Plant breeding
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What is plant breeding?
Plant breeding applies genetics to create plants beneficial to humans. This involves choosing plants with desirable traits and controlling their mating, then selecting specific offspring. Repeating this over generations changes the plant's genetic makeup, exceeding natural limits. Plant breeders aim for an ideal plant with combined traits like disease and insect resistance, climate tolerance, suitable size, and high yield.
Early selective breeding dates back to the beginnings of agriculture. Around the mid-1800s, Gregor Mendel's work with pea plants outlined heredity principles, creating a framework for scientific plant breeding. Today, plant breeding is vital for promoting global food security.
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Why do people breed plants?
People breed plants to create plants with a combination of desirable traits, such as disease resistance, tolerance to different environmental conditions, and better quality. Plant breeders also consider traits like size, shape, maturity time, and aesthetic appeal.
Plant breeding can increase crop yield, improve nutritional value, and adapt plants for mechanized agriculture. It also helps in developing varieties that can withstand extreme weather, thus promoting global food security. The modification of crops can extend their production area, as seen in the development of early-maturing grain sorghum varieties that allowed the crop to be grown further north.
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How are new plant varieties created?
Plant breeders apply genetic principles to develop plants that better serve humans. They select plants with desirable traits, control their mating, and then select individuals from the resulting progeny. This process, repeated over generations, can significantly alter a plant's hereditary makeup beyond natural limits.
Methods include selecting superior plants from variable populations and evaluating their offspring. Hybridization, or crossing genetically diverse lines, creates new gene combinations. Breeders aim for ideal plants with multiple desirable traits like disease resistance, stress tolerance, and improved yield and quality. Genetic engineering techniques are also used to modify plants. Ultimately, the goal is to develop varieties better adapted to their environment, easier to grow, and more nutritious.
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What is crossbreeding in plants?
In plant breeding, crossbreeding, or hybridization, involves breeding plants with different traits to produce offspring with desired characteristics. This method aims to combine favorable genes from two or more varieties, resulting in superior progeny.
Cross-pollination, the transfer of pollen from one plant to another, offers evolutionary advantages by increasing genetic variety, which is essential for species survival in changing environments. The process involves selecting superior plants and self-pollinating them for generations to create purebred lines. Then, these lines are crossbred to restore vigor, resulting in hybrid varieties with improved traits.
The plant breeder's task involves managing the numerous genotypes that arise following hybridization to create new pure-line varieties. Superior types are selected over successive generations, with pedigree records maintained. Field trials are conducted to assess performance, quality, and potential weaknesses before a new variety is released for commercial production.
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How does plant breeding help with disease resistance?
Plant breeding uses genetic principles to create plants that are more useful to humans. Disease-resistant plant varieties offer a safe, effective, and inexpensive method for controlling many crop diseases. Plant breeders develop disease-resistant plants through artificial selection, introduction from an outside source, induced variation, or a combination of these methods. Methods for breeding plants for disease resistance are like those for breeding other characteristics, except that two organisms are involved: the host plant and the pathogen. Thus, it is necessary to know about the nature of inheritance of the resistant characters in the host plant and the physiological races or strains of the pathogen.
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What are some modern techniques used in plant breeding?
Modern plant breeding techniques apply genetic principles to create plants more beneficial to humans. These methods include selecting plants with desirable traits and controlling their mating to select specific progeny. Over generations, these processes change the plant population's genetic makeup beyond natural limits.
Some modern techniques are:
* Recombinant DNA techniques Transgenic modification is routinely used.
* Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) Gene editing is mainly done through CRISPR, which is taken from a bacterial mechanism that can cut out specific sections in DNA. CRISPR is used in creating genetically modified organism crops. The functional precision of CRISPR allows researchers to remove and insert DNA in desired locations within a genome, making it possible to correct genetic defects in animals and to modify DNA sequences in embryonic stem cells.
* Budding and grafting Plant breeders use budding and grafting techniques to maintain desirable gene combinations initially obtained from crossbreeding.
* Doubling chromosomes The chemical compound colchicine, which causes chromosomes to double, has resulted in many new varieties of fruits, vegetables, and flowers.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Plant breeding, application of genetic principles to produce plants that are more useful to humans. This is accomplished by selecting plants found to be economically or aesthetically desirable, first by controlling the mating of selected individuals, and then by selecting certain individuals among the progeny. Such processes, repeated over many generations, can change the hereditary makeup and value of a plant population far beyond the natural limits of previously existing populations. This article emphasizes the application of genetic principles to the improvement of plants; the biological factors underlying plant breeding are dealt with in the article heredity. For a discussion on transgenic crops, see genetically modified organism.
