Selective Breeding(redirected from Backyard breeding)
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selective breeding[si′lek·tiv ′brēd·iŋ]
(in Russian, selektsiid), (1) The science concerned with methods of creating animal breeds and plant varieties and hybrids.
(2) A branch of agriculture engaged in introducing new animal breeds and plant varieties and hybrids. Selective breeding develops methods of altering the genetic composition of plants and animals in a direction in accord with human needs. The process is a form of evolution of the plant and animal worlds that obeys the same laws as the evolution of species in nature, but natural selection is partly replaced by artificial selection.
Selective breeding has played a major role in supplying the earth’s population with food. Thanks to animal domestication and primitive selective breeding, Neolithic man had almost all the same food crops and many of the livestock species we have today. Plant and animal productivity grew considerably as commercial and scientific selective breeding developed. The development of plant varieties and animal breeds became a means of agricultural production and an important factor in plant growing and livestock raising on an industrial basis. For example, short-stemmed nonlodging varieties of grain crops suitable for combine harvesting were produced, as were vegetable varieties suitable for cultivation in hothouses, grapes and tomatoes suitable for machine harvesting, and cattle adapted to maintenance in large livestock complexes.
Selective breeding is a continuous process. Its methods are constantly being improved to meet increasing demands for new varieties and breeds of greater productivity, higher quality, and greater resistance to disease and pests. It is also promoted by the introduction of crops and livestock species into new regions and by changes in the technology of growing crops. The wheat varieties Liutestsens 62, Tsezium 111, and Ukrainka, which yielded 25–30 quintals of grain per hectare (ha), were widely distributed in the USSR in the 1930’s and 1940’s. These wheat varieties have been replaced by Bezostaia 1, Mironovskaia 808, Avrora, Kavkaz, Mironovskaia lubileinaia, and other varieties having a productivity of 50–70 quintals per ha. In the 19th century the cultivation of vitreous red spring wheat over much of the Canadian prairies and on the northern Great Plains in the United States was made possible by the introduction of the early ripening Red Fife variety, which was replaced in the early 20th century by the Marquis variety. Marquis wheat ripened several days sooner than Red Fife, thus permitting the wheat belt to be enlarged. The introduction of new breeds of sheep adapted to Siberian conditions made possible the relocation of fine-wooled-sheep raising to new regions. The great demand for colored mink encouraged the breeding of animals with pale yellow, light blue, pearly, and sapphire fur.
Selective breeding is closely related to taxonomy, anatomy, morphology, physiology, plant and animal ecology, biochemistry, immunology, horticulture, zootechny, plant pathology, entomology, and other sciences. A knowledge of the biology of pollination and fertilization, embryology, histology, and molecular biology is especially important in selective breeding.
N. I. Vavilov defined selective breeding as a highly complex science that borrows and transforms laws dealing with plants and animals from other sciences. Selective breeding uses these methods and laws discriminatingly in accordance with the end purpose of developing a variety, develops its own methods, and determines the phenomena that lead to the creation of a variety or breed.
The theoretical foundation of selective breeding is genetics, whose main principles have become the basis of breeding practice. Darwin’s theory of evolution, Mendel’s laws, and research on pure lines and mutations enabled breeders to work out methods of controlling the heredity of plants and animals. The individual selection of plants and animals is based on pure lines, homozygosity, heterozygosity, and nonidentity of phenotype and genotype. The patterns of independent inheritance and free combination of characters in offspring served as the theoretical basis of hybridization and crossing, which together with selection are the principal methods of selective breeding. The development of genetics led to the creation of heterotic corn, sorghum, cucumber, tomato, beet, wheat, cattle, and poultry hybrids; to the use of plants with cytoplasmic male sterility; and to the inducement of artificial mutations and polyploid forms. Hybrid analysis plays an important role in selective breeding. Genetics, in turn, draws information from selective breeding, thus enabling it to elaborate its own theories.
