F1 hybrid

Last updated

An F1 hybrid (also known as filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. [1] F1 hybrids are used in genetics, and in selective breeding, where the term F1 crossbreed may be used. The term is sometimes written with a subscript, as F1 hybrid. [2] [3] Subsequent generations are called F2, F3, etc.

Contents

The offspring of distinctly different parental types produce a new, uniform phenotype with a combination of characteristics from the parents. In fish breeding, those parents frequently are two closely related fish species, while in plant and animal breeding, the parents often are two inbred lines.

Gregor Mendel focused on patterns of inheritance and the genetic basis for variation. In his cross-pollination experiments involving two true-breeding, or homozygous, parents, Mendel found that the resulting F1 generation was heterozygous and consistent. The offspring showed a combination of the phenotypes from each parent that were genetically dominant. Mendel's discoveries involving the F1 and F2 generations laid the foundation for modern genetics.

Production of F1 hybrids

In plants

Crossing two genetically different plants produces a hybrid seed. This can happen naturally, and includes hybrids between species (for example, peppermint is a sterile F1 hybrid of watermint and spearmint). In agronomy, the term F1 hybrid is usually reserved for agricultural cultivars derived from two-parent cultivars. These F1 hybrids are usually created by means of controlled pollination, sometimes by hand pollination. For annual plants such as tomato and maize, F1 hybrids must be produced each season.

For mass production of F1 hybrids with uniform phenotype, the parent plants must have predictable genetic effects on the offspring. Inbreeding and selection for uniformity for multiple generations ensures that the parent lines are almost homozygous. The divergence between the (two) parent lines promotes improved growth and yield characteristics in offspring through the phenomenon of heterosis ("hybrid vigour" or "combining ability").

Two populations of breeding stock with desired characteristics are subjected to inbreeding until the homozygosity of the population exceeds a certain level, usually 90% or more. Typically, this requires more than 10 generations. Thereafter, the two strains must be crossed, while avoiding self-fertilization. Normally, this is done with plants by deactivating or removing male flowers from one population, taking advantage of time differences between male and female flowering, or hand pollinating. [4]

In 1960, 99% of all corn, 95% of sugar beet, 80% of spinach, 80% of sunflowers, 62% of broccoli, and 60% of onions planted in the United States were F1 hybrids.[ citation needed ] Beans and peas are not commercially hybridized because they are automatic pollinators, and hand pollination is prohibitively expensive.


F2 hybrids

F2 hybrids, the result of self or cross-pollination of F1s, lack the consistency of F1s, though they may retain some desirable traits and can be produced more cheaply because hand pollination or other interventions are not required. Some seed companies offer F2 seed at less cost, particularly in bedding plants, where consistency is less critical. [5]

In animals

F1 crosses in animals can be between two inbred lines or between two closely related species or subspecies. In fish such as cichlids, the term F1 cross is used for crosses between two different wild-caught individuals that are assumed to be from different genetic lines. [6]

Mules are F1 hybrids between horses (mares) and donkeys (jacks); the opposite sex cross results in hinnies.[ citation needed ] However, such offspring are almost always sterile.

Today, certain domesticatedwild hybrid breeds, such as the Bengal cat and the Savannah cat, are classified by their filial generation number. An F1 hybrid Savannah cat is the result of reproduction between an African Serval cat and a domestic cat.

As explained in the International Journal of Fauna and Biological Studies,[ citation needed ] there are four reasons for species hybridizations:

  1. Small population size
  2. Habitat fragmentation and species introduction
  3. Anthropogenic hybridization
  4. Visual, chemical, and acoustic interferences

Small population size can be caused by inadequate or obliterated natural habitats that lead to species escaping to other habitats and as a result, this may lead to lesser mate availability and can cause breeding between distinct species. [7] Habitat fragmentation and species introduction can be man-made or caused by mother nature such as deforestation, desertification, eutrophication, urbanization, water oil extraction causing changes in the ecosystem that leads to animal migration or evading new surroundings. [8] Third, is anthropogenic hybridization, which is "artificial or human-led hybridization" is supported for researchers to study "reproductive compatibility between species". [9] Lastly, visual, chemical, and acoustic interferences cues are what causes species to signal sexual cues by differentiating between the same and opposite-sex leading to hybridization. [10]

Advantages

The advantages of species hybridization are 1.) evolution of new interspecific breed, 2.) hybrid vigour, and 3.) enhanced longevity and immunity to diseases (Dubey, A. 2019). Dubey explains each as follows: 1.) A new interspecific breed is due to the mating of two distinguished species. 2.) Hybrid vigour is defined as a species becoming sturdier, more dynamic, and stronger than the parents. Lastly, 3.) Hybrids can have improved longevity and are "highly immune to diseases" (Dubey, A. 2019).

