Absorption (transformative) crossing consists in the fact that unproductive queens of one breed are crossed in a number of generations with producers of another highly productive breed. Thus, the properties of the improved rock are absorbed or displaced by the properties of the improving rock. The absorption process is stopped if the hybrids do not differ in productivity, conformation and constitution from the animals of the improving breed. In the future, such crossbreeds are bred "in themselves."
With each new generation of crossing, the “bloodliness” of the original (maternal) breed is reduced by half compared to the previous generation.
Transformative crossbreeding- one of the most common; its effectiveness largely depends on the crossing technique, the choice of the improving breed and the conditions of feeding and keeping animals.
The purpose of absorption crossbreeding is to radically improve animals of an unproductive breed. Crossbreeds obtained as a result of crossing during several generations of mating with purebred producers of the improving breed are brought to a high degree of similarity with the animals of the improving breed.
The offspring obtained by breeding "in itself" crossbreeds of the second generation (3/4 blood), depending on the severity of the desired type, are classified as crossbreeds of the fourth or third generation according to the improved breed. The offspring obtained as a result of breeding "in itself" crossbreeds of the third and fourth generations, depending on the severity of the desired type, are classified as crossbreeds of the fourth or third generations according to the breed being improved. The offspring obtained as a result of breeding "in itself" crossbreeds of the third and fourth generations, and the fourth generation, depending on the severity of the desired type, are classified as crossbreeds of the fourth generation or purebred animals. In the absence of documents on the origin of animals, but a good expression of the type of improving breed, they are referred to as crossbreeds of the first or second generations (1/2 - 3/4 bloodlines) of this breed.
Absorption crossbreeding- an important method for the transformation of unproductive animals, and it is often desirable to obtain those that, along with the improvement of economically useful qualities, would not lose some of the properties of local improved livestock.
When choosing an improving breed, it is important that the representatives of the latter significantly outperform the animals of the improved breed in terms of economically useful traits and, in addition, adapt well to local conditions.
As a result wide application transformational crossbreeding, the number of purebred animals in our country is increasing every year. The use of purebred producers of improving domestic and imported breeds has made it possible over the past 35-40 years to dramatically transform the main array of the country's animal porridge.
Before embarking on absorptive crossing, one should find out the characteristics of the improving breed, its adaptability to local conditions. So, in a number of regions of the country, little suitable for natural conditions for the breeding of fine-fleeced rams, the absorption crossing of local coarse-wooled sheep with fine-fleeced rams gives poor results.
The success of absorptive crossing also depends on the quality of the producers of the improving breed, as well as on the conditions of feeding and keeping the crossbred offspring. Only by creating favorable conditions for feeding and keeping hybrids can high rates be achieved.
The successful application of this method is facilitated by the strict selection of crossbreeds, the speed of generational change and the hereditary stability of the traits of the improving breed.
The value of absorption crossbreeding for the rapid mass improvement of the breed composition of animals. Absorption of blood bred many breeds of animals abroad and in our country. P. N. Kuleshov in his work “Methods of Pedigree Breeding of Domestic Animals” (1932) clearly illustrated the importance of absorption crossbreeding, noting that when breeding the famous thoroughbred riding breed of horses in the first stages of work, they resorted to absorbing the blood of a local English horse with the blood of horses of several eastern breeds. In the same way, Merino sheep were obtained in many states, and in the south of Russia, astra sheep (from Karakul), the American trotter (from race horses), breeds of some American and German pigs (from English breeds), many breeds of large cattle in Europe and America (from the Dutch, Simmental, Swiss, Jersey, Ayrshire and Shorthorn breeds).
On the importance of absorption crossbreeding for the transformation of animal husbandry in our country IT. D. Potemkin wrote back in 1926 in his work “Massive improvement of Russian cattle breeding (excluding Siberia and the Caucasus)”. Many tens of millions of heads of unproductive outbred cattle, sheep, pigs and other animals were transformed in our country into pedigree animals of various bloodlines in a relatively short period.
A well-organized breeding system in our country serves as a solid basis for the mass improvement of the breed composition of animals.
In those farms where the pedigree of animals is still low, it is necessary to achieve their transformation into purebreds by absorption crossing.
Introductory crossing (blood flow). They resort to it if the existing breed meets the basic requirements in terms of its qualities, but needs to improve individual features.
The breed of animals in such a crossing is determined by the breed being improved as follows: the first generation includes the offspring obtained by crossing the original animals with the producers of the breed chosen as the improving one; to the second - offspring obtained by crossing crossbreeds of the first generation with purebred animals of the improved breed (backcrossing); for purebred animals - offspring obtained as a result of crossing crossbreeds of the second generation with producers of an improving breed, subject to the severity of the desired type.
Tasks and technique of crossing. During introductory crossing, the sires of the improving breed are used once on the queens of the improved breed to obtain first-generation crossbreeds, which are mated with the best animals of the improved breed. Thus, the basic qualities of the animals of the original breed are preserved.
The main stages of introductory crossing. The first stage of blood infusion consists in crossing the queens of a slow-growing breed with sires of another breed, the qualities of which the breeder must “infuse” into the animals of the improved breed. In this case, the correct choice of the breed is of decisive importance, the features of which are transmitted to the queens through the manufacturer. It is also important that the improving rein goes well with the one being improved.
In order to improve, for example, in terms of milk productivity, milk fat content, precocity, exterior and constitutional indicators, it is introductory crossed with animals related to red , red swedish and some . To increase milk production, he is given the blood of animals of a related Montbeliard (from France) breed; to increase fat content - animal blood.
At the second stage, crossbreeds of the first generation are crossed with purebred animals of the original (improved) breed. The main task during this period is to select for further breeding animals of the most desirable type with well-defined selectable traits.
The third stage is the transition to breeding hybrids "in itself". According to the main constitutional features, crossbred animals are very close to animals of the main (improved) breed.
Conditions for successful introductory crossing. Along with the correct choice of an improving breed and the general direction in breeding, when the qualities of animals of related breeds are used to improve the initial breeds, it is important to take into account those qualities that favor the use of modern technology in animal husbandry. In such cases, it is more expedient to resort to "blood rush" and unrelated breeds. So, in order to increase the milk production of animals of some domestic breeds, improve the shape of the udder and increase the rate of milk flow, they resort to introductory crossing with the producers of the Ayrshire breed. The results thus obtained testify to the expediency of such an approach.
The success of introductory crossing also depends on the provision of farms with feed, as well as on the conditions of keeping animals and the organization of zootechnical accounting.
The experience of our country and foreign countries confirms the high efficiency of introductory crossing. It is used to increase the milk fat content of cows, improve the meat qualities of animals of various species, and in other cases.
In the farm "Askania-Nova" in the Kherson region, for example, a long-term work is underway to increase productivity and give the animals of this breed a milk-meat type, for which they are "blooded" with a milk-meat type. As a result of many years of work in Askania-Nova, a herd of animals of a new milk and meat type has been created.
Crossbreeds with milk yield and fat content of milk approach cows, and surpass the latter in live weight; they differ in precocity to a higher slaughter yield with better meat quality and lower feed consumption per unit of production. Bulls of a new type are used for breeding purposes.
Positive results have also been obtained with the improvement of black-and-white cattle with jerseys. So, in the USA, as a result of crossing Holstein-Friesian cattle with Jersey bulls, crossbreeds of the second generation of the Jersey breed were obtained, the milk fat content of which is 4.12-4.4% .
Currently, introductory crossing is quite widely used in breeding work.
Reproductive (factory) crossing. With this breeding method, animals of two (simple) or more (complex) breeds are used to produce offspring that combine their positive features. When creating new breeds of hybrids that meet the requirements for them, they are bred "in themselves", that is, hybrid queens are covered by hybrid producers. Reproductive crossbreeding has created many breeds of farm animals that are distinguished by rather high productive qualities and are well adapted to their living conditions.
Yes, sheep Altai breed, slightly inferior in productivity Ascanian, surpass them in greater compliance with their constitution to the natural conditions of the Altai Territory.
Reproductive crossing requires the involvement of a large number of animals; the eye is much more difficult than other breeding methods. In this case, not only a combination of the qualities of the original breeds in crossbreeds is achieved, but also the development of new desirable features in animals. Most often, an aboriginal breed is used as a mother, the animals of which are well adapted to local conditions; other breeds (one or more) are selected taking into account the individual and breed characteristics of animals so that they can make up for the missing qualities of the local (aboriginal) breed. The more differences in the crossed breeds, the more diverse the crossbreeds; among them it is easier to identify individuals with completely new qualities. However, it is much more difficult in such cases to fix the desired qualities in the offspring. On the contrary, the greater the similarity between the crossed breeds, the relatively easier it is to consolidate similar qualities in the offspring.
In each breed there are different variants of intrabreed types, so the choice for crossing the appropriate breeds also involves careful selection of individuals according to the desired characteristics. In such cases, individual selection, selection, evaluation of producers in terms of the quality of the offspring are required.
At the final stage of work on the breeding of a new breed by reproductive crossing, hybrid queens that meet the desired requirements and combine the valuable qualities of the original breeds are mated with hybrid producers of the same quality and origin, that is, they resort to breeding them “in themselves”. If necessary, the blood of animals of other or original breeds can be "fused" to the crossbreeds, which is called corrective crossbreeding.
Methods of breeding new breeds.
A. I. Ovsyannikov, summing up the methods of breeding new breeds by reproductive crossing, gives the following sequence of work:
- development of a new breed model (excellence standard). Determine the type of physique and the main economically useful features of animals of the future breed, taking into account its adaptation to climatic, economic conditions, as well as the ability to satisfy national economic needs;
- selection of source material. The initial breeds are selected (the animals of at least one of the crossed breeds must differ in the qualities that the hybrids are planned to have), the animals are evaluated and selected for crossing, and, finally, the farm is selected;
- genetic enrichment of crossbreeds according to the desired
qualities, breeding crosses "in itself", for which it is important to create favorable conditions for feeding and keeping. If the animals obtained during the first crossing do not satisfy the breeder, one or two backcrosses are carried out on the improving breed or representatives of the new factory breed are used for this; - when crossing, they necessarily resort to strict rejection of hybrids that do not meet the desired requirements, as well as to related mating of the best producers and queens.
To consolidate the desired qualities in the crossbred offspring, an individual selection of animals is used with a thorough justification of its purpose. Reliable results in such cases are given by inbreeding, which is combined with unrelated mating, for which animals are selected that are similar in type to inbred ones. To avoid too close inbreeding and to consolidate the necessary economically useful qualities in the offspring, several lines and uterine families are laid. With a strong deviation of the crosses in the undesirable direction, they are mated with animals of the desired type, and sometimes with producers of one or more original breeds. Crossbreeds "in themselves" are bred only when they meet the desired requirements.
Simple and complex reproductive crossing. Reproductive crossing can be simple or complex. In the first case, animals of two breeds participate in crossing, in the complex case - three or more breeds. Most breeds of cattle are created as a result of simple reproductive crossing using local cattle and animals of any factory breed.
FROM M. F. Ivanov used reproductive crossing to breed new breeds of farm animals with great efficiency. In a short time, he created a domestic Ukrainian steppe white breed pigs, a highly productive Askanian breed of fine-fleeced sheep, and began work on the creation of a mountain merino. The main stages in the breeding of new breeds of sheep by reproductive crossing are obtaining hybrids (hybrids) of a certain bloodline, their enhanced rejection, the use of inbreeding and constant selection work with animals. As a starting material, M.F. Ivanov selected, as far as possible, homogeneous animals of a strong constitution, which he crossed with highly productive producers of factory breeds also of a strong constitution. When obtaining crossbreeds of a certain bloodline, in order to consolidate desirable qualities in the offspring, he resorted to inbreeding, and in this case he used only outstanding producers. In addition, M.F. Ivanov used a very strict culling of animals that did not meet the desired requirements, as well as weak, sick, pampered, backward in development, with deformities and other defects. He paid great attention to the formation of several unrelated lines, so that after obtaining more or less homogeneous genotypes, it would be possible to start unrelated mating and create favorable conditions for feeding and keeping hybrid animals, especially young animals.