History. Selective breeding arose with crop cultivation and animal domestication. After man began to grow crops and raise animals, he began to select and reproduce the most productive ones, thereby contributing to their unintentional improvement. Thus, primitive selective breeding, appearing at the dawn of human culture, has a history thousands of years old. Ancient breeders created excellent varieties of fruits and grapes, several wheat varieties, and various breeds of domestic animals. They were familiar with some modern methods of selective breeding. For example, date palms were artificially pollinated in Egypt and Mesopotamia several centuries before the Common Era.
With the development of crop cultivation and livestock raising, artificial selection of the best forms became widespread. Russian peasants created wheat varieties (Krymka, Beloturka, Poltavka, Garnovka), sunflower varieties (Zelenka, Fuksinka), tall local strains of fiber flax (Smolenskii, Pskovskii), a clover variety (Permskii), and apple varieties (Antonovka, Grushovka) that were given old or local names and were well adapted to local growing conditions. The best Soviet and American cotton varieties originated from cotton cultivated by the Maya. In Peru large-kernel corn of the Cuzco group, created many centuries ago, is cultivated. Popular selective breeding over the centuries produced the Karakul and Romanov sheep breeds, the Arabian and Akhaltekinskaia horse breeds, Gray Ukrainian cattle, and the Yaroslavl’ and Kholmogory dairy cattle breeds. Local varieties and breeds were used for further selection.
The development of capitalism greatly influenced selective breeding and led to such breeding on an industrial scale. In Great Britain the first selection nurseries were established in the late 18th and early 19th centuries; pedigree animal breeding was organized at this time also. R. Bakewell developed the Leicestershire sheep, an outstanding meat-and-wool breed, and the brothers C. Colling and R. Coiling bred Shorthorn cattle. Great Britain supplied many countries with pedigree animals.
Interest in creating new plant varieties increased in the second half of the 19th century. In Germany, F. Achard began the selective breeding of sugar beets to obtain a high sugar content and yielding capacity. Wheat varieties produced by the British breeders P. Shiref and F. Gallet and by the German scientist W. Rimpau became widespread. Commercial seed companies and large enterprises for selection and seed growing were established in Europe and America. The Vilmorins Company, which was founded in 1774 near Paris, supplied all of France with seeds and exported seeds to many countries. In Russia the Poltava Experimental Field (1884) and experimental sugar-beet selection stations were organized. It was at the Poltava Experimental Field that the varietal composition of Verkhniachskaia (1883), Nemerchanskaia (1886), and Uladovo-Liulinetskaia (1886) wheats was studied. I. V. Michurin had great success in the selection of fruit crops. In Sweden the Svalöv Breeding Station (1886, today an institute) played a major role in the development of selective breeding in Western Europe; its oat varieties (Golden Rain, Victory, Ligovo II) and other crop varieties became known throughout the world. In the United States experimental selection stations and laboratories were organized in every state. Private seed-growing companies also engaged in selection work. Fruit and ornamental varieties were bred by L. Burbank.
In the late 19th century extensive plant collections were gathered in the United States, France, Great Britain, Sweden, and other countries, and new varieties were introduced into cultivation. Plant collections served as a new source for producing new varieties. Discoveries in botany, zoology, and microscopy had a great influence on selective breeding, and the process became increasingly mechanized with the invention of special instruments and machines.
Despite its considerable progress, industrial breeding lacked the scientific prerequisites that later enabled it to become a theoretically substantiated science. Eighteenth- and 19th-century breeders based their work only on experimentation and intuition, although they used many modern methods. Decisive factors for the emergence of selective breeding as a science included Darwin’s theory of evolution and the development of general genetics and later of plant genetics, animal genetics, and radiation genetics. The first theoretical substantiations of selective-breeding methods were provided by the Danish geneticist W. Johannsen (1903) and the Swedish breeder and geneticist N. Nilsson-Ehle (1908, 1911, 1912). Studies on chemical and radiation mutagenesis (the Soviet geneticists M. N. Meisel’, 1928; V. V. Sakharov, 1933; I. A. Rapoport, 1943; the British geneticist C. Auerbach, 1944) and evolutionary genetics (the Soviet scientist S. S. Chetverikov, 1926; the American geneticist S. Wright and the British geneticist J. Haldane, 1920’s and 1930’s) have had great significance for the development of selective breeding. After the theoretical foundation was laid and new methods were used, selective breeding evolved into a science for controlling the heredity of organisms.
