Heterosis, combining ability and components of genetic. Plant breeding and genetics all semester notes pdf file. Impacts of crossbreeding american herefordhomepage. Types of heterosis there are three main types of heterosis. It is most widely known for its application in maize, where hybrids are the basis of nearly all commercial breeding programs worldwide. A broad view of the early concepts can be found in heterosis gowen, 1952a. Heterosis, inbreeding depression, various theories of heterosis heterosis and inbreeding depression cross pollinated species and species reproducing asexually are highly heterozygous. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. Expression of heterosis for productive traits in f1 eggplant solanum melongena l.
Heterosis is observed in almost every crop species studied, the application of this phenomenon for its commercial exploitation depends on. Heterosis and recombination loss are then considered as effects that each member country relayed to interbeef in the 602 603 files. Aims and objectives of plant breeding plant breeding is an art and science, which tells us ways and means to change the genetic architecture of plants so as to attain a particular objective. Heterosis it is defined as the superiority of f 1 hybrid over both the parents in terms of yield or some other characters. Heterosis refers to the superior productivity and stress tolerance of highly heterozygous individuals. Department of agriculture, agricultural research service, department of genetics, north carolina state university, raleigh, north carolina 27695. Heterosis definition types of heterosis heterosis in. Heterosis and combining ability for yield and yield. However, leng reports that row number is affected in widely different degrees by heterosis, and that number of kernels per row ear length is the only primary yield component in which large positive effects of.
Ppt heterosis powerpoint presentation free to view. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. Pdf estimation of heterosis and combining abilities of. This explanation of heterosis has been an undercurrent in ongoing discussions from 1936 east, 1936 to the present time e. Heterotic groups and patterns are of fundamental importance in hybrid breeding. Opinion paper heterosis, stress, and the environment. Since then, heterosis has been widely utilized in crop breeding, ly in mespecialaize. Heterosis, also called hybrid vigour, the increase in such characteristics as size, growth rate, fertility, and yield of a hybrid organism over those of its parents.
Heterosis can be defend as the superiority of f hybrid over both the parents in terms of yield and some other character or. A guide for hand pollination of tomato flowers for breeding and seed production step 1. Average heterosis it is the heterosis where f 1 is superior to mid parent value. Improved heterosis prediction by combining information on. Improving plants using hybrid vigor module agronomy and. Storing heterosis and recombination loss another option is for interbeef to store not compute the heterosis and recombination loss calculated at the national level. Classical tomato heterosis is driven predominantly by qtl that control reproductive traits that integrate multiplicatively16,22.
The present roadmap for plant breeding takes a look at usdas roles and achievements in plant breeding, and at recent stakeholder input, to map out ways in which usdas plant breeding work can contribute to ongoing success and future preparedness across all sectors of u. Shull 1952 coined the term heterosis and defined it as. Despite such an extensive use in agriculture, the underlying mechanisms of heterosis are still poorly understood. Assessment of heterosis in two arabidopsis thaliana common. One of the reasons for using such wide crosses is to obtain heterosis. Plant and animal breeders exploit heterosis by mating two different purebred lines that have certain desirable traits. Hybrid vigour, or heterosis, has been of tremendous importance in agriculture for the improvement of both crops and livestock. 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 is a common phenomenon in maize, rice and. In my opinion, hybrid corn is the most far reaching development in applied biology in this quarter century mangelsdorf, 1951. Pdf hybrid wheat offers promises to break the yield stagnation in global wheat productivity due to heterosis. Heterosis is a multigenic complex trait and can be extrapolated as the sum total of many physiological and phenotypic traits. Submitted to submitted by derpartment of genetics and plant breeding, college of agriculture, jau, junagadh. Plant height, biomass, harvest index, number of primary branches, number of pods per plant, number of seeds per plant, 100seed weight and seed yield were recorded for each plant 10 observation. Mechanisms of inbreeding depression and heterosis for profitable dairying bennet cassell extension dairy scientist, genetics and management. Central to the concept of hybrid breeding is the phenomenon of heterosis or hybrid vigour i, which essentially describes the superiority of the hybrid line derived from two parental inbred lines with respect to numerous parameters, with yield being the. When two homozygous inbreeds a true breeding line obtained by continuous inbreeding of genetically unlike constituents are crossed together, the resulting hybrids obtained from. Plant heterosis shouqian feng, xiaoliu chen, shujing wu. The genetics and exploitation of heterosis in crops. Notwithstanding large efforts to study the phenomenon of heterosis in the last decades, the identification of common molecular mechanisms underlying hybrid vigour remain rare. Crosses showing heterosis in yield also showed heterosis in characters related to seedlings, mature fruits, plant growth, and fruit and seed size. Heterosis associated gene expression in maize embryos 6 days after fertilization exhibits additive, dominant and overdominant pattern.