Similar methods were used in the breeding of the Ukrainian steppe white breed of pigs.
As a result of complex reproductive crossing, the Kostroma breed of cattle was also created. At the same time, purebred and crossbred bulls of the Algauz and Swiss breeds, Yaroslavl, Miskovsky and local outbred cattle were used.
When breeding Soviet Merino sheep by complex reproductive crossing, local coarse-wooled sheep from various regions of the country, Merino rams and dams of the Mazaev and Novokavkaz breeds, American rambouillet rams and new domestic fine-fleeced breeds - Askanian, Caucasian, Altai, Stavropol, Grozny, etc.
By crossing local Kuban pigs with animals of large white, Berkshire and white short-eared breeds on collective farms and state farms of the Rostov region and the Krasnodar Territory, the North Caucasian breed of pigs was created.
In horse breeding, by complex reproductive crossing using mares of the Don and Black Sea breeds and thoroughbred riding stallions, the Budennovskaya horse breed was created, combining the best qualities of the Don and thoroughbred riding breeds.
The value of reproductive crossing lies in the fact that it allows you to create completely new breeds with predetermined parameters of economically useful and biological qualities. The involvement of several breeds in this type of crossbreeding, the selection for a combination of desirable traits, makes it possible to sharply increase the economic value of new breeds and adapt them to the technology of industrial animal husbandry.
All countries of the world with intensive animal husbandry are working to create new breeds by the method of reproductive crossing.
Industrial crossing. It is used in all branches of animal husbandry to put into practice the effect of heterosis. It is widely used in modern non-breeding farms of an industrial type. When using animals of two breeds, crossing will be simple, and three or more breeds will be difficult. The main purpose of industrial crossbreeding is to create highly productive user herds.
In many cattle breeding farms, especially in European countries and America, dairy and dairy-beef cows of less value in breeding terms, the young of which are grown for meat, are inseminated with the sperm of bulls of early maturing beef breeds. At the same time, the production direction of the economy does not change, since cows are used to produce milk, and non-breeding crossbred young animals serve as material for the production of high-quality meat. Industrial crossbreeding is also widely used in pig breeding to produce first-generation crossbreeds.
An important conditional application of this breeding method in all branches of animal husbandry is the presence of not only producers, but also purebred queens of a certain breed. The use of hybrids of unknown origin in such crossing does not always provide the expected effect. In a number of branches of animal husbandry, in particular in sheep breeding, the effect of heterosis during industrial crossing is also achieved with a more complex combination of breeds.
In some countries, complex industrial crossbreeding is carried out on farms that are not the same in terms of the intensity of animal husbandry and natural and climatic conditions.
For example, in the sheep farms of England, located in the mountainous regions of extensive sheep breeding, local queens are crossed with rams of the long-haired meat-and-wool Border Leicester breed. Crossbreeds of the first generation of rams are then castrated and, after fattening, sent for slaughter, and crossbred ewes are sold to farmers in lowland areas, where forage conditions are better than in the mountains. Here, these ewes are crossed with rams of more early maturing short-haired breeds (Oxfordshire, Southdown, etc.). The offspring resulting from such crossing is completely slaughtered.
In poultry farming, industrial crossbreeding is widely used to obtain the so-called hybrid bird, which is superior in productivity to the bird of the original breeds (lines). In many countries, this breeding method is also used in horse breeding in order to obtain half-breed horses, mainly for sports purposes.
The economic efficiency of industrial crossbreeding is obvious, since, compared with peers of the parent breed used in this case, the crossbreeds differ the best development and higher productivity.
The use of industrial crossing in beef cattle breeding provides rapid increase production of high quality beef. Good results are obtained when using bulls of the breed Charolais and Kian.
A great economic effect in pig and poultry production is provided by the method of interline hybridization, which is a high form of industrial crossing and is widely used during the transition to the production of livestock products on an industrial basis. Interline hybridization may include forms when animals of two matching lines of one or more breeds are crossed. Other forms of interline hybridization are also known.
The efficiency of the production of interline hybrids can be judged from the following data. On international markets, hybrid fastback pigs, saike, cotswold (Great Britain), spurs (Holland), animals bred by Farmer Hybrid (USA), etc. are widely used. Hybrid pigs cotswold are very prolific: under average conditions, they bring 21 piglet. Young growth at 8 weeks of age weighs 20 kg, at 160 days old - 90 kg; feed costs per 1 kg of live weight gain - 2.62 kg.
In the Canadian poultry industry, the Shaver 288 crosses were recognized as the best egg hybrid crosses in 1973 (average egg production 249.5 eggs, feed costs per 1 kg of egg mass 2.47 kg). "Babcock 305" (respectively 277.4 eggs and 2.51 kg), "Babcock 300" (240.6 eggs and 2.48 kg). Hybrids are widely used in the production of broilers.
Interline hybridization is also used in sheep breeding.
In the UK, for example, on the basis of the Dorsethorn and Finnish Landrace breeds, hybrid sheep improver Kadzova were created. From every 100 queens - crossbreeds of Scottish black-faced sheep with these hybrids - 222 lambs are obtained per year, and from 100 hybrids of nmproper X Dorset Horn - 233 lambs.
Heterosis effect- a complex biological phenomenon, depending on the genetic capabilities of the original breeds or lines, the heterozygous structure of the genotype, the maternal effect and the living conditions of both the offspring and parents.
The higher the productivity of animals of the original breeds, the higher the productivity of hybrids obtained as a result of industrial crossing. Therefore, the choice of breeds for crossing is crucial. Many experiments have been carried out to determine the best combinations various breeds. In beef cattle breeding, more than 50 variants of various combinations of dairy breeds and double productivity with meat, as well as beef breeds among themselves, have been studied. Similar studies have been carried out in other branches of animal husbandry. The most promising combinations of breeds for industrial crossing have been developed, which are being introduced into production. In beef cattle breeding, it is recommended, for example, to use: producers of the Hereford breed and cows of the Red Steppe, Simmental and Black-and-White; breeders of Aberdeen Angus (large type), Santa Gertrude, Charolais and Red Steppe cows; bulls of gray Ukrainian, Simmental breeds and black-and-white cows; shorthorn producers (large meat and milk-meat type) and red steppe cows.
Crossbred young animals of the farm are sold for meat at the age of 15-18 months after intensive rearing and fattening.
A distinction is made between simple industrial crossing, in which animals of two breeds are used (Fig. 16), and complex, when individuals of three breeds are mated sequentially. The complex industrial crossing shown in the second scheme is used, in particular, in the GDR in order to improve the milk and milk fat content of Black-and-White breed animals. With this combination of breeds, hybrids are obtained that are distinguished by the best indicators of udder development, fertility and productivity.
The uterine composition for industrial crossing is used, as a rule, of the breed that is well adapted to local conditions. Manufacturers are selected taking into account previously identified compatibility, and they are subject to higher requirements than queens. It is desirable that both queens and sires be purebred. In simple industrial crossbreeding, crossbreeds of the first generation are used to obtain products, while in complex crossbreeding, they are crossed with animals of one or more breeds. Only after that, complex crossbreeds are obtained that meet the goals of user animal husbandry.
Industrial crossing on farms is organized on separate farms, in herds, isolated from breeding material. At the same time, they create good conditions for feeding and keeping and keep a thorough zootechnical record. Crossbreeds obtained as a result of industrial crossing for breeding purposes are usually not used.
A type of industrial crossing is variable (rotational) crossing , in which the queens of the original (then crossbred) group are mated alternately with producers of two or more breeds. As a result of rotational crossing, the effect of heterosis is continuously maintained, which ensures effective use crossbreeds for the production of milk, meat, eggs and other livestock products. Variable crossing is especially effective in pig breeding, beef cattle breeding and poultry farming.
It is more difficult to organize rotational crossing than industrial crossing, but its economic effect is higher.
Sometimes the use of variable crossbreeding ends with the breeding of a new breed.
In particular, in France, crossbreeds of English riding and Norman draft horses were crossed alternately with English and Norman stallions. At a certain stage, they switched to breeding hybrids “in themselves”. As a result, the work ended with the breeding of the Anglo-Norman breed of horses.
When choosing breeds for crossing and determining the degree of use of each of them, they proceed from the goals set. The selection of breeds and the sequence of their crossing must be previously studied in the experiment. When animals of two breeds are used for mating, variable crossing is called simple, and three and more breeds - complex. Crossbreeds of the first generation, obtained as a result of two-breed crossing, are mated with producers of one of the original breeds, crossbreeds of the second generation - with producers of another original breed; in the next generation, backcrossing is carried out, etc.
In a three-breed alternating crossing, hybrid queens obtained as a result of mating animals of two breeds (AxB) are covered by producers of a third breed (C). Their offspring are bred to breed A sires, the next generation offspring to breed B sires, and their offspring to breed C sires, and so on. In the case of using four breeds, the crossbred breeding stock is mated alternately with sires of each of the four breeds.
The use of several breeds in rotational crossing makes it possible to obtain a combinative combination of traits in crossbred animals.
Hybridization
Hybridization is the crossing of animals belonging to different species. The resulting offspring are called hybrids. Hybridization as a breeding method also includes the crossing of hybrids with hybrids of different and identical origin. The main task of this very difficult method of crossing is the involvement of new valuable wild and semi-wild forms of animals into the material culture of man. Depending on the ability or inability of hybrids to produce offspring, a distinction is made between hybridization, which is widespread and produces useful animals (for example, mules in the past), and hybridization, which is used to create new breeds and types of animals. In this regard, four types of animal hybridization are distinguished: industrial, absorption, introductory and reproductive. The most widespread industrial (user) hybridization and reproductive, or breed-forming.
It should be noted that wild fauna (huge natural wealth) is unreasonably, and sometimes predatory, exterminated. In the last 50 years alone, more than 40 animal species have been destroyed. Species such as zebra quagas in Africa, American bison, tour, tarpan, arctic penguins, gigantic flightless geese, dodos - fat big island birds, moa ostriches, whose weight was 300 kg, height 4 m, died out or exterminated. To prevent the extinction of wild animals, special measures are now being taken to protect nature. In 1948 was created international union nature conservation. In the USSR in 1978 a special Law of the USSR on Nature Protection was issued. More than 350 species of animals and 650 species of birds live on the territory of our country. Among many reserves of the country there are such large scientific centers as Askania-Nova, Astrakhan, Belovezhskaya Pushcha, Laplandsky, Caucasian, Issyk-Kulsky, etc. They do a lot of work on animal hybridization and conservation of valuable species of wild fauna.
When hybridizing animals, they face great difficulties. The main ones are the following:
1) non-crossing of species among themselves;
2) partial or complete sterility of hybrids.
The main reasons for the non-crossing of distant species and the infertility of hybrids are genetic factors: a different set and structure of chromosomes in gametes, their inability to form a viable zygote, sperm, due to its morphological and biochemical characteristics, is not able to lyse the shell of a foreign egg, to penetrate into it. If a hybrid zygote is formed, then due to embryonic pathology, either the resorption of the fetus occurs in the early stages of formation, or its death. This is explained by the fact that the body's immune protective bodies fight the penetrating foreign protein, destroying it. Due to the genetic differences of the parents in hybrids, the formation of male and female germ cells is disrupted and they become infertile. The sterility of the hybrids is caused by abnormalities in the development of the gonads and mitosis.