In Russia scientific selective breeding was first practiced in 1903. It was in that year that D. L. Rudzinskii organized selection stations as part of the Moscow Agricultural Institute (today the K. A. Timiriazev Moscow Agricultural Academy); the country’s first cereal and flax varieties were created at these stations. In the same year courses were given for the first time on selection and seed production at the Moscow Agricultural Institute; soon afterward the subjects were taught at other higher educational institutions. Between 1909 and 1914 the Kharkov, Saratov, Bezenchuk, and Odessa experimental stations were established. In 1911 the first congress of breeders and seed growers was held in Kharkov to review the work done by experimental organizations. The Bureau of Applied Botany, Genetics, and Selection, which was organized in 1894 by R. E. Regel’, played a major role in the development of scientific selection. The bureau successfully studied the varietal composition of cultivated plants.
Selective breeding made great advances after the October Revolution of 1917. The decree On Seed Growing, signed by V. I. Lenin in 1921, laid the foundation for a single state system of selective breeding and seed production in the USSR. During the 1920’s and 1930’s a network of new scientific selection organizations was created, state grain testing was instituted, crop varieties were regionalized, and considerable research was carried out on genetics and selective breeding. Vavilov’s law of homologous series in hereditary variability and his theory of centers of origin of cultivated plants began to be used extensively in selection work, as were ecological and geographic principles and research on planting material and plant immunity. M. F. Ivanov, P. N. Kuleshov, and A. S. Serebrovskii made major contributions in establishing the genetic basis of animal selection. The elaboration of the theory of distant hybridization is associated with the names of G. D. Karpechenko and I. V. Michurin. The All-Union Institute of Applied Botany and New Crops, which was organized in 1924 and later transformed into the All-Union Institute of Plant Growing, became under Vavilov’s direction a world center for the collection and study of plants. The many plants collected by the institute provided starting material (gene pool) for many plant varieties.
Objectives and methods. Selective breeding for yielding capacity, the main criterion of a variety, remains the principal objective. Breeding for quality is becoming increasingly important. For example, some plants are bred for high content of desirable substances (starch in potatoes; protein in wheat, feed barley, and corn; oil in sunflower seeds, soybeans, and rape; sugar in sugar beets) or low content of undesirable compounds (alkaloids in lupine, protein in brewing barley, nitrogenous substances in sugar beets). Plants may be bred for processing suitability (good milling and baking qualities of wheat, suitability of fruits and vegetables for canning, suitability of groats for soft boiling) and for keeping quality (fruits, vegetables, potatoes, fodder root crops). Selective breeding is also carried out to alter the content of essential amino acids (lysine, tryptophan) in cereal proteins, the chemical composition of oil, and the length of fiber. Plants are bred for resistance to disease, pests, cold, frost, and drought, as well as for hardiness and adaptability to irrigation, large quantities of fertilizers, and machine harvesting. The combination of several objectives ensures the creation of high-yielding varieties that have various specific properties and characters and that are adapted to particular soil, climatic, and farming conditions.
Animals are bred for productivity and product quality (butterfat yield, protein content, and amino acid composition of milk; length and thickness of wool; size of eggs), fecundity (especially in sheep and swine raising), color of pelt, and adaptability to local conditions.
