Single-cross hybrids with biotech traits
Polish translation: szczepy hybrydowe zawierające w swoim składzie dwie linie wsobne z cechami biotechnologicznymi
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| 17:44 Mar 23, 2019 |
| English to Polish translations [PRO] Science - Agriculture / general | |||||||
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|  Selected response from: Frank Szmulowicz, Ph. D. United States Local time: 19:25 | ||||||
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| single-cross hybrids with biotech traits szczepy hybrydowe zawierające w swoim składzie dwie linie wsobne z cechami biotechnologicznymi Explanation: cccccccc Odmiany kukurydzy w zależności od sposobu produkcji nasiennej zawierają w swoim składzie dwie (SC – single cross), trzy (TC – three – way cross) lub cztery (DC – double cross) linie wsobne https://www.agrosklad.com.pl/wp-content/uploads/2019/01/kata... ccccccccccccccccccccccc In biology, a trait or character is a feature of an organism. The term phenotype is sometimes used as a synonym for trait in common use, but strictly speaking, does not indicate the trait, but the state of that trait (e.g., the trait eye color has the phenotypes blue, brown and hazel). https://www.sciencedaily.com/terms/trait_(biology).htm ccc Genetically modified crops ("GM crops", or "biotech crops") are plants used in agriculture, the DNA of which has been modified with genetic engineering techniques. In most cases, the main aim is to introduce a new trait that does not occur naturally in the species. Biotechnology firms can contribute to future food security by improving the nutrition and viability of urban agriculture. https://en.wikipedia.org/wiki/Biotechnology |
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| single-cross hybrids with biotech traits mieszańce pojedyńcze (dwulinione) z cechami biotechnologicznymi Explanation: ABY ZROZUMIEĆ O CO CHODZI POLECAM PRZECZYTAĆ PO KOLEI CAŁOŚĆ MOJEGO POSTU: Corn Breeding: Lessons From the Past What is an open-pollinated variety? The name, open-pollinated variety, refers to how the farmers replenished their seed stock. After a new variety was produced by crossing two varieties, a farmer propagated this new variety by saving the seed from the most desirable ears from the most desirable plants each fall. These ears were open-pollinated ears. That is, there was no effort to control the source of the pollen. The pollen that fell on the silks of these ears was dispersed from tassels of nearby plants by wind and insects. The result of this open-pollination was that every plant grown from saved seed was genetically unique. However, all the plants shared certain characteristics that were desirable to the farmer. Grain productivity was certainly one of these characteristics, but not the only one. For example, James Reid, who developed the Reid open-pollinated variety with his father in central Illinois, was an artist. He selected for a corn with a small shank that could be easily hand-harvested without spraining his artist’s wrist. All the open-pollinated varieties grown in the United States in the 19th and early 20th centuries were developed by farmers. There were no professional corn breeders. The farmers were the corn breeders. http://passel.unl.edu/pages/informationmodule.php?idinformat... Corn Grain Yields, 1870 to 1930 From 1870 until about 1930 there was no increase in the U.S. national average corn grain yield (Figure 7). The average yield in the decade of the 1920s was 26.4 bushels per acre (1.8 tons/hectare), which actually was a bushel per acre less than occurred 50 years earlier. What were the reasons for this lack of response? Grain productivity is difficult to change when selection is based on the performance of individual plants and when grain yield is judged visually from the apparent size of ears (grain and cob). When selected ears are open-pollinated ears (i.e. the source of the pollen is not controlled), the effectiveness of selection is reduced because pollen from less desirable (non-selected) plants has pollinated some of the kernels on those selected ears. Selections often were based on characteristics that had nothing to do with actual grain productivity. This apparent contradiction to good farming practices reached its peak of popularity in the corn shows http://passel.unl.edu/pages/informationmodule.php?idinformat... Corn Shows, A Social Phenomenon Corn shows were largely a social phenomenon that became popular in the U.S. Corn Beltbeginning about 1900. In these shows, which were held at county and state fairs in the fall, a variety would be judged based on the appearance of a 10-ear sample. Uniform appearance of both ears and kernels reigned supreme. Thus, selection for uniformity became of paramount