Disadvantages

In contrast, the limitations can be due to genetic extinction and/or outbreeding depression. Dubey explains that genetic extinction can be caused by "hybrid swarms" noting the various degrees of hybrids. [11] Outbreeding depression is the "cross between genetically distant populations" causing hybrids to reduce fit and isolation leading to reduced reproduction. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Mendelian inheritance</span> Type of biological inheritance

Mendelian inheritance is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularized by William Bateson. These principles were initially controversial. When Mendel's theories were integrated with the Boveri–Sutton chromosome theory of inheritance by Thomas Hunt Morgan in 1915, they became the core of classical genetics. Ronald Fisher combined these ideas with the theory of natural selection in his 1930 book The Genetical Theory of Natural Selection, putting evolution onto a mathematical footing and forming the basis for population genetics within the modern evolutionary synthesis.

<span class="mw-page-title-main">Hybrid (biology)</span> Offspring of cross-species reproduction

In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera. Hybrids are not always intermediates between their parents, but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are.

<span class="mw-page-title-main">Dominance (genetics)</span> One gene variant masking the effect of another in the other copy of the gene

In genetics, dominance is defined as the interactions between alleles at the same locus on homologous chromosomes and the associated phenotype. In the case of complete dominance, one allele in a heterozygote individual completely overrides or masks the phenotypic contribution of the other allele. The overriding allele is referred to as dominant and the masked one recessive. Complete dominance, also referred to as Mendelian inheritance, follow Mendel's laws of segregation. The first law states that each allele in a pair of genes is separated at random and have an equal probability of being transferred to the next generation, while the second law states that the distribution of allele variants is done independently of each other. However, this is not always the case as not all genes segregate independently and violations of this law are often referred to as "non-Mendelian inheritance".

<span class="mw-page-title-main">Quantitative genetics</span> Study of the inheritance of continuously variable traits

Quantitative genetics is the study of quantitative traits, which are phenotypes that vary continuously—such as height or mass—as opposed to phenotypes and gene-products that are discretely identifiable—such as eye-colour, or the presence of a particular biochemical.

Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of its parents. The heterotic offspring often has traits that are more than the simple addition of the parents' traits, and can be explained by Mendelian or non-Mendelian inheritance. Typical heterotic/hybrid traits of interest in agriculture are higher yield, quicker maturity, stability, drought tolerance etc.

Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, to achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and production of gene knockout organisms.

A crossbreed is an organism with purebred parents of two different breeds, varieties, or populations. Crossbreeding, sometimes called "designer crossbreeding", is the process of breeding such an organism. While crossbreeding is used to maintain health and viability of organisms, irresponsible crossbreeding can also produce organisms of inferior quality or dilute a purebred gene pool to the point of extinction of a given breed of organism.

<span class="mw-page-title-main">Open pollination</span> Pollination by natural agents, or true-breeding in plant varieties

"Open pollination" and "open pollinated" refer to a variety of concepts in the context of the sexual reproduction of plants. Generally speaking, the term refers to plants pollinated naturally by birds, insects, wind, or human hands.

In agriculture and gardening, hybrid seed is produced by deliberately cross-pollinated plants which are genetically diverse. Hybrid seed is common in industrial agriculture and home gardening. It is one of the main contributors to the dramatic rise in agricultural output during the last half of the 20th century. Alternatives to hybridization include open pollination and clonal propagation.

<span class="mw-page-title-main">Monohybrid cross</span> Cross between two organisms with different variations at one genetic locus of interest

A monohybrid cross is a cross between two organisms with different variations at one genetic locus of interest. The character(s) being studied in a monohybrid cross are governed by two or multiple variations for a single location of a gene. Then carry out such a cross, each parent is chosen to be homozygous or true breeding for a given trait (locus). When a cross satisfies the conditions for a monohybrid cross, it is usually detected by a characteristic distribution of second-generation (F2) offspring that is sometimes called the monohybrid ratio.