The principal methods employed in selective breeding are selection, hybridization (by means of heterosis and cytoplasmatic male sterility), polyploidy, and mutagenesis. Mass and individual selection, the essence of selective breeding, yields various properties and characters. Hybridization makes it possible to produce starting material artificially, combine the properties and traits of the parental forms in one organism, and correct specific shortcomings of a variety or breed. Through hybridization, especially distant hybridization (for example, geographically distant forms, different species and even genera), one can produce new forms unlike the original. The selection of pairs for crossing frequently determines the success of the breeding effort. Natural and hybrid populations, self-pollinated strains, artificial mutants, and polyploid forms are used as starting material. In the USSR the collection of the All-Union Institute of Plant Protection and foreign varieties are used as starting material. The matching of pairs based on the genetics of the characters to be bred is effective. If the number of genes responsible for the inheritance of the characters is known, the frequency of appearance of the required combinations of parental characters in the hybrid plants can be predicted. The matching of pairs by ecotypes (ecological-geographic method) differing in genotype, as well as in economically useful and biological properties and characters, has won universal recognition. Crossing distant ecotypes produces the best results. Multiple and back hybridization based on repeated crossings is used to produce in the hybrid offspring certain valuable properties that cannot be obtained by single crossings. Hybridization followed by selection has produced many modern varieties of grain, oil, fodder, vegetable, and fruit crops.
Breeders use heterosis to obtain hybrids that are highly productive in the first generation, especially hybrids of corn, sorghum, cucumber, tomato, and sugar beet. The principal way of using heterosis is to cross specially chosen pairs of varieties or self-pollinated (inbred) strains. In beets, sorghum, and other crops hybrid seeds and hybrid plants may be obtained only if cytoplasmic male sterility is present in the maternal plants. Most corn hybrids are also bred on this sterile basis.
Polyploidy can be used to obtain plants with an increased number of chromosomes (triploids, tetraploids) that differ from diploid plants. Polyploids are marked by their intense color, thick leaves and stems, vigorous development, and high content of protein, sugar, and starch. Heterotic sugar beet triploids obtained by crossing tetraploids with diploids are widely used in commercial farming. Since triploids are mostly sterile, only the first generation is used. High-yielding rye, red clover, and other crop varieties have been obtained by using polyploidy.
Artificial mutagenesis is one of the most promising methods of selective breeding. Mutations, that is, hereditary changes, can be induced by exposing seeds and plants to various types of radiation and chemical agents. Radiation mutagens produce a wider spectrum of mutations. Forms with useful changes in several properties are obtained from mutants produced by treatment with chemical agents. There are various ways of using mutants; a simple selection of useful mutations is possible. Mutants may be crossed with one another or with varieties. Valuable pea, oat, barley, perennial grass, bean, lupine, and other mutants have been obtained and introduced into production.
Advances in the USSR. Great advances in selective breeding have been made during the years of Soviet power, resulting in sharply higher yields. The Bezostaia 1 winter wheat variety (intensive type), which was bred by P. P. Luk’ianenko and coworkers at the Krasnodar Institute of Agriculture, was regionalized in 1959. The variety was developed by the hybridization of geographically distant forms followed by individual selection; its yielding capacity is 40–50 quintals per ha. International strain testing conducted in 1969–70 confirmed that Bezostaia 1 was the best winter wheat variety for all the wheat-growing regions. The new and promising Avrora and Kavkaz varieties bred by Luk’ianenko are even more productive, yielding 55–70 quintals per ha. Among the popular varieties bred by V. N. Remeslo, Mironovskaia 808, Mironovskaia Iubileinaia, and Il’ichevka yield more than 100 quintals per ha on crop-testing plots. The drought-resistant Saratovskaia 29, Saratovskaia 210, Saratovskaia 38, and other spring-wheat varieties with first-class grain quality bred by the Institute of Agriculture of the Southeast (A. P. Shekhurdin and V. N. Mamontova) occupy about 60 percent of the area planted with wheat (26 million ha in 1974). N. V. Tsitsin, whose work on distant hybridization of cereal grains is well known, was the first in the world to obtain wheat-couch grass hybrids, wheat-wild rye hybrids, and perennial and feed wheats. In wheat breeding special efforts are being made to create high-yielding hybrids, short-stemmed winter and spring wheat varieties with useful characters for irrigated agriculture, and rye-wheat amphidiploids high in protein (triticale).