Rapid development Nowadays, cytogenetics has made it possible to study in more detail the cytogenetic causes of infertility in hybrids. They can be divided into three groups:
a) discrepancy in the number of chromosomes in the karyotype;
b) morphological structural differences in the structure of chromosomes;
c) a change in the gene composition that does not affect the behavior of chromosomes, their morphology.
Currently, scientists have developed a number of methods to overcome the non-crossing of individual species. These include: blood transfusion of animals of one species to another, mixing of sperm of individuals of different species, the use of reciprocal (back) crossing, hormonal preparations, the use of special sperm diluents, transplantation of gonads, and the creation of the necessary conditions for obtaining and raising offspring. Experiments have shown that young females more often give hybrid offspring: a greater ability to hybridize and give birth to fertile offspring is observed in those individuals that themselves are obtained as a result of crossing.
It has been established that in cases where there are gender differences in the manifestation of sterility or viability of hybrids, they appear more often in the heterogametic sex of hybrid males (y) than in the homogametic female (xx) sex. Obviously, this phenomenon is affected by cytoplasmic heredity and the maternal effect in the inheritance of traits, which can be used in the selection of pairs for crossing, taking into account the sex of the parents (reciprocal selection). We have indicated only the main methods and means of overcoming the non-crossing of distant species and the infertility of hybrids. The rapid development of genetics, molecular biology, biotechnology, genetic and cell engineering in our days, apparently, will allow in the near future to completely solve the problem of infertility in the distant hybridization of animals.
Most promising methods to solve this problem, one can consider genetic and cellular engineering, hybridization of somatic cells (ultrahybridization), experimental polyploidy, etc. By hybridization of somatic cells in tissue culture, it was possible to transplant embryonic somatic cells of cattle and northern mink. Hybridization of cells is practically done as follows: unrelated cells of two organisms, the useful qualities of which it is desirable to combine when crossing, are cultivated on an artificial nutrient medium, then the culture is mixed. Under certain conditions, some of the cells merge. So far, the process of formation of hybrid systems from cells is chaotic. However, with the improvement of this method, it should be expected that somatic hybridization of cells in tissue culture will be used as an experimental model of interspecific hybridization of animals.
Promising new methods for overcoming infertility during hybridization of animals include damage to chromosomes by physical and chemical mutagens, as well as the use of microdoses of biologically active compounds of supermutagens. Special meaning acquire methods of biotechnology, obtaining transgenic animals, chimeras, cloning the genotype of valuable animals.
The most ancient form of hybridization is crossing horses With donkey and getting mule. Even in ancient Rome, mule breeding was widely developed. The mule is an excellent pack animal, unrivaled in endurance, longevity and efficiency. It is obtained by crossing a donkey and a horse; when a donkey is mated with a stallion, a hinny will be born. The mule is larger and more valuable than the horse, but is generally sterile. Breeding these animals "in itself" is impossible.
In our country, in Askania-Nova, great work Of some interest is the hybridization of a horse with zebras and the production of strong hardy zebroids, as well as the crossing of a domestic horse and its wild ancestor, the Przewalski horse. Males from such crossing are sterile, and females are fertile. According to E. P. Steklenev, these species show differences in the karyotype (the number of chromosomes in the domestic horse is 64, in the Przewalski's horse 66), as well as features of gametogenesis. In hybrid infertile males, despite the completeness of gametogenesis, there is a difference in the size of germ cells, their degeneration, rejection at different stages of formation, as well as asymmetry in the location of the testes, their underdevelopment. In hybrid females aged from one to 10 years, generative processes, sexual cyclicity, conception and fetal development occur normally.
Hybridization is also used to create new breeds of farm animals. Many farms have studied such issues as the selection and selection of pairs, the biological characteristics of zebu-like cattle, their adaptability to local conditions, etc. It has been established that hybrids are resistant to piroplasmosis, inherit increased milk fat and protein from zebu, and are responsive to improved feeding and keeping conditions. , pay well for food, have excellent meat qualities. The meat contains an increased amount of fat and protein, the slaughter yield reaches 60%. Udder disease is less common gastrointestinal tract, hooves. It is also important that hybrids obtained by crossing cattle with zebu are fertile.
In connection with the concentration and intensification of animal husbandry in all climatic zones of the USSR, the hybridization of cattle of factory breeds with zebu makes it possible to create dairy and meat breeds livestock that meet the requirements of the new (industrial) technology of the industry. Of great interest are the works carried out in the scientific and experimental farm "Snigiri". Here the zebu was crossed with black-and-white cattle, which made it possible to obtain highly productive hybrids with a milk yield of 3997 kg and a milk fat content of 4.27%. In the Central Asian republics, there are breed groups bred on the basis of crossing zebu with Swiss and East Frisian cattle. The milk yield of such hybrids is 10-15%, and the fat content of milk is 20-25% higher than that of purebred animals.
Of great interest are the works on hybridization of cattle with banteng, carried out in Askania-Nova. Hybrids from crossing banteng with red steppe cattle are characterized by excellent meat qualities, pronounced heterosis. Milk yield of hybrid cows was 1500-2200 kg, milk fat content was 6.1%. Rich material has been accumulated in the works of A. E. Mokeev and P. N. Buina on three-breed crossing (Santa Gertrude x Webu x Red Steppe breed; Shorthorn Zebu x Red Steppe breed). Availability
zebu blood in both variants of crossing gave excellent results. A new type of beef cattle has been created.
The hybridization of the yak with Simmental cattle in the conditions of the high mountain regions of Altai and the Kirghiz SSR is of great national economic importance. Yak hybrids with Simmental cattle are distinguished by good milk production, high fat content of milk (5.5-7), adaptability to breeding in high-mountain alpine pastures. Thanks to these hybrid forms, cattle breeding is becoming widespread in the mountainous regions of the country.
For hybridization, bison are also used, of which there are only a few hundred worldwide. Now the number of bison is being restored. Of considerable economic interest are hybrids of cattle and bison. As a result of 15 years of work, cattle breeder D. Bissolo from California managed to cross Charolais and Hereford cows with wild American bison. The new breed group was named bifalo. The hybrid offspring, which has 3/8 of the blood of a wild bison, 3/8 of the Charolais and 3/4 of the blood of the Herefords, is characterized by high precocity (weighs 400 kg at 10 months of age), well-developed meat forms. Data laboratory research showed that the meat of such hybrids contains 18-20 protein and only 7 fat. The main type of food for bifalo hybrid animals, according to D. Bissolo, is pasture grass. They are hardy, have a high resistance to many diseases common in hot climates.
Hybrids have also been obtained from crossing cattle with gayals and African Watusi cattle. A very promising species for distant hybridization is the African eland. This is a very large species of antelope: males weigh 700 kg, females - 540-500 kg. Females give milk well, milk yield per lactation does not exceed 700 kg, but the fat content of milk reaches 10-14. The milk of eland antelopes has healing and bactericidal properties. Yogurt from this milk does not spoil for many years under normal conditions. Now methods have been developed for obtaining sperm from eland males on the vagina and artificial insemination of cows is being carried out in order to obtain hybrid forms.
A lot of work is being done in Askania-Nova and in a number of other reserves of the country to create new breeds of deer. As a result of long-term complex intraspecific hybridization, the Ascanian deer breed was bred. European maral deer, Crimean and Caucasian deer and wapiti (the largest steppe deer) participated in its creation. Much has already been done to domesticate antler deer and elk.
M. F. Ivanov developed and was the first to apply the method of distant hybridization in the creation of fine-fleeced breeds of sheep. By crossing a wild mouflon ram with a fine-fleeced sheep, he received a new breed of fine-fleeced sheep - mountain merino. Animals of this breed inherited from the wild mouflon the ability to move quickly, overcoming long distances, to live in high mountains, to use alpine pastures, and from the rambouillet - the valuable productive qualities of a fine-fleeced sheep. By the method of distant hybridization in the mountains of Kazakhstan, Soviet scientists have bred the fine-wooled breed of archaromerinos.
Of great scientific and practical interest are the works of N. Gigineishvili on breeding gray karakul sheep by hybridization with wild and mountain sheep, on hybridization of sheep and goats, rabbits and hares, llamas and camels.
Remote hybridization in poultry farming gained wide scope, 96 species of birds belonging to 13 orders produced fertile offspring. Of greatest interest are hybrids of an ordinary pheasant with a wild Caucasian (Askanian pheasant), hybrids of a domestic duck with musky ducks (mulards), chicken and peacock, guinea fowl and pheasant, turkey and guinea fowl, and many others that have excellent fattening qualities. Work on remote hybridization of poultry is being successfully carried out both in the Astrakhan Reserve and in other scientific institutions of the country.
An important direction in increasing the genetic potential of pigs when transferring the industry to industrial technology is distant hybridization, the use of the gene pool of wild forms. At present, only the use of hybrids can provide an accelerated growth in the productivity of industrial pig breeding. Taking into account this situation, 19 hybrid pig breeding centers are being created in the country. Hybridization ensures the manifestation of the heterosis effect.
In the context of the intensification of pig breeding, a new direction in hybridization has appeared. The scientific substantiation of hybridization in pig breeding is based on the relatively independent inheritance of reproductive, fattening and meat qualities in pigs. This allows you to create specialized paternal and maternal forms that are successfully used in parent and grandparent herds for crossing.
In most countries of the world, in order to intensify pig breeding, create new highly productive types and breeds, long-term programs for hybridization in pig breeding have been developed and are being implemented.
Heterosis and its importance in animal husbandry
Heterosis (from Greek heteroiosis - change, transformation). Heterosis is understood as the superiority of the offspring of the first generation over the parental forms in terms of viability, endurance, growth energy, fertility, constitutional strength, resistance to diseases, which occurs when different races, animal breeds, and zonal types are crossed.
The term "heterosis" was introduced by G. Schell (1914), who explained the presence of "hybrid strength" by the state of heterozygosity in the genotype of an organism, which is formed as a result of crossing. The hypothesis of heterosis, formulated by G. Schell, E. East, H. Hayes, explains the phenomenon of heterosis by the presence of heterozygosity of various loci and the overdomaining that manifests itself, that is, when the effect of heterozygote Aa on the manifestation of the phenotype is stronger than that of the homozygous dominant genotype AA (that is, the effect of the action of Aa is greater than the action of AA).
Another explanation of heterosis, formulated by Kiibl and Pellew (1910), is based on the fact that when organisms carrying different homozygous genes in the genotype, such as AAbb and aaBB, are crossed, the recessive alleles in the crossbred offspring pass into the heterozygous form of the AaBv genotype, in which the harmful effect is eliminated. recessive genes. The influence of dominant genes on the manifestation of heterosis can be explained by a simple cumulative effect of a large number of dominant genes, that is, there is an additive effect.
A. Shell and O. East proposed a hypothesis of overdominance, which is close to the hypothesis of obligate heterozygosity put forward by D. A. Kislovskiy. Its essence lies in the fact that high heterozygosity is better than homozygosity provides a variety and enhancement of the physiological functions of the body. H.F. Kushner, based on a large number of experiments, identified five forms of manifestation of heterosis used in animal husbandry:
- hybrids (or crossbreeds of the 1st generation surpass their parents in live weight and viability;
- crossbreeds of the first generation surpass their parents in constitutional strength, longevity, physical performance with complete or partial loss of fertility;
- crossbreeds of the 1st generation in terms of live weight occupy an intermediate position, noticeably surpass their parents in terms of multiple pregnancies and viability;
- each individual feature behaves according to an intermediate type
inheritance, and in relation to the final product there is an increased
heterosis; - crossbreeds, or hybrids, do not exceed the best parental form in terms of productivity, but have a higher level of productivity compared to the arithmetic mean of both parents.