History
Plant breeding is an ancient activity, dating to the very beginnings of agriculture. Probably soon after the earliest domestications of cereal grains, humans began to recognize degrees of excellence among the plants in their fields and saved seed from the best for planting new crops. Such tentative selective methods were the forerunners of early plant-breeding procedures.
The results of early plant-breeding procedures were conspicuous. Most present-day varieties are so modified from their wild progenitors that they are unable to survive in nature. Indeed, in some cases, the cultivated forms are so strikingly different from existing wild relatives that it is difficult even to identify their ancestors. These remarkable transformations were accomplished by early plant breeders in a very short time from an evolutionary point of view, and the rate of change was probably greater than for any other evolutionary event.
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In the mid-1800s Gregor Mendel outlined the principles of heredity using pea plants and thus provided the necessary framework for scientific plant breeding. As the laws of genetic inheritance were further delineated in the early 20th century, a beginning was made toward applying them to the improvement of plants. One of the major facts that emerged during the short history of scientific breeding is that an enormous wealth of genetic variability exists in the plants of the world and that only a start has been made in tapping its potential.
Goals
The plant breeder usually has in mind an ideal plant that combines a maximum number of desirable characteristics. These characteristics may include resistance to diseases and insects; tolerance to heat, soil salinity, or frost; appropriate size, shape, and time to maturity; and many other general and specific traits that contribute to improved adaptation to the environment, ease in growing and handling, greater yield, and better quality. The breeder of horticultural plants must also consider aesthetic appeal. Thus the breeder can rarely focus attention on any one characteristic but must take into account the manifold traits that make the plant more useful in fulfilling the purpose for which it is grown. Plant breeding is an important tool in promoting global food security, and many staple crops have been bred to better withstand extreme weather conditions associated with global warming, such as drought or heat waves. Although traditional, heirloom plants generally are not as disease-resistant or productive as many modern hybrids, many have been selected for their superior flavours, and their colours and shapes are aesthetically pleasing. In addition, many heirlooms are also exquisitely adapted to the region in which they were developed and hold valuable genetic resources for that can be useful in the breeding of hardier varieties.
Increase of yield
One of the aims of virtually every breeding project is to increase yield. This can often be brought about by selecting obvious morphological variants. One example is the selection of dwarf, early maturing varieties of rice. These dwarf varieties are sturdy and give a greater yield of grain. Furthermore, their early maturity frees the land quickly, often allowing an additional planting of rice or other crop the same year.
Another way of increasing yield is to develop varieties resistant to diseases and insects. In many cases the development of resistant varieties has been the only practical method of pest control. Perhaps the most important feature of resistant varieties is the stabilizing effect they have on production and hence on steady food supplies. Varieties tolerant to drought, heat, or cold provide the same benefit.
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Modifications of range and constitution
Another common goal of plant breeding is to extend the area of production of a crop species. A good example is the modification of grain sorghum since its introduction to the United States in the 1750s. Of tropical origin, grain sorghum was largely confined to the southern Plains area and the Southwest, but earlier-maturing varieties were developed, and grain sorghum is now an important crop as far north as North Dakota.
Development of crop varieties suitable for mechanized agriculture has become a major goal of plant breeding in recent years. Uniformity of plant characters is very important in mechanized agriculture because field operations are much easier when the individuals of a variety are similar in time of germination, growth rate, size of fruit, and so on. Uniformity in maturity is, of course, essential when crops such as tomatoes and peas are harvested mechanically.
The nutritional quality of plants can be greatly improved by breeding. For example, it is possible to breed varieties of corn (maize) much higher in lysine than previously existing varieties. Breeding high-lysine maize varieties for those areas of the world where maize is the major source of this nutritionally essential amino acid has become a major goal in plant breeding. This “biofortification” of food crops, a term which also includes genetic modification, has been shown to improve nutrition and is especially useful in developing areas where nutritional deficiencies are common and medical infrastructure may be lacking.
In breeding ornamental plants, attention is paid to such factors as longer blooming periods, improved keeping qualities of flowers, general thriftiness, and other features that contribute to usefulness and aesthetic appeal. Novelty itself is often a virtue in ornamentals, and the spectacular, even the bizarre, is often sought.