importance to many farmers from 1900 to 1920. Some evidence suggests that this selection for uniformity actually caused grain yield potential to decline in open-pollinated varieties. But the prestige of the corn shows was so great, that few of the judges—many of whom were trained at reputable agricultural colleges—ever thought of testing the best of the show corns against similar open-pollinated varieties that were more variable. http://passel.unl.edu/pages/informationmodule.php?idinformat... Inbreeding, Hybrid Vigor, and Hybrid Corn At about the same time the corn shows were peaking in popularity, in the northeast United States two researchers were experimenting with controlled pollinations in corn. Their findings would soon cause a remarkable change in the corn culture of North America. Both Edward East at the Connecticut Experiment Station and George Shull at the Carnegie Experiment Station on Long Island had begun to self-pollinate corn. Under self-pollination, the silks of an ear are pollinated by pollen from the same plant. Typically, little self-pollination occurs in a field of corn. Most silks of a given plant are pollinated by pollen from surrounding plants. This is known as cross-pollination (Figure 8). When a plant from an open-pollinated variety is self-pollinated, all the progeny resemble that plant, although they all differ from each other and from the parent plant to some extent. If one of the progeny plants is self-pollinated, the new progeny again differ from each other and from the parent plant, but the degree of the difference is not as great as occurred after the first self-pollination. If this process is repeated about seven times, then a plant known as an inbred is produced. An inbred is a pure-breeding strain of corn. This means that if an inbred is self-pollinated, all of the progeny will be genetically identical to each other and to the inbred parent. This process of repeated self-pollinations is known as inbreeding. Inbreeding corn results in loss of vigor (Figure 9). In figure 9, the plant at the far left is non-inbred, the plant second from left was produced by one generation of self-pollination, and the two plants on the right were produced by two generations of self-pollination. Inbred plants developed from open-pollinated varieties of corn are not as vigorous or high yielding as the non-inbred plants of the open-pollinated varieties. But what East and Shull observed was that when the self-pollinated plants were cross-pollinated to produce hybrid progeny, these plants sometimes were even more vigorous than the plants from which the inbreds had been developed. This phenomenon is called hybrid vigor (Figures 10a and 10b). A hybrid developed by crossing two inbreds is known as a single-cross hybrid. As is true for an inbred, all plants of a single-cross hybrid are genetically identical to each other. The productivity of a hybrid depends on the relationship between the two inbreds. A hybrid produced by crossing two inbreds developed from different but equally productive open-pollinated varieties usually will produce a more vigorous hybrid than one produced by crossing two inbreds from the same open-pollinated variety. When a single-cross hybrid is allowed to open-pollinate (as happens in a farmer’s field), approximately half the hybrid vigor is lost. This is the basis of the hybrid corn seed industry. The crop produced from open-pollinated seed harvested from a single-cross hybrid will not be as productive as the original single cross. http://passel.unl.edu/pages/informationmodule.php?idinformat... Corn Grain Yields, 1930 to Today The national average corn grain yield in the United States began to increase steadily in the 1940s (Figure 11). In the most recent decade, the average yield was 125 bushels per acre, nearly five times greater than 70 years before. Several studies conducted by universities have indicated that much of this improved yield was the result of improved genetics; that is, it occurred because farmers were planting improved varieties of corn developed through plant breeding. Greater use of fertilizer, more and better herbicides, improved soil tillage, and other altered production practices also contributed to the increased yields The beginning of the yield increase coincides with the beginning of the transition by farmers from planting open-pollinated varieties to planting hybrids. However, not all of the yield increase that occurred during the past 70 years can be explained by hybrid vigor. The yield advantage of a single-cross hybrid produced by crossing two inbreds developed from two different open-pollinated varieties over the average of the two open-pollinated varieties varies greatly depending upon the open-pollinated varieties that are chosen. It