The classic example of heterosis is the mule, a hybrid between a donkey and a horse. These are strong, hardy animals that can be used in much more difficult conditions than parental forms.
Modern ideas about the causes of heterosis are based on the fact that heterosis is the result of the interaction of many genes. Their multiple action leads to the heterosis effect. This explanation is called balance heterosis. Subsequently, Lerner and Turbin continued to develop this provision.
According to them, heterosis is due to the action of many genes mutually balanced in the genome in the process of evolution, which determines the optimal development and adaptability of the organism to environmental conditions.
If during crossing the optimal genomes of both parents combine, then the descendants of the first generation have the most favorable situation in the combination of genomes, which leads to the appearance of heterosis. Consequently, heterozygosity accompanying crossing undergoes the pressure of various factors and thus creates a balanced interaction of genes in the genome.
In the practice of animal husbandry, the so-called negative heterosis is sometimes observed, when the offspring have a trait level below the average of the parents, but slightly higher than the level of the trait of the parent in which it is less developed. The higher the differences in the trait level of the parental forms, the more the average trait level of the descendants approaches the trait level of the worst parent. This feature in inheritance was described by Ya.L. The wool shearing of the first generation crossbreeds was somewhat greater than that of the Angora goats, in which it was 4-5 times greater than that of the coarse-haired and local goats.
Modern animal husbandry is characterized by the use of crossbreeding, accompanied by a heterotic effect, especially for egg and broiler poultry farming. This system includes two main stages: the breeding of inbreeding lines of birds using different types of inbreeding and crossing (crossing) lines to obtain the so-called hybrid birds, which show heterosis. For example, in the Netherlands, Eurybrid works with two crosses of egg-oriented chickens: Highsex White (white shell based on leghorns) and Highsex Brown (with the participation of Rhode Island and Newhamshire with brown shells. These two crosses occupy a leading position in the global poultry industry.
Work on the creation of a hybrid egg and meat poultry is carried out in our country. To carry out selection for obtaining heterosis, inbred lines are bred by mating according to the “brother x sister” type for 3-4 generations or more, combining this with a strict culling of unwanted individuals. Of the larger number of laid lines, about 10-15% of the lines remain for the final, with an average inbreeding coefficient of 37.5% (mating of full siblings for three generations). Next, the remaining lines are crossed with each other to check for compatibility, then the most successful combinations are left for production crossing and 2-, 3-, 4-line hybrids are obtained.
The use of the effect of heterosis is also used in work with other animal species, especially in beef cattle breeding, sheep breeding, camel breeding, and fish farming. Methods for obtaining the effect of heterosis are varied. Heterosis is manifested in interspecific crossing of animals: obtaining mules from crossing a donkey with a mare, breeding new heterotic breeds by obtaining hybrids from crossing cattle with zebu (Santa Gertrude, Beefmaster, Charbray, Bridford in the USA; Sao Paulo - Brazil, haupgamitin - in Jamaica). In our country, distant hybridization has been carried out between fine-fleeced sheep and argali, and a new breed has been bred - arharomerinos. In Kyrgyzstan and Altai, hybrids of yak with Simmental cattle have been obtained. Heterosis in interbreeding. In the zootechnical literature, there are most examples of the appearance of heterosis in animals of different species when interbreeding is not used.
In beef cattle breeding, when crossing some breeds, crossbreeds of the first generation surpass the original breeds in terms of fattening quality in live weight at different age periods.
In dairy cattle breeding, heterosis in terms of milk yield and fat content in milk during interbreeding is rarely observed. Data on heterosis in terms of milk yield are given by N.F. Rostovtsev from the experience of crossing Ostofrisian cows with bulls of the Red Gorbatov breed. In dairy cattle, the effect of heterosis is observed more often in terms of the total amount of milk fat per lactation, especially when crossing cows of different breeds with bulls of the Jere breed.
In pig breeding, interbreeding industrial crossbreeding is used more widely. Scientific institutions of our country have experimentally tested more than 100 variants of industrial crossbreeding of pigs. In many cases, the effect of heterosis has been established. Basically, it manifested itself in an increase in fertility, the viability of the offspring, and an improvement in its fattening qualities. In the experiments of M.A. Selekh crosses from crossing queens of large white breed with Berkshire boars spent feed per 1 kg of live weight gain per 0.5 -1 feed. units less than the original purebred animals.
According to M.A. Zhabaliev hybrids (Landrace x Large Black) consumed 4.1 feed units per 1 kg of growth, while purebred Landrace and Large Black pigs consumed 4.2 and 5.08 feed units, respectively. units In the experiments of I.E. Zhirnov, crossbreeds from crossing pigs of Large White and Estonian breeds gave 600 g of average daily gain in live weight when fed, and the original breeds, respectively, 548 and 560 g. According to V.O. Chetyrkin, higher gains and better feed payment compared to the original breeds the crosses differed from the crossing of the queens of the large white breed and the boars of the Moldavian black breed group. The average daily gain in live weight was 598 g, the cost of feed per 1 kg of gain was 4.0 cor.un. Moldovan - 394 and 4.3%.
In addition to egg production, with interbreeding of chickens, heterosis is expressed in increased embryonic and postembryonic viability, in growth energy, improved meat quality and feed payment.
To obtain heterosis in interbreeding great importance has the correct selection of paternal and maternal breeds, as well as the choice of breed representatives. In poultry farming, as N.F. Rostovtsev, where there is a rapid change of generations and there is a great opportunity for selection, methods have been developed for the directed formation of the heredity of the original crossed forms, which ensure the appearance of heterosis in their crossbred offspring.
Heterosis using heterogeneous selection in intrabreed mating. The use of lines, lines of producers and families in purebred breeding, as well as the mating of animals belonging to the same breed grown under different conditions, are also options for heterogeneous selection. Heterosis using heterogeneous selection during intrabreed mating, in which the mated animals are in the same household, do not have a clear linear affiliation or belong to the same related group and therefore are related to each other to one degree or another. Such heterogeneity is most often expressed in the difference between mated individuals only in some respects, in particular, in conformation-constitutional features.
The problem of obtaining and enhancing the effect of heterosis has not been fully resolved. The main indefinite obstacle is the loss of the heterosis effect in the second generation, that is, the heterosis obtained in the first generation is not fixed, but is lost in subsequent generations when breeding crosses “in itself”. Some methods allow you to maintain heterosis in several generations. One of the most accessible and effective methods is variable crossbreeding, which is used in consumer (commercial) animal husbandry. At the same time, from the crossbreeds of the first generation obtained from crossing the queens of breed A with the producers of breed B, the best part of the queens is isolated and crossed with the producer of breed C, a crossbreed of the second generation is obtained, with the manifestation of heterosis when three breeds are combined (A, B, C) Further crossbreeds of the second generation can be crossed with the producer of the breed D and get more complex crossbreeds in which the heredity of the original maternal breed A and the heredity of the paternal breeds B, c and D are presented. Other methods to preserve the effect of heterosis have not been developed in animal husbandry.
In the practice of modern animal husbandry, it has been proven that the effect of heterosis is diverse and is expressed in the improvement of valuable economic traits. The main indicators of heterosis are an increase in embryonic and postembryonic viability, a decrease in feed costs per unit of production; increase in precocity, fertility, productivity; manifestation of broader opportunities for adaptation to changing conditions and new elements of technology. The wide range of the heterotic effect, manifested in the variety of reacting traits, is a reflection of the physiological and biochemical processes determined by the peculiarities of the genetic apparatus of heterotic animals.
Incredible Facts
In the fictional world, there are many strange and unusual creatures, and with the help of Photoshop you can create different non-existent animals.
All animals in this list are real.
These real hybrid animals are the result of genetic engineering, which in the future may give rise to even more exotic creatures.
Did you know about such animals as leopon, narluha or hainak?
Animal hybrids (photo)
1. Liger - a hybrid of a lion and a tigress
Ligers are the offspring of male lions and female tigresses. Although there are legends that ligers roam the wild, at the moment they exist only in captivity, where they are specially bred.
There is a misconception that ligers do not stop growing all their lives. They don't, they just grow to enormous sizes in their growth range. Ligers are the largest felines in the world. Hercules is the most big liger weighs 418 kg.
2. Tigon - a hybrid of a tiger and a lioness
The tigon or tigrolev is a hybrid of a male tiger and a female lioness. It was believed that tigons are smaller than their parents, but in fact, they reach the same size, but they are smaller than ligers.
Both ligers and tigers are able to produce their offspring, which leads to the birth of hybrids such as titigons or liligers.
3. Zebroid - a hybrid of a zebra and a horse
A zebroid is a mixture of a zebra and other equines. Zebroids have existed for a long time, they were mentioned in Darwin's notes. As a rule, these are males with the physiology of a non-zebra parent and stripes adorning certain parts of the body.
Zebroids are more wild than pets, difficult to tame, and more aggressive than horses.
4. Coywalk - a hybrid of a coyote and a wolf
Coyotes are genetically similar to red and eastern wolves, from which they split off about 150,000 to 300,000 years ago. Interbreeding between them is not only possible, but is becoming more common as the wolf population recovers.
However, coyotes are not very compatible with gray wolves, from which they are genetically separated by 1-2 million years. Some hybrids, although they exist, are very rare.
There are different hybrids of coywolves that inhabit mainly North America. They are usually larger than coyotes, but smaller than wolves, and have characteristics of both species.
5. Grolar - a hybrid of a white and brown bear
Grolar, also called "polar grizzlies", are a hybrid of a polar bear and a brown bear. Most polar grizzlies live in the zoo, but there have been a few cases where they have been seen in the wild. In 2006, an Alaskan hunter shot and killed one.
Outwardly, they are similar to both polar and brown bears, but in behavior they are closer to polar bears.
6. Savannah - a hybrid of a domestic cat and a serval
It's amazing, but rare breed is a hybrid of domestic cats and serval - a type of wild cat living in Africa. They are very large and act like dogs, following their owners around the house, wagging their tails to show pleasure, and even playing catch.
In addition, savannahs are not afraid of water and adapt easily. However, these cats are very expensive.
Interspecific hybrids of animals
7. Killer whale - a hybrid of a killer whale and a dolphin
From the male of the little black killer whale and the female bottlenose dolphin, killer whales appear. They are extremely rare, and only one representative is known to exist in captivity.
8. Cow bison - a hybrid of a cow and a bison
A hybrid of a cow and a bison has existed since the 19th century, when they were called katalos. Cow bison are healthier than cattle and cause less environmental damage to the prairies where they graze.
Unfortunately, as a result of breeding, there are now only 4 herds of bison that do not have cow genes.
9. Loshak - a hybrid of a stallion and a donkey
In fact, a hinny is the opposite of a mule. The mule is the offspring of a donkey and a mare, and the hinny is a hybrid of a stallion and a donkey. Their head is similar to that of a horse, and they are slightly smaller than mules. Also, hinnies are less common than mules.
10. Narlukha - a hybrid of a narwhal and a beluga whale
The narwhal and the beluga whale are two members of the narwhal family, so it's not surprising that they are capable of interbreeding.
However, they are extremely rare. Recently, they have been seen more often in the eastern part Atlantic Ocean, which many consider a sign of climate change.
