In his expeditions, Vavilov collected a rich collection of cultivated plants, found family connections between them, and predicted the previously unknown but genetically inherent properties of these crops that could be bred. He discovered the existence of areas with the maximum concentration of species, varieties and varieties of certain cultivated plants, and also that these areas are associated with the sites of ancient civilizations.
During the research N.I. Vavilov identified seven main geographical centers of origin of cultivated plants.
1. The South Asian tropical center (Fig. 2) includes tropical India, Indochina, South China, and Southeast Asia. Cultivated plants of the center: rice, sugar cane, cucumber, eggplant, citrus fruits, mango, banana, coconut palm, black pepper - about 33% of all cultivated plants.
Rice. 2. South Asian tropical center ()
2. East Asian center - Central and Eastern China, Japan, Korea, Taiwan (Fig. 3). From here came soybeans, millet, buckwheat, plums, cherries, radishes, Walnut, tangerine, persimmon, bamboo, ginseng - about 20% of cultivated plants.
Rice. 3. East Asian center ()
3. South-West Asian center - Asia Minor, Central Asia, Iran, Afghanistan, South-West India (Fig. 4). This center is the progenitor of wheat, barley, rye, hazelnuts, legumes, flax, hemp, turnips, garlic, grapes, apricots, pears, melons - about 14% of all cultivated plants.
Rice. 4. South-West Asian center ()
4. Mediterranean center- countries on the Mediterranean coast (Fig. 5). From here came cabbage, sugar beets, olives, clover, lentils, oats, flax, bay, zucchini, parsley, celery, grapes, peas, beans, carrots, mint, cumin, horseradish, dill - about 11% of cultivated plants.
Rice. 5. Mediterranean center ()
5. Abyssinian, or African center - the Abyssinian highlands of Africa in the region of Ethiopia (Fig. 6). Wheat, barley, sorghum, coffee, bananas, sesame, watermelon - about 4% of cultivated plants - originated from there.
Rice. 6. Abyssinian, or African center ()
6. Central American center - Southern Mexico (Fig. 7). The ancestor of beans, corn, sunflower, cotton, cocoa, pumpkin, tobacco, Jerusalem artichoke, papaya - about 10% of cultivated plants.
Rice. 7. Central American Center ()
7. South American, or Andean center - the western coast of South America (Fig. 8). From this center came the potato, tomato, pineapple, Bell pepper, cinchona tree, coca bush, hevea, peanuts - about 8% of cultivated plants.
Rice. 8. South American, or Andean center ()
We got acquainted with the most important centers of origin of cultivated plants; they are associated not only with floristic wealth, but also with ancient civilizations.
Bibliography
- Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - Bustard, 2009.
- Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of general biology. 9th grade: Textbook for 9th grade students of general education institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.
- Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology: Textbook for grade 9, 3rd ed., stereotype. - M.: Bustard, 2002.
- Dic.academic.ru ().
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- Biofile.ru ().
- Who formulated a complete theory of the centers of origin of cultivated plant species?
- What are the main geographic centers of origin of cultivated plants?
- What are the centers of origin of cultivated plants associated with?
A. S. Konkov
It is obvious that cultivated plants appeared in nature not by themselves, but with the participation of humans on the basis of some wild forms. This is supported by the fact that cultivated plants often have properties that are useful for humans, but not at all useful for the plants themselves in the wild. Such a quality, for example, is the inability to shed seeds in many cultivated cereals. Many qualities in cultivated plants are clearly hypertrophied - for example, the pulp of fruits is too thick garden plants- and are unnecessary for existence in the wild. As a result, many (though not all) crop plants die or are quickly replaced by other species in natural habitats.
In addition, crops are not necessarily grown in the same places where they were originally domesticated. According to modern estimates, approximately 70% of cultivated crops that provide food for the local population are grown outside their original homeland.
How did the domestication of the wild progenitors of cultivated plants occur? Were such centers of origin of cultivated plants concentrated in narrow zones, or did their domestication occur over a wide area? If the zones of origin of cultivated plants were territorially limited, were there many narrow local foci independent for each individual plant or could they unite entire complexes of potential domesticated species? Well, a particularly intriguing question is whether the botanical advantages of individual localities could provide some advantage to local societies, stimulating their social development? Could they, for example, have contributed to such phenomena as the Neolithic revolution described by? It is absolutely possible that this process and similar processes in other regions of the world began their spread precisely from places that were more fortunate than others with potential domesticates in the local flora.
The first researcher who tried to answer these questions was the Swiss botanist Alphonse Louis Decandolle. He established putative geographic zones of origin for individual cultivated plants from their wild relatives. Decandolle revealed a multiplicity of such centers. He combined these studies in a large work, “Origine des plantes cultivées.” However, Louis Decandolle believed that all differences in the ancestral homeland of origin of individual cultivated plants can be explained only by two reasons: 1) climatic zonation 2) differences in the set of species in different floristic regions and provinces (which arises due to the long-term geological isolation of these areas from each other ). In the first case different plants come from different adaptation zones. In the second case, different groups of plants arose during the long isolation and independent evolution of individual floristic regions over many millions of years. Decandolle's research denied the existence of any narrow local foci of domestication. He believed that the zones of domestication of wild progenitors of agricultural plants covered wide areas.