may be as great as 100%, but in many instances will be less. But improvement in average yields from 1930 to 2002 was 400%. In addition to hybrid vigor, genetic improvements were made. Today’s single-cross hybrids yield more than the single-cross hybrids of 70 years ago. Also, public corn breeders have developed many varieties (often called populations or synthetics) that are superior to the open-pollinated varieties that were popular before the introduction of hybrids. Why were corn breeders in the mid- and late-20th century able to make such substantial genetic improvements for grain yield, whereas no increase in yields was realized from 1870 to 1930? The development of single-cross hybrids was partly the answer. But two other factors contributed. New testing methods: By the 1920s, many people were beginning to question the validity of the corn shows. One of the outspoken leaders of this anti-corn show group was Henry Wallace, an eventual founder of the Pioneer Hi-Bred Seed Company. Not only did some seed companies and state universities begin conducting yield tests to compare various strains of open-pollinated varieties, but these tests began to be designed using new statistical methods that produced more meaningful comparisons between different entries. This new reliance on yield testing helped to usher in the quick acceptance by farmers of the new higher yielding hybrids when they became available. New breeding methods: For centuries, farmers had made selections based on the performance of individual plants. The seed for the following year’s crop was taken from the most desirable ears from the most desirable open-pollinated plants. This type of selection is known as mass selection. The new professional breeders were using various methods of what is known as family selection. Mass selection and the new selection methods are topics of other lessons in this series. http://passel.unl.edu/pages/informationmodule.php?idinformat... Corn Breeding: Lessons From the Past - Summary and Definitions of Key Words Although corn is grown across the world, it originated in the Americas. Types of corn are called races. Nearly all modern corn grown in the United States belongs to the Corn Belt Dent race, which largely was developed from two other races, the Northern Flints and the Southern Dents. Early American farmers developed and grew open-pollinated varieties, but from 1870 until 1930 the annual average corn grain yield in the United States did not increase. In the 1930s, open-pollinated varieties were gradually replaced by hybrids that were produced by crossing inbreds, and corn yields started to increase. Today, the average corn yield in the United States is approximately five times greater than it was 70 years ago. This increase is partly attributable to new breeding and testing methods that have resulted in genetically superior hybrids. Key Words Zea mays L. – the scientific name of corn. Race – a class of corn in which all plants of that class share certain characteristics, such as ear shape and number of kernel rows. Open-pollinated variety – a variety of corn that is named for the manner in which seed of the variety is propagated across generations. Self-pollination – the type of pollination that occurs when pollen from a single plant falls on the silks of that same plant. Cross-pollination – the type of pollination that occurs when pollen from one plant falls on the silks of a different plant. Inbreeding – a system of mating in which mates are more likely to be related than would occur if mating was random. Self-pollination is an extreme type of inbreeding. Inbred – a pure-breeding strain of corn. Single-cross hybrid – the type of hybrid that is produced when two different inbreds are cross-pollinated. Hybrid vigor – the phenomenon of a hybrid plant having greater vigor than its parents. http://passel.unl.edu/pages/informationmodule.php?idinformat... Corn Breeding: Types of Cultivars Inbreds In the lesson, Corn Breeding: Lessons from the Past of this series [POWYŻEJ] , an inbred (sometimes called an inbred line or simply a line) was described as a pure-breeding strain of corn. When pollen from an inbred plant is placed on the silks either of the same plant (this is a self-pollination) or of another plant of the same inbred (this is cross-pollination) and the resulting seed is grown, all the progeny will be genetically identical to the parental inbred plant(s). The reason for this is that at every locus an inbred is homozygous (i.e., A1A1 or A2A2, etc.). An A1A1 parent (or two A1A1 parents) can generate only A1A1 progeny. (See pictures below) https://passel.unl.edu/communities/index.php?idinformationmo... Single-cross Hybrids A hybrid plant results from a cross of two genetically different plants. The two