11. Kama - a hybrid of a camel and a llama
Kama did not exist until 1998. Some scientists at the Camel Reproduction Center in Dubai decided to cross a male dromedary with a female llama through artificial insemination, producing the first kama.
The goal was to produce wool and use the kama as a beast of burden. To date, five camel-llama hybrids have been produced.
12. Hainak or dzo - a hybrid of a cow and a yak
The zo (male) and zomo (female) are hybrids between domestic cows and wild yaks. They are mainly found in Tibet and Mongolia, where they are valued for their high yield of meat and milk. They are larger and stronger than both cows and yaks, and are often used as beasts of burden.
Animal hybrids
13. Leopon - a hybrid of a leopard and a lioness
A leopon appears from a male leopard and a lioness. This situation is almost impossible in the wild, because all leopons were raised in captivity. Leopons have the head and mane of a lion, and the body of a leopard.
14. Sheep-goat hybrid
Goats and sheep seem very similar, but they are much more different from each other than it seems at first glance. Natural hybrids between these animals are usually stillborn and extremely rare. The animal, called the goat-sheep chimera, was artificially reared from goat and sheep embryos.
15. Yaglev - a hybrid of a jaguar and a lioness
Yaglev is a hybrid of a male jaguar and a lioness. Two yagles, named Zhazhara and Tsunami, were born in the Bear Creek Wildlife Refuge in Ontario.
16. Mulard - a hybrid of wild and musky duck
Mulard is a cross between a wild duck and a Muscovy duck. The Muscovy Duck is native to South and Central America and is distinguished by bright red growths on its face. Moulards are raised for meat and foie gras, and they themselves cannot produce their offspring.
17. Zubron - a hybrid of a cow and a bison
Zubron is a hybrid of a cow and a bison. Zubrons are superior to domestic cows in many respects, as they are stronger and more resistant to disease.
They were considered as a possible replacement for cattle, but now bison remain in only one herd in Belovezhskaya Pushcha in Poland.
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MINISTRY OF AGRICULTURE
RUSSIAN FEDERATION
DEPARTMENT OF SCIENCE AND TECHNOLOGY POLICY AND EDUCATION
federal state budgetary educational institution higher professional education
SAINT PETERSBURG STATE
ACADEMY OF VETERINARY MEDICINE
Department of Genetics and Livestock
SUMMARY ON THE TOPIC:
"Interspecific hybridization"
Completed by: student of the 2nd year of the 5th group
FVM full-time learning
Fadeeva Anna Vitalievna
Introduction
Hybridization is the crossing of organisms that differ in heredity, that is, one or a large number pairs of alleles (gene states), and, consequently, one or more pairs of traits and properties. The crossing of individuals belonging to different species or even less related taxonomic categories is called distant hybridization. Hybridization is also divided into natural and artificial. The natural has been observed for a long time, for example, mules existed already two thousand years BC. e. The artificial production of hybrids was first proposed by the German scientist R. Camerarius (1694), and the first artificial hybridization was carried out by the English gardener T. Fairchild, he crossed in 1717 different types carnation. Kölreuter is considered the founder of the theory of hybridization in plants; he obtained hybrids of two types of tobacco (1760). Gregor Mendel laid the scientific foundations of genetics through his experiments on pea hybridization. Charles Darwin also made huge number hybridization experiments.
Hybridization itself includes the fusion during fertilization of genotypically different germ cells and the development of a new organism from the zygote, which combine the hereditary inclinations of the parents. In the first generation of hybrids, heterosis is characteristic, it is expressed in better adaptability, greater fecundity and viability of individuals.
Intraspecific hybridization in animal husbandry is a method of industrial breeding, while individuals of different breeds and lines mate. Remote hybridization in animals - obtaining hybrids between varieties, species and genera (fine-fleeced sheep and argali; cattle and zebu) is difficult and their hybrids are usually infertile. Industrial crossbreeding pursues the goal of obtaining custom animals, i.e. those that can be used by themselves for their work, but they cannot serve for breeding purposes. Example: in Moravia, Pointers were mated with German Pointers, their goal was to obtain dogs that were balanced in temperament and suitable for work in local conditions.
1. Interbreed hybridization
hybridization genetic intraspecific
Interbreeding of dogs, the offspring of which, in contrast to the hybrid, are called crossbred or mestizo. Crossbreeds easily interbreed and produce offspring. Depending on the goal, different crossing methods are used. As a result of crossing, the heterozygosity of the resulting animals increases sharply, which often leads to heterosis, i.e. powerful development of crosses, which sometimes have superiority over the best of the original breeds. The formation of the heredity of crossbreeds is influenced not only by the signs inherent in the breeds, but also by the signs characteristic of individuals, lines and offspring. Producers who give good offspring when purebred are usually good when crossed. In crossbreeds from crossbreeds, heterosis disappears, splitting of traits occurs, the appearance of undesirable qualities and a break in the correlations that have developed in the original breeds are observed. Interbreeding occurs most often due to the fact that the breeder is trying to improve a certain breed of working or hunting dogs, adding endurance, sensitivity, etc. to it. Consider interbreeding on the example of huskies. Interbreeding of Laikas is often noted in those areas where these dogs are used for their intended purpose, where the culture of dog breeding is small. There are frequent cases of mating of huskies of different breeds and in those areas where there is a system of pedigree records. And very often, crossbreeds are issued documents on the origin. There are known cases of mating of Russian-European Laikas with West Siberian Laikas (puppies were black and white in color) and in the pedigrees they were considered Russian-European Laikas. Growing up, such crosses often have good shapes. In the first generation, they are often very good workers, so hunters mate their Laikas with Laikas of other breeds. However, random crossing does not bring anything good (especially if these dogs are also given pedigrees). And, of course, there is nothing in common with those methods of interbreeding, which, depending on specific conditions, can be not only justified, but also necessary in selection and breeding work. With reproductive (factory) crossing, they seek to create a new breed from two or more breeds. When breeding Laikas, reproductive crossing is not used. Although the Russian-European Laika was bred to a certain extent by the method of reproductive crossing. For this purpose, producers of two breeds were used, and their descendants were bred in “themselves”. In itself, reproductive crossing is one of the most complex types crossing. From the point of view of the genotype, it is not difficult to point out the way to work with this crossing, but from a purely animal-breeding point of view, various problems and difficulties arise in crossing. Reproductive crossing can be divided into two types, although this division is purely formal. The first type is a simple crossing, which consists in the fact that no more than two breeds participate in the creation of a new genotype. The second type is just a complex crossing, i.e. more than two breeds are the original ones, and a certain sequence is used when crossing. But for a more accurate reproduction, we need to keep in mind what we want to get as a result and therefore we must outline a genetic plan for working with these breeds.
Absorption crossbreeding is a method of crossbreeding that is used very widely and its essence is that the worst breed is improved using another, better breed for this purpose. Absorption crossing, carried out over a number of generations, can eventually give such a large modification of the phenotype and genotype of a given group of animals that they will practically approach the group being improved. The breed to be improved is called improved, and the one with which improvement is carried out is called improving. The method of absorptive crossbreeding is very often and in a primitive form used by hunters to improve their different types of huskies. The essence of this method lies in the fact that crossbreeds obtained from the mating of local dogs and good imported pedigree sires are again mated with pedigree sires until the crossbreeds, in their external forms and working qualities, approach the qualities of the improving breed. It turns out that the improving breed, as it were, absorbs the improved one. For convenience and general characteristics of the breed of local offspring, albeit conditionally, they began to divide: 1/2 - half-breeds; 3/4 - blood; 7/8 - blood and 15/16 blood. The method of absorption crossing itself requires a certain planning of breeding work, strict rejection of unwanted crosses, very careful selection and selection of producers, both from the side of the improving breed and among crosses.
An introductory crossing is often referred to as a "blood drop" infusion. This crossing is used in cases where the existing breed suits you as a whole and you would like to keep its basic qualities, but it needs to correct some shortcomings, as well as to enhance its valuable properties. This can be achieved by choosing an improving breed, which is close to the improved breed in character, working qualities and body type, but has well-defined features that are poorly developed in the improved breed. In order not to change the type of the breed being improved, it is necessary to confine ourselves to obtaining crossbreeds of the first generation, which are then mated with the producers of the main breed being improved. An introductory crossing is a slight departure from purebred breeding, in which a kind of “fresh blood” of the improving breed is carried out. In selection and breeding work with Karelian-Finnish Laikas, introductory crossing was necessary: the breed as a whole suited hunters, but due to systematic inbreeding, it had some drawbacks. To improve the Karelian-Finnish Laika, there was a very close Finnish Laika both in type and in working qualities. The blood of Finnish huskies was carefully added to the Karelian-Finnish Laika, and the resulting crosses were crossed with the Karelian-Finnish. In other places, absorption crossings were mainly carried out, in which the Korelo-Finnish Laika disappeared and was replaced by the Finnish.
Today, another hybrid has appeared. This is a fashionable fad, and dogs obtained from two completely unsuitable breeds are called designer dogs. The first to cross a poodle with a Labrador. The result was a shaggy dog with wavy hair and a long tail, extremely kind and playful. Another big plus of this breed is that the coat of the Labrapoodle does not cause allergies. Designer breeds are gaining popularity and people can order anything (smooth-haired lapdog or shaggy Doberman). It is often not possible to determine what breed the parents of these dogs were. Let's take a couple more examples of experimental breeders. In America, the newfangled breed of dogs "PUGGL" is gaining strength. The result of crossing two very popular dog breeds: the bulldog and the beagle. The result was a miniature, unpretentious dog with a typical face for bulldogs, expressive eyes characteristic of beagles and huge flapping ears. Puggle wool is hypoallergenic. The idea of breeding dogs of a new species originated in America 7 years ago. As David Barber (one of the breed's breeders and owner of Dog Paradise in Brooklyn) says, it's like crossing a Versace bag with a workout bag. In one bottle you get the best of both breeds. In Japan, in contrast to the puggle, the poodle and the Maltese were crossed, the new breed was called the “panda dog”. The coat of the puppies is dyed to look like a panda with a special paint for wool. The idea to paint the dog in such a way arose due to the fact that the tear ducts near the eyes stood out very much on the white wool, so the Panda Dog owners decided to hide the flaws and give the dog a spectacular look. The paint lasts for several months, and then the dog needs to be repainted. These mestizos are gaining popularity. They are acquired by Hollywood stars, giving them a lot of money. I would call it a “trade-commercial crossing for one day”. These breeds are needed as long as there is a demand for them, and until some breeder breeds a prettier dog and the old ones are forgotten. A lot of people disapprove of the idea of genetically designed dogs. “Modified dogs will never have the same characteristics as purebreds,” says Lisa Peterson of the American Kennel Club. We are forced to seriously warn buyers who impose on their customers the best qualities of both of its prototypes in a unique combination in the new design.”