Inbreeding depression is the reduced biological fitness that has the potential to result from inbreeding. Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. Inbreeding depression is often the result of a population bottleneck. In general, the higher the genetic variation or gene pool within a breeding population, the less likely it is to suffer from inbreeding depression, though inbreeding and outbreeding depression can simultaneously occur.

In biology, outbreeding depression happens when crosses between two genetically distant groups or populations result in a reduction of fitness. The concept is in contrast to inbreeding depression, although the two effects can occur simultaneously. Outbreeding depression is a risk that sometimes limits the potential for genetic rescue or augmentations. It is considered postzygotic response because outbreeding depression is noted usually in the performance of the progeny.

<span class="mw-page-title-main">Test cross</span>

Under the law of dominance in genetics, an individual expressing a dominant phenotype could contain either two copies of the dominant allele or one copy of each dominant and recessive allele. By performing a test cross, one can determine whether the individual is heterozygous or homozygous dominant.

Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity.

Hybrid rice is a type of Asian rice that has been crossbred from two very different parent varieties. As with other types of hybrids, hybrid rice typically displays heterosis or "hybrid vigor", so when grown under the same conditions as comparable purebred rice varieties, it can produce up to 30% more yield. To produce hybrid seeds in large quantity, a purebred sterile rice variety is fertilized with fertile pollen from a different variety. High-yield crops, including hybrid rice, are one of the most important tools for combatting worldwide food crises.

A doubled haploid (DH) is a genotype formed when haploid cells undergo chromosome doubling. Artificial production of doubled haploids is important in plant breeding.

Foundation stock or foundation bloodstock refers to animals that are the progenitors, or foundation, of a breed or of a given bloodline within such. Many modern breeds can be traced to specific, named foundation animals, but a group of animals may be referred to collectively as foundation bloodstock when one distinct population provides part of the underlying genetic base for a new distinct population.

<span class="mw-page-title-main">Plant breeding</span> Humans changing traits, ornamental/crops

Plant breeding is the science of changing the traits of plants in order to produce desired characteristics. It has been used to improve the quality of nutrition in products for humans and animals. The goals of plant breeding are to produce crop varieties that boast unique and superior traits for a variety of applications. The most frequently addressed agricultural traits are those related to biotic and abiotic stress tolerance, grain or biomass yield, end-use quality characteristics such as taste or the concentrations of specific biological molecules and ease of processing.

Plant breeding started with sedentary agriculture, particularly the domestication of the first agricultural plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially, early human farmers selected food plants with particular desirable characteristics and used these as a seed source for subsequent generations, resulting in an accumulation of characteristics over time. In time however, experiments began with deliberate hybridization, the science and understanding of which was greatly enhanced by the work of Gregor Mendel. Mendel's work ultimately led to the new science of genetics. Modern plant breeding is applied genetics, but its scientific basis is broader, covering molecular biology, cytology, systematics, physiology, pathology, entomology, chemistry, and statistics (biometrics). It has also developed its own technology. Plant breeding efforts are divided into a number of different historical landmarks.

Classical genetics is the branch of genetics based solely on visible results of reproductive acts. It is the oldest discipline in the field of genetics, going back to the experiments on Mendelian inheritance by Gregor Mendel who made it possible to identify the basic mechanisms of heredity. Subsequently, these mechanisms have been studied and explained at the molecular level.

References

  1. Marschall S. Runge; Cam Patterson, eds. (2006). Principles of Molecular Medicine. Humana Press. p. 58. ISBN   978-1-58829-202-5.
  2. Peter Abramoff and Robert G. Thomson (1994). Laboratory Outlines in Biology--VI. Macmillan. p. 497. ISBN   978-0-7167-2633-3.
  3. William Ernest Castle and Gregor Mendel (1922). Genetics and eugenics: a text-book for students of biology and a reference book for animal and plant breeders. Harvard University Press. p.  101. Filial subscript.
  4. Hand Pollination
  5. Lawrence D. Hills (1987). "F2 and open-pollinated varieties". Growing from Seed (The Seed Raising Journal from Thompson & Morgan). 1 (2).
  6. "Guide to selecting and breeding high quality cichlids". bigskycichlids.com.
  7. Dubey, A. 2019
  8. Dubey, A. 2019
  9. Grabenstein and Taylor, 2018
  10. Grabenstein and Taylor, 2018
  11. Dubey, A. 2019
  12. Dubey, A. 2019