parents of a single-cross hybrid, which is also known as a F1 hybrid, are inbreds. Each seed produced from crossing two inbreds has an array (collection) of alleles from each parent. Those two arrays will be different if the inbreds are genetically different, but each seed contains the same female array and the same male array. Thus, all plants of the same single-cross hybrid are genetically identical. At every locus where the two inbred parents possess different alleles, the single-cross hybrid is heterozygous. Plants of a single-cross hybrid are more vigorous than the parental inbred plants. In Figures 2a and 2b, the single-cross hybrid plant and ear are shown with the plants and ears of the parental inbreds. Clearly, the hybrid plant is taller and the hybrid ear is larger. The increase in vigor of a hybrid over its two parents is known as hybrid vigor. The genetic basis of hybrid vigor is not completely understood. However, experience has shown that a hybrid produced by crossing two inbreds that are closely related usually will exhibit less hybrid vigor than a hybrid produced by crossing inbreds that are more distantly related. The progeny produced from self-pollination of a F1 single-cross hybrid are known as F2 plants. On average, F2 plants will have vigor that is approximately half-way between the single-cross parental plants and the average of the two inbred grandparents; that is, half of the hybrid vigor is lost. This is illustrated in Figure 3. The F2 ears on the bottom row vary in size, but on average are larger than the ears from their inbred grandparents and smaller than the ear from their single-cross parent. That is why farmers have an incentive to purchase new single-cross hybrid seed each year. When single-cross hybrid seed is commercially produced, one inbred is the male parent and the other the female parent. Either the female parent must be male-sterile (pollen is not produced or is not functional) or the tassel on each female plant must be removed (this is called detasseling) prior to any pollen production (Figure 4). In either case, all the seed produced on the female parent will be single-cross hybrid seed. Developing an inbred from a single-cross hybrid requires approximately seven generations of repeated self-pollinations (Figure 1). Each year in the United States, commercial seed companies produce hundreds of new inbreds and test in field trials many thousands of new single-cross hybrids obtained by crossing these inbreds. Compared to existing commercial hybrids, the vast majority of these new hybrids will be poorer or no better in performance. Only the hybrids that have superior performance in these trials are produced in mass quantities and sold as commercial hybrids to farmers. Considerable time and inputs are required to develop, select, and produce single-cross hybrids. Achieving a high level of cost efficiency of these processes typically requires large-scale operations. https://passel.unl.edu/communities/index.php?idinformationmo... Double-cross Hybrids The most prevalent type of hybrid that was grown in the United States in the 1930’s and 1940’s is known as a double-cross hybrid. As the name implies, producing a double-cross hybrid requires two stages of crossing involving two pairs of inbreds (see diagram below). In Step 1, two pairs of inbreds, A and B and Y and Z, are crossed to produce single-cross hybrids, AB and YZ. In Step 2, the two single-cross hybrids produced in Step 1 are crossed to produce the double-cross. Typically, A and B are closely related and Y and Z are also closely related, but neither A nor B is closely related to Y or Z. Unlike a single-cross hybrid, plants of a double-cross hybrid are not genetically uniform. Compared to single-cross hybrid production, production of double-cross requires an extra step. During the early history of the hybrid seed industry in the United States, this extra step was necessary because the inbreds available at that time produced so little grain that making commercial quantities of seed of single-cross hybrids was difficult. Even though the inbreds of each pair of a double-cross hybrid were related, the resulting single-cross hybrids exhibited sufficient vigor to allow those single crosses to be used successfully as parents in mass production of commercial seed. In most environments, the best single-cross hybrid will have superior performance to the best double-cross hybrid. As breeders gradually improved the performance of inbreds through selection, it became possible to commercially produce the more desirable single-cross hybrids. Double-cross hybrids may become important in the organic corn market. In production of organic hybrid seed corn, herbicides cannot be used. Therefore, seed producers desire parents that