Interline crossing. Interline crossing can also be attributed to hybridization. But in order to understand this, one must first understand what a pure line or purebred breeding is. Many breeds are reproduced almost exclusively by pure breeding. This method involves mating dogs belonging to the same breed. The method of pure breeding allows you to get offspring similar to their parents in external forms, working qualities, hereditary and breeding values. With purebred breeding, genotypic properties become more stable, which increases the likelihood of obtaining offspring with desirable qualities. The most important thing in pure breeding is the preservation of the valuable properties of the breed for its further improvement. The improvement of the breed can continue for a long time, because. absolute homogeneity of rocks does not exist. A pure line, as a rule, is carried out with the help of related mating (inbreeding). During inbreeding, individuals that are in varying degrees of kinship mate. Supreme form purebred breeding - breeding along lines - is impossible without the use of inbreeding. Inbreeding can have both positive and negative effects. Using inbreeding, we concentrate hereditary inclinations and get dogs that are homozygous for a number of traits - this allows us to quickly consolidate valuable properties in the breed and create a homogeneous population. At the same time, related breeding contributes to the impoverishment of the genotype, a decrease in fertility and productivity, the appearance of deformities, and a decrease in resistance to diseases. But inbreeding works differently on different dogs. ON THE. Iln and I.F. Antipin cite facts when, for a number of generations, closely related breeding of dogs was carried out and no negative phenomena were noted. And in the modern practice of dog breeding there are many undesirable consequences of close inbreeding. Line breeding provides for the creation within the breed of a hereditarily stable group of breeding dogs, descended from outstanding producers and possessing valuable qualities similar to them. The line is part of the breed, so it is similar to it and at the same time different from it. Qualitative originality lies in the type inherent only to this line, which may differ from the type of breed. In dogs, this can be expressed in the features of the exterior (color, head shape, etc.), special working qualities, etc. An outstanding sire from which the line originated is called the ancestor or founder, and the line is often called by his nickname. The creation and maintenance of breeding lines is not only obtaining a group of valuable animals, but, above all, a system of zootechnical work, in which offspring are obtained from outstanding producers who are similar to each other in a number of generations, both in phenotype and in genotype. It is also important to remember that at all stages of working with the line, not so much related matings play a decisive role, but rather selection and selection. Thanks to an outstanding manufacturer, a line is created, but it is still not durable and persists for two or three generations. The preservation and isolation of qualitative differences is greatly influenced by their branching and merging with other valuable lines, as a result of which new lines may arise. Such a merging of lines and their branching can also be attributed to one of the types of hybridization.
Interspecific crossing. Interspecific crossbreeding refers to the crossing of individuals belonging to different animal species. Animals of different species often mate heavily with each other - this is caused by many factors: 1) differences in the structure of the genital organs in different species; 2) the absence of a sexual reflex in a male to a female of another species; 3) the death of spermatozoa in the genital tract of females of another species; 4) the absence of a reaction of spermatozoa to the egg of females of another species, making fertilization impossible; 5) death of the zygote; 6) impaired fetal development; 7) complete or partial infertility of hybrids, etc. When using artificial insemination, the first two factors are excluded, and as for the non-crossing of different species caused by other reasons, only single experiments are known that are not fully verified and have methodological errors. With complete infertility, both sexes of hybrids do not give offspring, with partial infertility, one sex is infertile, in one of the original species, which often leads to the loss of valuable features of hybrids. Hybrid offspring often experience heterosis (increased life force), which is more pronounced than in hybrids. The most ancient in the practice of animal husbandry are hybrids of a horse with a donkey and a mare with a male - a donkey (mule, hinny), a horse with a zebra (zebroid), humped camel with two-humped (nar), yak and zebu with cattle. Hybrids, as a rule, surpass their parents in many indicators: working capacity, endurance, productivity, etc. Dogs are also crossed with wolves (wolf) and jackals (srbaka Sulimov). The German scientist Gilzheimer received a triple hybrid: a wolf - a jackal - a dog. And interestingly, a fox with a dog does not give offspring. N.I. Ilyin in his book “Genetics and Breeding of Dogs” claims that the described “fox-dogs” are the product of an error or delusion, even artificial insemination between a fox and a dog remains without consequences. And on wolves - dogs, you can dwell in more detail, since work in this direction has been going on for a very long time. Obtaining hybrids of dogs and a wolf has its roots in the distant past. The Roman historian Pliny the Elder wrote that the Gauls used to tie their bitches in the woods to mate with wolves. C. Darwin, referring to many researchers, wrote that the North American Indians, in order to improve the breed of their dogs, crossed them with wolves. Professor S.A. Gruner argued that the peoples of North-Eastern Siberia and Kamchatka deliberately injected wolf blood into their huskies. Hybrids were obtained, which were valued for agility, endurance, the ability to endure hunger for a long time and run long distances, which is important for these peoples. The wolf mostly acted as an improver of sled dogs, although there are many examples of improving the hunting qualities of dogs. L.A. Sabaneev, in the notes to the second chapter of his work devoted to the wolf, writes: “In Lithuania, from the admixture of wolf blood, excellent (hounds) dogs are obtained. This circumstance was well known to the ancient canine hunters, and it has been used to this day. So, according to legend, Timashev's greyhounds in the Ufa province are famous for their viciousness, they originated from a hybrid of greyhounds with wolves. Recently, the wolf breed of dogs has been bred by the famous Tver hunter P.I. Belovensky. Such information is very interesting. But there is a problem. On the one hand, crossing a dog with a wolf to get a hybrid with a more valuable property is not difficult for an experienced dog breeder. But on the other hand, such hybridization is not a very common occurrence. Let's try to understand this in more detail. Careful studies of wolf-dog hybrids conducted by German scientists indicate that the behavioral traits of the wolf clearly dominate in first-generation hybrids: they are all shy, cautious and timid. Hybrids of the second generation differed great variety on outward signs. Some of them looked like a wolf and some like a dog. But almost everyone was characterized by fearfulness. Based on the obtained results of crossing a dog with a wolf, German scientists deny the possibility of improving the qualities of dogs, stating: “Crossing a dog with a wolf does not give the desired results. The wolf is a shy, extremely cautious and distrustful animal. And this property, being dominant, when crossed with a dog, is steadfastly transmitted to offspring. But at the same time, Professor N.A. Ilyin wrote that wolf-dog hybrids of the first and second generations can be trained like ordinary dogs. A.T. Voilochnikov came to a similar conclusion as the German scientists. and Voilochnikova S.D., who conducted a hybridological experiment at the Kirov VNIIOZ. And at the Perm Military Institute of the Internal Troops of the Ministry of Internal Affairs of Russia, an experiment was set up to breed wolf-dog hybrids. The experience was successful. Hybrids were trained for the mine-detection service, at the border, etc. In this institute, for the first time in world practice, contrary to all previous experience, hybrids of a wolf and a dog of the first generation were obtained, which do not show pathological fearfulness, including in relation to humans, and this does not depend on their cultivation and upbringing. And this proves that wolves do indeed have both genes that determine shyness towards humans, and genes that determine loyalty towards him. They purchased a two-year-old she-wolf, who at the age of three was mated to a German shepherd dog. She was bred to the next estrus by the same male. The third heat - was not tied. The fourth estrus - was mated by a male from her second litter. Fifth estrus - repeated mating with a male from her second litter, but there was an empty one, which ended in a false pregnancy. It is also important to note that the first two litters of hybrids had 50% wolf blood, and the fourth 75%. After analyzing the results obtained, paying particular attention to behavioral trait- Loyalty, tolerance to the person, came to certain results. The reaction of hybrids of the first litter to strangers is distrust, keeping a distance, but without panic. All hybrids of this litter are characterized by neophobia. Skis, bicycles, strollers, umbrellas, cameras in the hands cause an avoidance reaction, mainly in individuals with black color, and what is most interesting, neophobia was practically not detected in two hybrids with a zone color, they were more collected and quickly adapted to the new environment. But there were problems when changing the trainer. In the second litter, only one puppy had some self-doubt and timidity. The rest of the hybrids were more liberated, did not shade themselves in a new environment, were not afraid of strangers. Puppies of the third litter from three to four weeks of age, in contrast to the previous litters, very actively and curiously ran up to the fence of the enclosure when people appeared, but at the age of 7 weeks only one puppy passed the Campbell test, and the rest of the test result predicted serious problems in socialization. The following conclusions were made: hybrids are emotionally very restrained; have much greater physical strength and endurance than dogs; shots and explosions are no problem for them; training is very quickly understood and assimilated; operant skills are easily developed by clicker training; they have a higher instinct than a dog (search for an offender in caches during a search of an object does not exceed one minute, for dogs from one and a half to four minutes, with a standard of six minutes); characterized by rationalism. Hybrids participated in sporting events through the Perm Regional Service Dog Breeding Club and won prizes.
Recently, three breeds of service dogs have been bred on the basis of a German shepherd crossed with a wolf. Sarlos Wolfdog: It was bred in the Netherlands by Lendert Sarlos. In 1975, the Dutch club recognized the breed, which was registered with the FCI in 1981 under the name of the Sarlos Wolfdog (Sarlos Wolfhond). At present, sarloos are widely used in Holland as guides for the blind, as well as in the rescue service, to search for people in the rubble and to save the drowning. The second carrier of about 25% of the wolf genotype was bred in Czechoslovakia and was named “Volchak”. The third dog was bred in Italy. All these dogs retained the behavioral traits characteristic of the wolf, which are unusual for dog breeders dealing with ordinary German Shepherds. Many dog breeds are not devoid of the presence of wolf genes in their genotype. Sled dogs of the Arctic even in the time of A. Brem resembled local wolves.
In addition to wolves, dogs also crossed with jackals. These hybrids amaze with their strength and sharpness of flair. Wolf-dog hybrids are inferior to the wolf in size and strength, and jackal-dog hybrids, on the contrary, are superior to the jackal in size and strength. Forensics are of particular interest to jackal-dog hybrids. Their sense of smell is so strong that they distinguish the sex of a person by smell, and they could differentiate male and female scent traces with a half-hour difference. Hybrids of jackal-dogs also show qualities that are not characteristic of either a jackal or a dog. For example: jackal-dogs from the first to the third generation were distinguished by their exceptional ability to climb. However, half-breeding hybrids during reproduction in “themselves” with each new generation moved away from the original forms, showing more and more new signs of which neither jackals nor dogs had. Some individuals were larger than their parents, while others were very small. Some, regardless of size, were aggressive and constantly attacked their relatives, showing in fights the techniques of wolves and jackals, which did not allow them to be used either for work or for reproduction, while others, on the contrary, were so loyal to their partners and people that with them nothing was a problem. Thus, it can be concluded from all of the above. It is possible to use a wolf and a jackal with a dog in hybridization, but it is better to use them as improvers of dog breeds. Since this is a very laborious work, it should be done by research centers, institutions designed for such work. After all, the breeding of hybrids is a complex matter that requires appropriate conditions and a long time.
Interspecific hybrids of animals are usually unable to produce offspring, as the process of formation of germ cells is disrupted. But they themselves, in addition to their unusual appearance, sometimes show qualities that are superior to their parent species (larger, more hardy, etc.). This phenomenon is called heterosis.
Buzzle is a hybrid of a ram and a goat. In 2000, a ram and a goat were accidentally crossed in Botswana. The animals were simply kept together. The new animal was named "Toast of Botswana". At the ram and goat different amount chromosomes - 54 and 60. Therefore, their offspring are usually stillborn. But the surviving hybrid was able to inherit the signs of both of its parents at once. Him long wool like a sheep, and goat's feet. The outer hair was coarse and inner part wool is soft. The animal turned out to have a heavy ram's body. At 5 years old, it weighed 93 kilograms. The animal had 57 chromosomes, which turned out to be the average between the number of its parents. The hybrid turned out to be very active, with increased libido, although sterile. That is why at 10 months he was castrated. Cases of obtaining such a hybrid were noted in New Zealand and Russia.
Bison - a hybrid of bison and american bison. The breed was created to combine the characteristics of both animals and to increase beef production. Bison give fertile offspring both when crossing between themselves and with representatives of the original species.
The creation of bison turned out to be a serious problem for the conservation of the population of wild american bison. Most modern bison are already genetically bison, as they appeared as a result of crossing two species.
