Centers of crop origin theory theory of centers of origin of crops Presented by the Soviet botanists and agronomists Н.И. Vavilov. He cultivated plant species on the planet according to the unbalanced distribution of the species abundant, there is a lot of variation in several areas designated as centers of crop origin. Doctrine of the origin of the problem of the formation of early crops for people to attention. But the modern scientific method to explore the origins of crops, began in the Swiss botanist a. De worthy and more. He kinship plant taxonomy and plant geography natural viewpoint crop research, historical and geographical distribution flora, applied archaeological research unearthed the remains of plants and plant cave drawing images, and applications paleontology, history and Verify the location of the origin of crop knowledge of linguistics, first proposed the initial human domestication of plants in the region may be China, southwest Asia and Egypt to tropical Africa, 3, and published the famous "origin of cultivated plants," a book in 1882. Limited to conditions at that time, although the book is not sufficient data and the lack of basic cytogenetics, but there are still major problems of crop origin reference value. Vavilov was under German influence began to engage more worthy of study of the origin of the crop. From 1920 onwards, he has organized a large-scale plant collecting expedition team has visited more than 60 countries, the ecological environment in different regions for nearly 200 visits, collected more than 30 million copies of their crops Relatives relatives specimens and seeds. In the system subsequent collation and analysis of the study, in addition to his application Linnaean nomenclature to classify, but also choose some important crops, by morphology, cytology, genetics, immunology and determination of ability to adapt to the environment, Identification of some of the crop of new subspecies and new variants. On this basis, he was observed by the geographic distribution of these distinguishing species and varieties from the map, which found that the variation of species diversity in the distribution of imbalance, the formation of centers of crop origin concept. The main content of Vavilov believes there are two main centers of origin of crop characteristics: high genetic diversity and dominant gene frequencies, it can be called the gene mutation center or center of diversity. The origin of the most original native origin center. When the crop thus spread to the edge of a range of locations will result in the crop itself and the natural self-isolation and diverse region formed by the new recessive gene, that secondary centers of origin or secondary gene center. In addition, he also found in certain ecological environment, annual herbaceous crops there is a similarity between the parallel phenomenon of genetic variation in traits such as gramineous and leguminous crops in the Mediterranean region showed no exception, lush plants, spike Big tablets, sub-pale, high-yielding disease; while China is the development of short-term crops, plant dwarf, small grain, fast post-grouting, mostly non-awn or awn hook (refer to wheat). He called this phenomenon "the law of homologous series of genetic variability." Vavilov domesticated according to sources, the crop is divided into two categories, one is the purpose of human domestication of plants, such as wheat, barley, corn, cotton, etc., called native crops; the other is associated with native crops weed, when it is propagated to unsuitable for crops and native environment suitable for their growth and have a definite value when it was separated from the human body and become cultivated such crops called secondary crops. Such as oats and rye in the Central and Western Asia are mixed in the raw wheat, barley weeds, while further north due to the cold strong local cultivation of wheat and barley, it was separated out into secondary crops. 1926 Vavilov made at least view Southwest Asia (in Asia), the Mediterranean region, Southeast Asia and tropical America plateau four world centers of crop origin. Later, with the expansion of the scope of the inspection area for further analysis and study materials, and in 1935 proposed the following eight centers of crop origin (Figure 1): ① China - East Asia; ② India - Tropical Asia, including Malaya supplement ④ western Asia;; ⑤ Mediterranean coast and adjacent areas; ③ Central Asia; area ⑥ Ethiopia; ⑦ southern Mexico and Central America; ⑧ South America, including Peru, Ecuador, Bolivia and Chile Liqiluoai Island complementary areas. He believes this eight centers in ancient times due to the mountains, the desert or the sea barrier, which is independent of the development of agriculture, the use of tools, draft animals, cultivation methods vary, each center has a considerable number of valuable crops and diverse of variation, crop breeders seek treasure trove of new genes. With the progress of the development of the study of crop origin, Vavilov's argument has been further revised. If later found that some crops the center of origin is not a native gene is dominant concentrated areas, some variation in crop centers of origin and centers are not the same, and so on. jr Harlan believes crop origin and comprehensive spatial and temporal variability to two factors to be demonstrated, according to the crop diffusion area of distance and size, can be divided into five types: ① native. After a domesticated plant area, never diffuses out of the region, such as the African Guinea curved arm millet (brachiaria deflexa), Mexican American Indian millet (panicum sonorum) and so on. ② half native. Domesticated plants cultivated only in the neighborhood proliferation, such as the African rice (oryza glaberrima) may be the origin of the Niger River basin flooding, and the proliferation of cultivated area just west of Senegal and Guinea coast, east of Lake Chad in this range, namely elsewhere No cultivation. ③ a single center. The origin of domesticated quickly after being cultivated in a large number of similar other suitable areas, does not produce secondary centers. Such as rubber, coffee, cocoa, etc. fall into this type. ④ have secondary centers. Crop from a clear center of native origin spread widely cultivated, forming secondary center of origin of variation in one or several locations. Some important crops such as wheat, barley, corn, sesame, peas, beans, etc. belong to this type. ⑤ no center. Some crops do not see a clear native place of origin, such as sorghum, beans, rape, bananas, etc. in a fairly large range seems to be able to domestication and cultivation. Therefore, the passage of time is not the only factor in the center of the formation of diverse variability, complexity cultivation environment are more likely to cause a variety of types of variation form. Mountains, especially the low-latitude mountain plants of various types of variation reason why. After the mutation produced mainly through the human conscious or unconscious choice, to form different characteristics in different regions of crop types. In addition, Harlan considered a special type of recessive genes for certain crops appeared in a number of narrow ecological regions, forming gene Center, also has a role in promoting the evolution of crops, such as wheat gene Turkey's three small centers. Soviet Π.Π. Zhukovsky propose different crop species small geographic center of more than 100 genes as many as he believes such a small variation in the type of crop breeding center has an important value in use. He will also regionally eight Vavilov centers of origin determined to be included in the expansion, added another four centers of origin, so that it can include all kinds of crop genes have been found. He called it 12 centers of origin for the large genome centers namely: ① China - Japan Center; ② Southeast Asia Center; ③ Australian Centre; ④ Indian Center; ⑤ in Asia Center; ⑥ West Asia Center; ⑦ center of the Mediterranean; ⑧ Africa Centre; ⑨ Europe - Siberia center; ⑩ South Centre; center of Central America and Mexico; North American centers (Figure 2). Chak Man, also known as the Dutch ac diverse regional variations of these centers, centers or large gene mutation regions including crop diversification native place of origin and place of secondary origin. Although some centers in the country named, but its scope but not in border regions to the origin of the distribution is based on the type of crop diversification.