Heterosis is retained in the breeding of crossbred animal and is related to the probability of alleles from different parental lines joining together. Various models have been posited to explain heterosis, including dominance, overdominance, and pseudooverdominance. Edwards heterosis is the foundation of modern maize breeding programs. Heterosis breeding and inbreeding depression authorstream. Computation of heterosis and recombination loss heterosis and recombination loss computation are directly derived from the breed composition of parents and are very different whether the computation was done using interbeef or icbf pedigrees. In the late 1990s, it was estimated that 65% of the worldwide maize zea mays area was planted as hybrids. The offspring of a f1 female will benefit from maternal heterosis 3. Heterosis and combining ability were studied for characters, viz. Importance of plant breeding, cytological principles of plant breeding, heterosis, inbreeding and its consequences or applications, selfincompatibility in plants, cytoplasmic male sterility, breeding. Plant breeding can be accomplished through many different techniques ranging.
Mechanisms of inbreeding depression and heterosis for. Despite its importance in maize production, we know surprisingly little about the genetic basis of heterosis. Heterosis of agronomic characters in jatropha jatropha. Heterosis and combining ability for yield and yield components were determined in a population derived from half diallel crossing of six cotton genotypes. Full text of plant breeding principles and methods see other formats. A summary of literature has established the following values for heterosis. 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. The prevalence of heterosis in natural populations as well as domesticated species has long intrigued geneticists, and research has extended from basic studies on the genetic nature of heterosis to practical applications in animal and plant breeding. Inbreeding has been used to great advantage in plant species where generation intervals tend to be short. In this article we will discuss about heterosis or hybrid vigour. Heterosis for some physiomorphological plant traits in spring wheat crosses shahzadi mahpara1, muhammad ishaq asif rehmani2, safdar hussain2, javaid iqbal2, muhammad kamran qureshi3, muhammad ahmed shehzad4 and javed shabbir dar5 1. Here, we conducted a systematic survey of the degree of heterosis in arabidopsis thaliana. The firstgeneration offspring generally show, in greater measure, the desired characteristics of both parents. Four crosses showed significant heterosis in yield per plant.
Strategies for utilizing heterosis in wheat, rice and oil seed brassica in india, pp. Hybridization and heterosis shull 1908, east 1936, gardner 1963 biotechnology. More branches per panicle and more grains per branch. Plant breeding is the art and science of changing the traits of plants in order to produce desired characteristics.
A study was conducted to assess the combining ability and heterosis of 14 parental lines by developing 91 single cross hybrids following half diallel mating design in maize at the department of genetics and plant breeding, uas, bengaluru. Structural polymorphisms as causes of heterosis in populus. Ir36 and ir42 yield 45 tha in wet season trials and 78 tha in dry season trials. Hand pollination of tomato for breeding and seed production. Heterosis of individual characters in each cross were calculated and tested for significance by a ttest. Maternal heterosis is the increase in performance of the crossbred cow relative to the average of straightbred females of the parental breeds. Heterosis is prevalent for multiple traits in diverse maize germplasm sherry a. Department of plant breeding and genetics, ghazi university, d. The flowering gene single flower truss drives heterosis. Plant breeding and genetics all semester notes pdf, principles of genetics pdf, introductory genetics see pdf, principles of plant breeding pdf, introductory plant breeding, principle of genetics and cytogenetics, principles of plant biotechnology pdf, fundamentals of food technology pdf, breeding of crops pdf, principles of genetics, history, mendels laws and exceptions, types of gene. The content of the module will address organization of germplasm into heterotic groups, prediction of.
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. An international symposium on heterosis in crops, 1722 august, 1997, mexico city, mexico. Heterosis most of the maize varieties grown in the u. Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. Studies conducted at the international rice research institute irri during 1980 and 1981 have shown up to 73% heterosis, 59% heterobeltiosis and 34% standard heterosis for yield in rice. Springer3 1usdaars, plant genetics research unit, and division of plant sciences, university of missouri, columbia, missouri, united states of america, 2usdaars, u. Heterosis is prevalent for multiple traits in diverse. Theoretical and experimental arguments are given demonstrating the superiority of intergroup compared with intragroup crosses under two aspects. Objectives communicate and discuss the discipline of practical plant breeding and its importance to us. Heterosis for some physiomorphological plant traits in.
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