Beefalo is a hybrid of a cow and an American bison. the breed was bred in order to get the best source of meat. In bifalo, it is bright red, which is important, because. such meat contains less cholesterol than traditional beef. Breeders also claim that bifalo meat has a more delicate and delicate taste and aroma, but so far the general public has not been able to appreciate it - the meat is sold only in a few US stores.
Grolar (polar grizzly) is a hybrid of a grizzly bear and a polar bear. Found in captivity and in the wild. It is distinguished by thick creamy white fur, long claws, a humpbacked back, dark spots around the eyes and nose.
The killer whale is a hybrid of a bottlenose dolphin and a small black killer whale. Quite a rare hybrid, currently only two specimens live in marine park entertainment in Hawaii. The size of the hybrid is average between a killer whale and a dolphin; the difference in the number of teeth is interesting: the dolphin has 88, the killer whale has 44, and the hybrid has 66.
Liger and tiger. A liger is a hybrid of a lion and a tigress, a tiger is a hybrid of a tiger and a lioness. Ligers are very large, they know how and love to swim, they are sociable. Their males are sterile, but the females can bear offspring. Tigerlions are smaller.
2. Hybrids of hybrids
We are talking about crossbreeds between a male tiger and a female liger/tiger lion or a male lion and a female liger/tiger lion. Female ligers and tigers can give birth. Such second-level hybrids are extremely rare and are mostly privately owned.
The lionpard is a hybrid of a lioness and a leopard. The body resembles a leopard, there is also a characteristic color. The spots are not black, but brown. But the head is more like a lion's. The size of the new hybrid exceeds the size of a leopard. Leopard loves to climb trees and swim in the water. The first documented mention of this animal is found in 1910 in India. The most successful experiments on the removal of levopard were carried out in Japan. The lioness Sonoko from the leopard Kaneo in 1959 gave birth to two cubs, and three years later three more. Male hybrids were infertile, the last of them died in 1985. But one of the females was able to give birth to offspring from a hybrid of a lion and a jaguar.
Savannah is a hybrid of a wild serval and a domestic cat. The servakot turned out to be a beautiful and strong animal. The unusual look became popular among breeders in the late 20th century, and in 2001 International Association Koscheck fixed it as a new registered breed. Savannahs are much more outgoing than regular house cats and are often compared to dogs due to their devotion to their owner. They can be trained to walk on a leash and even fetch items thrown by their owner. According to the standards, the servakot should have black or brown spots, silver or black. Usually these animals have high erect ears, a long thin neck and head, short tail. Servakot's eyes are blue in childhood and green during adulthood. These cats weigh from 6 to 14 kilograms. They are not cheap, as for pets - from $ 600 and above.
The Iron Age pig is a hybrid of domesticated Tamvor pigs with wild boars. So it turns out a pig from the Iron Age. This hybrid is much more tame than the wild boar. However, it is not as malleable as ordinary domestic pigs. The resulting animals are raised for their meat, which is used in some specialty sausages and other products.
Fish red parrot. Asian love it aquarium fish constantly creating new species. This species was bred in Taiwan in 1986. How such a mutation was obtained is still a secret. After all, this allows local breeders to continue to maintain a monopoly on these fish. Rumor has it that the midas cichlid was crossed with a red cichlid. Their fry are gray-black, but by 5 months they become bright orange or pink. We learned this fish in the 90s, they bring it here from Singapore and other countries South-East Asia. If a red parrot is placed in an aquarium, then the fish can grow up to 10-15 centimeters there. The color can vary greatly, in addition to orange, yellow is also possible. At some point in their lives, parrots can be crimson, purple, and bright red. However, over time, they all acquire an orange color. Experts advise feeding this fish with special food with carotene, this will help enhance the bright red color of their body. The resulting hybrid also has some pronounced anatomical deformities. For example, the mouth looks like a narrow vertical slit. Because of this, these fish are very difficult to feed, which is why many of them die prematurely. Bester is a hybrid of beluga and sterlet, fish of the sturgeon family. First received in the USSR in 1952. The hybrid combines the rapid growth of the beluga with the early maturation of the sterlet. Length up to 2 meters, weight up to 30 kg. The hybrid is fertile. In aquaculture, hybrids of the first generation grow to a weight of 1 kg or more in 2 years.
Hybrid Pheasant - A hybrid of a golden pheasant and a diamond pheasant. As a result, the new bird received a unique coloring of its plumage.
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Since ancient times, people have been fascinated by the beauty and diversity of the surrounding plants, especially flowers. Their aroma and tenderness in all ages has been the personification of love, purity, manifestation of feelings. Gradually, a person realized that he could not only enjoy the existing views of these beautiful creatures, but also take part in their formation. Thus began the era of plant breeding, leading to the production of new species with more necessary and important features in the geno- and phenotype. The two sciences working together on this issue have managed to achieve fantastic results so far - and botany.
Botany
Botany is the science that studies everything related to plants. That is, they are:
- morphology;
- genetics;
- physiology;
- anatomy
- taxonomy.
This discipline covers all aspects of the life of representatives of the flora, starting with the internal processes of respiration, reproduction and photosynthesis and ending with the external diversity of phenotypic traits.
This is one of the most ancient sciences, which appeared along with the development of man. Interest in the creatures growing around him, so decorating the surrounding space, has always been with a person. In addition, in addition to beauty, it has always been a powerful source of food, medicinal components, building material. Therefore, botany is a science that studies the most ancient, important, diverse and complex organisms on our planet - plants.
plant breeding
With the passage of time and the accumulation of theoretical knowledge about the structure of these creatures from the inside, their way of life and the processes taking place in them, an understanding of how their growth and development can be manipulated has also become available. The science of genetics was gaining momentum, which made it possible to study different objects at the chromosomal level, to cross them with each other, to get bad and good results, to choose profitable and necessary ones. This became possible thanks to the following discoveries.
- in plants.
- Discovery of the processes of mitosis and meiosis.
- Development of crossing methods.
- The phenomena of heterosis, outbreeding and inbreeding.
- Deciphering the genetic code of plants.
- Biomolecular studies of the composition of cells and tissues.
- Discoveries in the field of cytology and histology.
Of course, this is not all the prerequisites that served as the beginning of a powerful movement and the development of plant breeding methods.
Crossing and its characteristics
Another name for the crossing process is hybridization. The method of using this phenomenon is called hybridological. Gregor Mendel was the first to use it for his experiments. Every schoolchild knows his famous experiments on peas.
The essence of the whole process is to cross parental forms with each other in order to obtain offspring that are heterozygous in terms of characteristics, which will be called a hybrid. At the same time, different types of crossing have been developed. They are selected taking into account the individual characteristics of the variety, species or genus. There are two main types of such processes.
- Outbreeding or outbreeding. Implies that the initial parent forms do not belong to the same species, genus or variety. That is, they are not related. Such crossing is one of the most popular and most often leads to heterosis when breeding pure lines.
- Inbreeding or inbreeding- closely related hybridization of individuals belonging to the same species or genus, variety. This method is used to fix a useful trait in a population, including a phenotypic one. With repeated correctly carried out incubation, it is possible to obtain genetically pure plant lines.
These types of crossing also have narrower varieties within themselves. So, one of the forms of outbreeding is crossbreeding - hybridization between varieties.
In addition to types, there are also different types of crossing. They were described and studied in detail by Mendel, Thomas Morgan and other geneticists of the past centuries.
Types of crossing
There are several main types of hybridization of individuals.
- Monohybrid, or simple. It implies the crossing of parental forms to obtain the first offspring, carried out once.
- Dihybrid - parents are taken as the basis, differing in two pairs of signs.
- Returnable - a hybrid from the first generation is crossed with the original parent.
- Polyhybrid, or double - individuals of the first generation are then crossed among themselves, and subsequent ones with other varieties and species.
All of the indicated varieties have a meaning in each specific situation. That is, for some plants, a simple crossing is enough to get the desired result. And for others, complex phased polyhybrid hybridization is required to obtain the desired trait and consolidate it in the entire population.
Hybrids of different generations
As a result of any crossing, this or that offspring is formed. The traits that it took from its parents can manifest themselves to varying degrees.
Thus, the characters of hybrids of the first generation are phenotypically always uniform, which is confirmed by (the first) and his experiments on peas. Therefore, it is often the monohybrid type of hybridization that is used to obtain the same result, which is required only once.
Further, all subsequent individuals already combine properties in themselves, so splitting appears in certain ratios. Recessives appear, intervene. Therefore, the most important for the industrial activity of man, his agriculture, is precisely the first generation of plants obtained.
A typical example: if the goal is to produce only yellow tomatoes as a result of one seasonal period, then a yellow and a red tomato should be crossed, but the red should be obtained earlier from the yellow parent. In this case, the first generation will certainly be uniform - yellow tomato fruits.
Interspecific hybrids: characteristics
Interspecific hybrids are those that are obtained as a result of outbreeding or distant crossing. That is, this is the result of mating individuals belonging to different species in order to obtain a new one with predetermined characteristics and properties.
In this way, many important agricultural and ornamental plants, and many new species of individuals have been bred in animal breeding.
Examples of such organisms
Examples of interspecific hybrids among plants:
- grain fodder wheat;
- triticale - wheat and rye;
- rye-wheatgrass forms;
- wheat-elimus;
- several types of tobacco and others.
If we talk about animals, then also many representatives can be cited as an example:
The main problem with such hybridizations is that the offspring are either sterile or not viable. That is why people have created and developed a lot of ways to eliminate these factors. After all, if the desired result is obtained, then it is very important not only to fix it, but also to introduce the production of such organisms into the system.
What is the reason for the infertility of interspecific hybrids?
The reasons for such problems lie in the processes, namely in anaphase, when the chromosomes diverge towards the poles of the cell. At this moment, each of them is looking for its homologous pair. This is how whole chromosomes are formed from chromatids and the general karyotype of the organism is formed.
But in those individuals in which the fusion occurred from different parental forms, the possibility of meeting such structures is minimal or impossible. That is why a random combination of traits occurs and as a result, individuals become infertile or unviable. That is, genes, in fact, become incompatible.
If we turn to the molecular level and find out what is the reason for the infertility of interspecific hybrids, then the answer will be this: it is the incompatibility of DNA sections from the cell nucleus and mitochondria. As a result, there is no conjugation of chromosomes in the meiotic process.
This leads to disastrous results both in crossing and breeding breeds and new species of animals. Especially often this happens in representatives of the flora. Therefore, you can get a crop of hybrid plants only once, which is extremely inconvenient for the development of agriculture.
After it became clear to scientists what the reason for the infertility of interspecific hybrids was, active work began to find a way to eliminate these causes. This led to the creation of several methods for eliminating the sterility of individuals.
Ways to overcome infertility
The main way that biologists have chosen to solve this problem is as follows. At the stage of meiosis, when the chromosomes diverge towards the poles of the cell, a special substance, colchicine, is introduced into it. It promotes the dissolution of the spindle fibers (cell center). As a result, all chromosomes remain in one cell, and do not fall into different ones. Now free conjugation between homologous pairs is possible, which means that the process of meiosis is quite normal in the future.
Thus, the offspring becomes fertile and easily bears fruit in the future when crossed with different forms. Most often, this method is used in plant breeding, it is called polyploidy. It was first applied by our scientist Karpechenkov. So he got the first fertile hybrid of cabbage and radish.
What is the reason for the infertility of interspecific hybrids, we have already found out. Knowing the nature of the problem, we managed to create two more ways to solve it.
- Plants pollinate with pollen from only one parent. This method allows you to get several generations of hybrid individuals, fertile. However, then the trait still returns, and the individuals become sterile again.
- Pollination of hybrids in the first generation with pollen from parents.
To date, more methods of struggle have not been created, but work in this direction is underway.