Corn has also been successfully bred. The high-yielding hybrids Bukovinskii 3TV, VIR 42MV, VI R156TV, and Krasnodarskii 303TV have been developed for relatively widespread cultivation. Many of the hybrids yield 120–150 quintals of grain per ha under irrigated conditions. M. I. Khadzhinov obtained hybrids rich in lysine (Krasnodarskii 303VL, Kubanskii 4VL), which when fed to animals produced large weight gains and a 20–30 percent saving in the amount of feed consumed.
Sunflower varieties created by V. S. Pustovoit and his colleagues contain 51–56 percent oil in the seeds and are resistant to the sunflower moth and to a combination of broomrape and downy mildew. The best of these sunflower varieties are Peredovik Uluchshennyi, Smena Uluchshennaia, and VNIIMK 6540 Uluchshennyi. In 1974 varieties high in oil content occupied more than 95 percent of the area under sunflower cultivation in the USSR.
Monospermous sugar beet varieties were obtained for the first time by O. K. Kolomiets, S. P. Ustimenko, and others. High-yielding monospermous hybrids rich in sugar and polyhybrids (triploids obtained by means of polyploidy) have been introduced into production. They include the Ialtushkovskii hybrid, Belotserkovskii polyhybrids 1 and 2, and Pervomaiskii polyhybrid; these varieties occupy more than 60 percent of the area planted with sugar beets. A. L. Mazlumov and his associates developed Ramonskaia 06, Ramonskaia 100, and other varieties for cultivation over fairly extensive areas. Cotton has been successfully bred for wilt resistance. In 1974 the new wilt-resistant Tashkent 1, Tashkent 3, and 133 (S. Mirakhmedov, S.S. Sadykov) occupied about 60 percent of the area planted with cotton. Good results have also been obtained in breeding potatoes, vegetables, feed crops, and fruit crops. The best Soviet varieties occupy extensive areas abroad.
Considerable success has been achieved in the selective breeding of animals. Very valuable breeds of cattle (Kostroma, Kazakh White-faced) and sheep (Askaniaia, Krasnoiarsk, Kazakh Arkhar-Merino) have been created. The Askaniia breed of sheep yields more wool annually (30.6 kg) than any other sheep breed. Selective breeding produced karakul sheep yielding pelts of various colors. Strains of poultry have been produced to obtain rapid-maturing hybrids for meat and egg production.
In the USSR all aspects of selective breeding are interrelated and combined into a single centralized state system. More than 400 scientific organizations deal with plant breeding and more than 500 with animal breeding. There are now 27 selection centers for the development of grain and fodder crops. The V. I. Lenin All-Union Academy of Agricultural Sciences and the Ministry of Agriculture of the USSR direct selection work. The N. I. Vavilov All-Union Society of Geneticists and Breeders was organized in 1966. The journal Selektsiia i semenovodstvo (Breeding and Seed Growing) has been published since 1929 (entitled Semenovodstvo [Seed Growing] until 1935). The USSR is a member of the European Association for Research on Plant Breeding and conducts research under the sponsorship of the Council for Mutual Economic Assistance.
Advances abroad. Breeders in several foreign countries have achieved great success by using the same methods as those in the USSR. In the United States work in selective breeding is concentrated at state universities, experiment stations (in every state), agricultural colleges, and commercial seed-growing enterprises. Varieties and hybrids from many countries are used as starting material. Considerable success has been achieved in breeding short-stemmed vitreous winter wheat varieties, for example, Gaines, Nugaines, and Caprock. The last variety is high yielding under irrigation conditions and has good milling and baking qualities; it also is immune to orange leaf rust and powdery mildew and is resistant to lodging. The best spring wheat varieties are Red River 68, World Seeds 1502, and World Seeds 1877 (introduced into the USSR in 1975). American breeders are striving to create hybrid wheat and perennial feed wheat that is very bushy, salt tolerant, disease resistant, and rich in protein.