have good vigor and can compare successfully against weeds. The single-cross parents of double-cross hybrids have this desired vigor. https://passel.unl.edu/communities/index.php?idinformationmo... ODMIANA MIESZAŃCOWA - CO TO OZNACZA? Od początku historii rolnictwa czyli od około 8-10 tysięcy lat rolnicy starali wysiewać się nasiona, które wyglądały lepiej od innych, były dorodniejsze, pochodziły od roślin dających większy plon. Taka pierwotna selekcja roślin polegająca na doborze osobników do reprodukcji była prowadzona intuicyjnie, bez wiedzy dotyczącej procesów za to odpowiedzialnych. Rolnicy w taki sposób, z każdym kolejnym rokiem wpływali na pulę genową roślin nawet o tym nie wiedząc. Od momentu ustanowienia przez Mendla w XIX wieku prawa dziedziczenia genów, rozpoczęła się era hodowli roślin i zwierząt, a liczba nowych odmian zaczęła rosnąć w tempie geometrycznym. Uprawiane rośliny podlegały kontroli przez hodowców i były selekcjonowane pod względem pożądanych cech. Starano wychwytywać się pojawiające spontanicznie mutacje, a następnie specjalnie je wywoływać by z tysięcy roślin wybierać jedną, która będzie posiadała określoną cechę. Wyprodukowanie odmian mieszańcowych było jednym z najważniejszych wydarzeń w historii rolnictwa i hodowli roślin. Hybrydyzacja roślin rozpoczęła się w roku 1920 roku od kukurydzy i objęła do naszych czasów większość warzyw, kwiatów i roślin rolniczych. Mieszańcami, hybrydami nazywamy pierwsze pokolenie roślin (także zwierząt) uzyskanych ze skrzyżowania ze sobą dwóch linii rodzicielskich. Każda z linii w pierwszym etapie jest samozapylana i nastawiona na uzyskanie jednej lub więcej cech. Ten etap prac hodowlanych może trwać nawet 7 – 8 lat. Hodowla każdej linii rodzicielskiej prowadzona jest osobno dla uzyskania określonej cechy. Pokolenie potomne powstałe ze skrzyżowania pokolenia rodzicielskiego oznacza się symbolem F1. Litera F pochodzi od łacińskiej nazwy filia/filius co oznacza córka/syn natomiast cyfra 1 to kolejność pokolenia w tym przypadku pierwszego. Jeśli wysieje się nasiona uzyskane z pokolenia F1 będzie to wtedy pokolenie F2. Symbol F1 zwyczajowo przyjęło się używać do oznaczenia odmian hybrydowych (mieszańcowych). Odmianom mieszańcowym towarzyszy zjawisko wybujałości. W porównaniu do linii rodzicielskich hybrydy często wykazują szybszy wzrost i większy wigor. Plonują do 25 % więcej w stosunku do populacyjnych.Są bardziej jednorodne pod względem genetycznym niż linie populacyjne i dlatego łatwiej przewidywać ich jakość oraz kształt. Pozwala to np. na bezproblemowy zbiór kombajnem wielu gatunków warzyw. Mieszańce hoduje się by lepiej radziły sobie w złych warunkach środowiskowych, były bardziej odporne na suszę, choroby, spadki temperatur. Uprawa mieszańców wiąże się często z osiągnięciem wyższych plonów, lepszą zdolność kiełkowania. Odmiany hybrydowe wytwarzają silniejszy system korzeniowy i większą masę roślin. Dzięki hodowli wsobnej linii rodzicielskich można wyeliminować cechy niepożądane, a dobre cechy są ujawniane w potomstwie F1. Dla firm nasiennych istnieje jeszcze jeden ważny powód dla którego promują mocno taki rodzaj odmian. Nasiona odmian hybrydowych nie można reprodukować we własnym zakresie i trzeba corocznie kupować je od hodowców co daje im gwarancję zysków. Dodatkowo tylko hodowca ma wiedzę dotyczącą użytych linii do hodowli i sposobu przeprowadzenia krzyżowania. Jednym z największych minusów hybryd oprócz ceny jest konieczność corocznego kupowania materiału siewnego i brak możliwości rozmnożenia go we własnym gospodarstwie. Wysianie nasion pochodzących z pokolenia F1 powoduje uzyskanie zwykle roślin niżej plonujących, mniej zdrowych i bardzo zróżnicowanych pod względem wyglądu. Nie wiadomą jest także jakie cechy rośliny się uzyska, a dodatkowo traci się zalety pokolenia F1. https://www.cenyrolnicze.pl/wiadomosci/produkcja-roslinna/zb... REJESTR ODMIAN KUKURYDZY Wśród zarejestrowanych odmian kukurydzy główne typy hodowlane stanowią mieszańce pojedyncze, czyli dwuliniowe (SC - single cross), składające się z dwóch linii (A x B), oraz mieszańce trójliniowe (TG - three-way cross). Nieliczne mieszańce są podwójne lub czteroliniowe (DC - double-cross). Te mieszańce są produktem krzyżowania dwóch mieszańców pojedynczych (AB) x (CD). W rejestrze odmian kukurydzy jest obecnie 66 mieszańców pojedynczych (55%), 52 mieszańce trójliniowe (43,3%) i 2 mieszańce podwójne. Zaletą mieszańców pojedynczych jest większe wyrównanie morfologiczne i niekiedy wyższe plonowanie, głównie w produkcji na ziarno. Jednak plony nasion tych mieszańców są niższe, a produkcja nasienna trudniejsza, dlatego również ceny nasion są na ogół wyższe niż mieszańców trójliniowych. https://www.ihar.edu.pl/odmiany_kukurydzy.php |
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