Lilies and their hybrids
A symbol of purity and innocence, flowers of sadness and grief for the departed, gentle and delicate representatives of lilies - lilies. These plants have been valued by man for many centuries. During this time, no varieties have been created! Naturally, interspecific crossings touched them too.
The result was the development of nine groups of hybrid varieties that simply amaze with the beauty of phenotypic traits! Among them, a special place is occupied by the two most unusual and sought-after representatives:
- oriental hybrids;
- lilies are OT hybrids.
Consider the features of both groups and give them a description.
Oriental hybrids
This is the largest hybrid in terms of flower formation. Their biology is practically no different from that of other representatives. The dimensions of the growing calyx can reach 31 cm in diameter, and the color can be different. The Nippon variety is very beautiful, having large white flowers with a pink border. Their petals are corrugated.
The height of these plants ranges up to 1.2 m. This allows them to be planted at a distance of 20-25 cm from each other and form beautiful flowering ridges. All representatives of this group exude a very strong aroma.
Orienpits
This is the OT-hybrids lilies, the abbreviation of which is formed from the full name: oriental-tubular forms. They are also called for the very high size of the plants and large flowers. On one stem up to 2.5 meters high, over 25 large (up to 30 cm) flowers can form, which are very fragrant and brightly colored.
This allows this group of hybrids to be very popular with gardeners, although not everyone can cope with their breeding. Very careful care and proper planting are required so that such forms can take root and produce offspring.
Sunflower and its hybrid forms
Sunflower hybrids differ from each other in terms of seed ripening. So, allocate:
- early maturing (up to 90 days);
- early ripening (up to 100 days);
- mid-season (up to 110 days).
Hybrid seeds also give unequal. Oil content and yield are excellent and depend on the ripening period. The longer the plant is in the ground, the higher the quality of the crop. You can name some of the most common hybrids of this plant in the world, most in demand in agriculture.
- Tunka.
- Bosphorus.
- Rocky.
- PR64A15.
- Jason.
- Forward.
Among their main advantages:
- drought tolerance;
- diseases and pests;
- productivity;
- high quality seeds;
- good fruiting.
Hybrid (from lat. hybrid) - the creation of a new individual by crossing living organisms of various breeds, species, varieties. The hybridization process is applied mainly to living things (animals, plants).
The article will focus on the creation of such organisms in the animal world. These are the most difficult experiments. Also, the reader will be able to see animal hybrids, photos of which are placed in sections.
Story
The first attempts to create hybrids were carried out as early as the 17th century by the German botanist Camerarius. And in 1717, the English gardener Thomas Freidchild presented the scientific community with a successful result of hybridization - the new kind carnations.
In the animal kingdom, things were much more complicated. In the world of wildlife, it is extremely rare to find animal hybrids. Therefore, the crossing of representatives of different species occurred artificially - in laboratory conditions or in reserves.
The very first hybrid with a thousand-year history is, of course, a mule - a mixture of a donkey and a horse.
Since the middle of the 19th century, with the advent of nature reserves and zoos (in the form in which we are accustomed to seeing them in modern times), they began to cross bears - brown and white, as well as a zebra with a horse.
Since the middle of the 20th century, scientists around the world have been conducting experiments on crossing different animal species. All of them have different goals: someone breeds hybrids to improve productivity, someone - for exotics, and someone - to obtain effective drugs.
Animal hybrids: what are they?
There are more than 80 interspecific hybrids all over the world, but let's focus on the brightest and most famous representatives.
Peasley
Peasley (aknuk) - a cross between a polar bear and a grizzly bear. The first mention of an unusual animal dates back to 1864. Then in the northwestern part of North America, near Lake Rendezvous, a bear with an unusual dull white color and a golden brown muzzle was shot.
10 years later in german zoo(Galle) the first offspring was obtained from polar and brown bears. Babies were born white, but over time, the color changed to bluish-brown or golden-brown. Peasley showed good results in terms of reproduction: hybrid animals successfully produced offspring. Interbreeding took place both between Aknuk and with representatives of a pure line.
Often, interspecific hybrids of animals are not reproductive, but pizzles are an exception, since both bears can be attributed to the same species by biological characteristics, but, based on a number of morphological features, the bears were identified by scientists as separate species.
Even before 2006, there was an opinion that animal hybrids did not occur in the natural environment. This myth was dispelled on April 16, 2006 by American hunter Jim Martell, who shot a Peaseley on Banky Island (Canadian Arctic), which became indisputable evidence of the appearance of hybrids in the wild.
Liger and tiger
The first is a hybrid of a tigress and a lion, and the second is the offspring of a lioness and a tiger. These animal hybrids are born exclusively in artificial conditions, the reason for this is banal - different habitats (Africa and Eurasia) do not allow them to meet, this is possible only in menageries.
Outwardly, ligers look like a cave lion, which became extinct during the Pleistocene period. To date, this hybrid is considered the largest among the cats. This phenomenon is explained by growth genes: in tigers they are not as active as in lions. For the same reason, the tigrolev is smaller than the tiger.
In the amusement park "Jungle Island" (Miami, USA) contains a male liger named Hercules weighing 418 kg. For comparison: the average weight of the Amur tiger varies from 260 to 340 kg, and the African lion - from 170 to 240 kg. So, Hercules absorbs up to 45 kg of food in one approach, and develops a speed of 80 km / h in 10 seconds.
The remarkable thing about ligers is that these cats love to splash in the water. Another feature: ligers are one of the few hybrids that are able to reproduce offspring. So, in the Novosibirsk Zoo on August 16, 2012, the lion Samson and the ligress Zita became parents, giving birth to the liligric Kiara.
There are just over 20 ligers in the world today.
Bester
Bester is a hybrid of two representatives of the sturgeon family - a female beluga and a male sterlet. Bester owes its appearance to the Russian scientist-biologist - Professor N. I. Nikolyukin. Since 1948, he has come to grips with the problem of sturgeon hybridization. In 1952, the wife of Nikolai Ivanovich, who, together with her husband, worked on the creation of fish hybrids, tried to artificially obtain offspring of sterlet and beluga. The Nekolyukins did not expect that this unscheduled experiment would mark the beginning of a new direction in fish farming.
During the experiments, the professor crossed different types of sturgeons, but the turn did not reach the beluga and sterlet. Perhaps he considered such an experiment initially a failure, since these sturgeons are different in size and weight (beluga - up to a ton, and sterlet - no more than 15 kg), live and spawn in different places, and their hybrids cannot produce offspring. But everything happened exactly the opposite.
Bester took fast growth from beluga, and fast puberty from sterlet, which is an important factor for industrial fish. Also, the hybrid turned out incredibly tender meat and delicious caviar.
Now in Russia besters are bred on an industrial scale.
Kama (camel)
It is a hybrid between a male Bactrian and a female llama. The first kama saw the light in 1998 at the Animal Reproduction Center in Dubai. The individual was created artificially, the main purpose of such crossing was to get an animal with the endurance of a camel and the quality of llama wool. The experiment was a success. Kama turned out to weigh up to 60 kg, with wool at least 6 cm long, with the ability to carry loads up to 30 kg. The disadvantage of the camel is the inability to reproduce. Of course, in nature, such an option would be impossible, since llamas live in South America, and Bactrians - in Asia and Africa, and in size the former are significantly inferior to the latter. Despite these data, it turned out that the camel and the llama have the same number of chromosomes.
To date, six individuals of kam have been received in the UAE.
Kosatkodelfin (wolfin, kitofin)
Kosatkodelfin - a hybrid of killer whale (small black) and bottlenose dolphins. The first wolfin appeared in a water park in Tokyo, but died at the age of six months. The second orca dolphin hybrid appeared in Hawaii at the SeaLifePark Marine Park in 1986. The female wolffin, named Kekaimalu, began breeding at the age of five, which is quite early for killer whales and dolphins. The first experience of motherhood was somewhat unsuccessful: the mother refused to feed the baby, so she was artificially fed, which made it possible to grow an absolutely tame individual, but her life was short and ended at the age of 9 years. Kekaimalu experienced the happiness of motherhood three times, but the last one turned out to be the most successful: in 2004, the female Kavili Kai was born from a male bottlenose dolphin. The baby turned out to be very playful, and a month after birth she reached the size of her father.
An interesting fact was discovered by scientists: the wolffin has 66 teeth, the bottlenose dolphin has 88, and the killer whale has 44.
Now in the world there are two individuals of the orca dolphin, which are kept in Hawaii. Sometimes information appears that wolffins have been seen in the wild, but scientists have not yet been able to confirm this data.
Other hybrids
Let's see what are the most common animal hybrids. The examples are quite interesting. These are the following hybrids:
- domestic horse and zebra - zebroid;
- donkey and zebra - zebrul;
- bison and bison - bison;
- sable and marten - kidas;
- cichlids - red parrot;
- female African lion and leopard - levopard;
- leopard and lioness - leopon;
- capercaillie and black grouse - mezhnyak;
- dromedary and bactrian - nar;
- lioness and tiger - tigon;
- hare hare and white hare - cuff;
- cows and yaks - hainak (dzo);
- ferret and mink - honorik;
- leopard and jaguar - jagopard.
But these were obtained in the course of many experiments
- horse and donkey - mule;
- donkeys and stallion - hinny;
- ram and goat;
- diamond and golden pheasants - a hybrid pheasant;
- domestic and American bison cows - bifalo;
- a hybrid obtained by crossing musky drakes with Beijing white, Rouen, Orgpington, White Allier ducks - Mullard;
- domestic pigs with wild boar - a pig from the Iron Age.
You can talk about animal hybrids for a very long time, given their number and diversity. But are there other options, such as animal-plant hybrids?
To date, there is only one known hybrid - the sea snail (Elysia chlorotica), which lives on the coast of North America from the Atlantic Ocean. These animals feed on solar energy: eating plants, they photosynthesize. The snail has been dubbed the gelatin green plant. This hybrid receives chloroplasts, which are then stored in intestinal cells. An interesting fact: a sea snail with a lifespan of no more than one year can eat only the first two weeks from the moment of birth, after which food consumption becomes a non-priority.
Plant-animal hybrids have become commonplace, but how would the public react to a human-animal hybrid? And do they exist?
There are many rumors about the existence of such hybrids, but, unfortunately, there are very few facts. However, studying the mythology of different peoples, scientists point to the presence of beastmen in almost all epics. Scientists from Australia and the USA have studied more than 5,000 rock paintings and texts. Most often there are descriptions of people whose bodies (as a rule, the lower part) consist of the body of a horse, goat, ram, dog. The names of such beastmen are well known to us from mythology. These are centaurs, minotaurs, satyrs and others.
Scientists explained the existence of such "people" by the fact that in ancient times bestiality was common, especially in the army, because herds of sheep and goats were always kept nearby. Animals were for the military not only potential food, but also objects of satisfaction of sexual needs. Many scientists of the Middle Ages mention the birth of children from animals in women and vice versa. These facts remain a big question, since from a biological point of view this is impossible due to a different set of chromosomes.
Recently, more and more new, ambiguous facts have been revealed to the public. One of these facts is the experiment on the fertilization of a woman with the sperm of a chimpanzee in fascist Germany and the USSR. According to some reports, the Soviet Union, after a series of attempts, received positive result. Further fate experiment has not yet been disclosed.
A hybrid of a human and an animal is nonsense for modern society, but information about such experiments continues to appear in the media. Is this true or fiction? We will judge in 10-20 years. Time will tell how far science will go, but for now we will eat hybrid fruits and vegetables, enjoy the beauty of hybrid plants and animals and hope that humanity will not return to the Stone Age.
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