies at the u. The offspring of a f1 female will benefit from maternal heterosis 3. Genetics of heterosis pseudooverdominance hypothesis repulsion phase linkage of loci that show partial or complete dominance the effects of two loci are difficult to separate if both are tightly linked. Ppt to pdf convert file now view other document file formats technical details a large part of any presentation is how the text enters, appears and exits the screen. Combining ability heterosis maize plant breeding introduction types of hybrids, which exhibit high heterosis when the maize is the worlds most widely grown cereal and is uniformity. Heterosis, inbreeding depression, various theories of heterosis. To systematically exploit heterosis in hybrid breeding. Genetic basis of heterosis for yield and yield components explored. Heterosis is due to masking of deleterious recessive alleles by dominant alleles 4. Ppt heterosis powerpoint presentation free to download. In this perspective, we consider that it might be useful to the field to abandon these.
Genetic composition of yield heterosis in an elite rice. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. The converse or complement to inbreeding depression in which the value d a inbreeding can result in loss of vigor, size, etc. Despite the importance of heterosis in maize and the plethora of research done on heterosis, little is known empirically about the underlying genetic and related physiological basis of heterosis. The restoration of phenotypic performance by crossing inbred lines to produce a hybrid is called heterosis. Exploring the molecular basis of heterosis for plant breeding liu.
If we design breeding programs that capture direct and maternal heterosis, we can increase lifetime production by more than 20%. Hybrid vigor or heterosis is defined as a superior performance of hybrids, for many traits, relative to their parental inbred lines see chapter 8 of this book. One of the fascinating techniques of plant breeding the heterosis, know about the hypothesis and application in plant breeding. Owing to heterosis hybrid vigor in plants, these hybrids often have superior agricultural performances in yield or disease resistance.
Pdf hybrid vigor or heterocyst is the phenomenon in which progeny of crosses between inbred lines or. According to shull the developed superiority of the hybrids is the hybrid vigour. Jan 20, 2014 types of heterosis there are three main types of heterosis. A free powerpoint ppt presentation displayed as a flash slide show on id. It is generally agreed that hybrid vigour describes only superiority of the hybrid over the parents while heterosis describes the other situation as well i. Heterosis refers to the superior performance of hybrids relative to the parents. Varietal classification virginia no floral axis on main stem, alternating pairs of floral and vegetative axis on branches, branches short, less hairy peruvian runner no floral axis on main stem, alternating pairs of floral and vegetative axis on branches, long, more hairy valencia floral axis on main stem. Heterosis is the superior performance of f 1 hybrids relative to the midparent value mpv or to the better parent.
Heterosis can be classified into midparent heterosis, in which the hybrid shows increased strength which is greater than the average of both parents, and bestparent heterosis, in which the hybrids increased strength is greater than that of the strongest parent. 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, also known as hybrid vigor, is a wellknown phenomenon whereby hybrid offspring resulting from cross pollination exhibit greater vigor than either parent. Phenotypic variation of yield and yield components for the parents pdf 105 kb. Various models have been posited to explain heterosis, including dominance, overdominance, and pseudooverdominance. Sep 25, 2012 heterosis refers to the superior performance of hybrids relative to the parents. Hybrids have been widely used in crop and tree breeding since ancient times, although the molecular mechanisms underlying heterosis have yet to be fully elucidated. Mar 22, 2014 heterosis or hybrid vigor is a natural phenomenon whereby hybrid offspring of genetically diverse individuals display improved physical and functional characteristics relative to their parents.
Divergence of 25 accessions of brassica juncea of indian, cis commonwealth of independent states, former ussr and synthetic origin was studied by d 2 analysis. Midparent heterosis is more common in nature, and it is easier to explain by. Whereas continued inbreeding of outbreeding species leads to loss of vigour, f1 hybrids produced from inbred lines exhibit heterosis or hybrid vigour. Heterosis brinjal pdf nagai and kida were the first to observe hybrid vigor in eggplant. This hybrid vigor is determined by nonmutually exclusive mechanisms, including dominance complementation, overdominance and epistasis. Ppt heterosis powerpoint presentation free to view. Heterosis definition of heterosis by merriamwebster. Inbreeding depression and heterosis arise from the effects of gene combinations, that is, the effects of pairs of genes. Heterosis, heterobeltiosis, dan aksi gen beberapa karakter. Consequently, it is important to distinguish between genetic effects occurring in different generations such as individual heterosis in a maternal trait and heterosis in a maternal effect on individual performance. These observations provide strong support for the model that true.
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