In rice breeding attention is devoted to the development of tall-stemmed varieties that mature early or in midseason and are resistant to low water temperature; also being developed are double-yielding varieties. The most common rice varieties are Nato, Nova, and Colusa. Progress has also been made in the selective breeding of corn. High-yielding hybrids whose kernels are rich in protein, lysine, and oil, as well as popcorn varieties with good taste and technological qualities, have been obtained. Corn is being bred for resistance to lodging, height of attachment of the cobs, resistance to cold and drought, and early ripening. Also being developed are new varieties of feed crops (alfalfa, clover, sweet clover), cotton, soybeans, peanuts, sunflower, and other crops. A number of wilt-resistant, early ripening cotton varieties adapted to machine harvesting have been created, including Dixie, King, Rex, and Del Cerro.
Mexican wheat varieties (Sonora 63, Lerma Rojo, Inia 66, Pi-tic 62), many of which have been bred by N. E. Borlaug and others at the Mexican International Center for the Improvement of Wheat and Corn, have become well known throughout the world, greatly influencing the development of wheat breeding in India, Japan, Turkey, the United States, Canada, and other countries. Mexican varieties are used in the USSR as starting material for the selective breeding of short-stemmed wheat.
In Canada much effort has been devoted to breeding grains, especially short-stemmed wheat varieties resistant to rust (the experiment station in Swift Current, University of Saskatchewan), varieties having large high-quality grains rich in protein and carotene, varieties with good technological qualities (University of Saskatchewan), and varieties resistant to frost (experiment stations in Lethbridge and Ottawa). Varieties from Mexico, the United States, the Soviet Union (Ul’ianovka, Alabasskaia, Bezostaia 1), India, and other countries are used in hybridization. High-yielding varieties of soft wheat (Neepawa and Manitou, which occupied 70 percent of the area planted with wheat in 1974), durum spring wheat (Hercules and Wakooma), and winter wheat (Sundance) have also been created in Canada. In addition, there are valuable feed wheat varieties (Glen Lea is the best) and short-stemmed rye-wheat amphiploids with a high grain content in the spike. The Manitoba Agricultural Station is developing short-stemmed oat varieties with combined resistance to rust, powdery mildew, smut, and other diseases and a high content of lysine, protein, and oil; it is also creating short-stemmed barley varieties that are nonlodging, immune to rust, and suitable for brewing. Good results have been obtained with breeding rhizomatous forms of alfalfa, soybeans, sunflower, and other crops.
In Sweden the selective breeding of plants is done at the Svalöv and Weibullsholm institutes and affiliated institutions. Breeders of barley and oat varieties are concerned mainly with selecting for resistance to lodging, shattering, and germination of grain of standing plants; immunity to powdery mildew, rust, and other diseases; and high protein and lysine content in the grain. The barley varieties that occupied the largest area in 1974 were Singrid and Serla; among the new varieties introduced in 1970–71, the most popular are Wing, Akka, Gunilla, and Christina. The best oat varieties are Selma (grown in many other European countries) and Risto. Pompe and Snabbe (introduced into the USSR in 1974) are the main spring wheats, and Starke II is the principal winter variety. Only insignificant areas are planted with spring wheat in Sweden.
Hybrid potato varieties rich in starch have been obtained in the Federal Republic of Germany, the German Democratic Republic, the Netherlands, and Poland. Sunflower varieties rich in oil (based on varieties from the USSR) have been produced in Rumania, and short-stemmed high-yielding rye varieties have been created in Hungary, the German Democratic Republic, Czechoslovakia, and Poland. Valuable tomato, pepper, and other vegetable varieties have been developed in Bulgaria, as have cucumber hybrids for cultivation in sheltered soil in the Netherlands and durum spring wheat varieties resistant to heat and shattering in Algeria.
Selective breeding has successfully obtained animal breeds having good meat and milk qualities, high egg-laying capacity, and early maturation.
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M. M. IAKUBTSINER, V. F. DOROFEEV, and R. A. UDACHIN