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zuowu qiyuan zhongxin xueshuo Centers of crop origin theory theory of centers of origin of crops Presented by the Soviet botanists and agronomists Н.И. Vavilov. He cultivated plant species on the planet according to the unbalanced distribution of the species abundant, there is a lot of variation in several areas designated as centers of crop origin. Doctrine of the origin of the problem of the formation of early crops for people to attention. But the modern scientific method to explore the origins of crops, began in the Swiss botanist A. de worthy and more. He kinship plant taxonomy and plant geography natural viewpoint crop research, historical and geographical distribution flora, applied archaeological research unearthed the remains of plants and plant cave drawing images, and applications paleontology, history and Verify the location of the origin of crop knowledge of linguistics, first proposed the initial human domestication of plants in the region may be China, southwest Asia and Egypt to tropical Africa, 3, and published the famous "origin of cultivated plants," a book in 1882. Limited to conditions at that time, although the book is not sufficient data and the lack of basic cytogenetics, but there are still major problems of crop origin reference value. Vavilov was under German influence began to engage more worthy of study of the origin of the crop. From 1920 onwards, he has organized a large-scale plant collecting expedition team has visited more than 60 countries, the ecological environment in different regions for nearly 200 visits, collected more than 30 million copies of their crops Relatives relatives specimens and seeds. In the system subsequent collation and analysis of the study, in addition to his application Linnaean nomenclature to classify, but also choose some important crops, by morphology, cytology, genetics, immunology and determination of ability to adapt to the environment, Identification of some of the crop of new subspecies and new variants. On this basis, he was observed by the geographic distribution of these distinguishing species and varieties from the map, which found that the variation of species diversity in the distribution of imbalance, the formation of centers of crop origin concept. The main content of Vavilov believes there are two main centers of origin of crop characteristics: high genetic diversity and dominant gene frequencies, it can be called the gene mutation center or center of diversity. The origin of the most original native origin center. When the crop thus spread to the edge of a range of locations will result in the crop itself and the natural self-isolation and diverse region formed by the new recessive gene, that secondary centers of origin or secondary gene center. In addition, he also found in certain ecological environment, annual herbaceous crops there is a similarity between the parallel phenomenon of genetic variation in traits such as gramineous and leguminous crops in the Mediterranean region showed no exception, lush plants, spike Big tablets, sub-pale, high-yielding disease; while China is the development of short-term crops, plant dwarf, small grain, fast post-grouting, mostly non-awn or awn hook (refer to wheat). He called this phenomenon "the law of homologous series of genetic variability." Vavilov domesticated according to sources, the crop is divided into two categories, one is the purpose of human domestication of plants, such as wheat, barley, corn, cotton, etc., called native crops; the other is associated with native crops weed, when it is propagated to unsuitable for crops and native environment suitable for their growth and have a definite value when it was separated from the human body and become cultivated such crops called secondary crops. Such as oats and rye in the Central and Western Asia are mixed in the raw wheat, barley weeds, while further north due to the cold strong local cultivation of wheat and barley, it was separated out into secondary crops. 1926 Vavilov made at least view Southwest Asia (in Asia), the Mediterranean region, Southeast Asia and tropical America plateau four world centers of crop origin. Later, with the expansion of the scope of the inspection area for further analysis and study materials, and asked the following eight centers of crop origin (Fig. 1 Vavilov proposed eight centers of crop origin) in 1935: ① China - East Asia; ② India - Tropical Asia, including Malaya complementary areas; ③ Central Asia; ⑤ Mediterranean coast and adjacent areas;; western Asia ④ ⑥ Ethiopia; ⑦ southern Mexico and Central America; ⑧ South America, including Peru, Ecuador, Bolivia and Chile Qi Luoai Island supplementary area. He believes this eight centers in ancient times due to the mountains, the desert or the sea barrier, which is independent of the development of agriculture, the use of tools, draft animals, cultivation methods vary, each center has a considerable number of valuable crops and diverse of variation, crop breeders seek treasure trove of new genes.