Map of the Earth's natural zones
Map of the Earth's floristic regions
The first researcher who tried to answer these questions was the Swiss botanist Alphonse Louis Decandolle. He established putative geographic zones of origin for individual cultivated plants. Decandolle revealed a multiplicity of such centers. He combined these studies in a large work, “Origine des plantes cultivées” (“Origins of cultivated plants”). However, Decandolle believed that all differences in the ancestral homeland of origin of individual cultivated plants can be explained by only two reasons: climatic zonation and differences in the set of species in different floristic regions and provinces (which arises due to the long-term geological isolation of these areas from each other). In the first case, different plants come from different adaptation zones. In the second case, different groups of plants arose during the long isolation and independent evolution of individual floristic regions over many millions of years. Decandolle's research denied the existence of any narrow local foci of domestication. He believed that the zones of domestication of wild progenitors of agricultural plants covered wide areas.
The indisputable merits of Decandolle are that he found the approximate origins of many species (albeit within wide geographical boundaries), and that he postulated the very idea of the multiplicity of such areas of selection of different cultivated plants. But a real revolution in views on the nature of the origin of cultivated plants was carried out by our compatriot, the outstanding geneticist of the 20th century, Nikolai Ivanovich Vavilov. Having made about 180 expeditions to different parts of the world, Vavilov established that climatic reasons and floristic division are far from the only factors that determined the history of the emergence of cultivated plants. In the world flora there are selection bundles that unite entire complexes of species responsive to selection. Moreover, within these zones, not 1-2 species are concentrated, but a whole palette of potential domesticates and wild relatives of cultivated plants, and the number of these centers is limited. When new places were settled, secondary foci with their own could arise. unique varieties and cultures, but the initial impulse came precisely from the primary centers. From there the very spread of the productive economy and the most important food crops began. And this happened due to the fact that the centers of origin of plants were not just centers of speciation and variety formation, but also centers of particularly high diversity of the ancestors of cultivated plants (i.e., species responsive to human selection).
Initially, Nikolai Ivanovich Vavilov identified 7 primary geographic centers of origin of cultivated plants [Vavilov 1939].
4 centers are located in Eurasia :
- South Asian Tropical Center
(rice, sugar cane, citrus fruits, cucumber, mango, eggplant, black pepper).
- East Asian Center
(soybeans, buckwheat, millet, chumise, radish, cherries, plums)
- South West Asian Center
(wheat, rye, barley, figs, pomegranate, quince, cherry, almonds, sainfoin)
- Mediterranean center
(olive Tree, cabbage, mustard, carrots)
1 center is located in Sub-Saharan Africa :
- Abyssinian center
(teff, coffee, watermelon)
2 independent centers are located in the New World:
- Central American Center
(corn, beans, avocado, cocoa, tobacco)
- Andean (South American) center
(potatoes, pineapple, quinoa, tomatoes)
In Australia no primary center of plant origin arose.
Centers of origin of cultivated plants, originally identified by N. I. Vavilov
After the appearance of new data, Vavilov’s students E.N. Sinskaya and P.M. Zhukovsky not only clarified the history and geography of secondary centers, but also identified new primary centers, and some old foci, which in earlier studies seemed to be single, were separated. Thus, the South-West Asian center was divided into the Western Asian and Central Asian, and the South Asian tropical center split into the Hindustan center, located in India, and the Indo-Malayan center, associated with the countries of Indochina and the islands of Indonesia. As a result, the list of primary centers increased to 12 in Zhukovsky and 10 (included in 5 large communities) in Sinskaya. It should be noted that Vavilov himself hesitated regarding the need to single out the Indochina and Central Asian centers as independent centers of domestication.
Over time, thanks to the work of foreign researchers, special independent centers of plant domestication, different from Ethiopian, were discovered in Africa in the western part of the Dark Continent. An independent primary focus of selection was also found in North America. Perhaps a separate center of domestication, different from the Andean one, existed in the Amazon basin. A center for the domestication of agricultural plants, isolated from the rest of the world, was also discovered in New Guinea, the influence of which remained limited to the small area of \u200b\u200bthis island and had little impact on other regions of the World except Melanesia.
Centers of plant origin in Western Eurasia
Western Asian early agricultural center - the most ancient of all hearths in the world. Its territory included Asia Minor, the Levant, the Zagros Mountains in the Iran-Iraq borderland, and Transcaucasia. The transition to a productive economy took place here in the 9th–7th millennium BC. e. Wheat, barley, rye, lentils, figs, pomegranate, quince, and almonds were developed here.
The domestication zone covers territories with a precipitation rate of 300–500 mm per year in the foothill zone of local uplands and approximately corresponds to the zone of oak-pistachio forest-steppe. However, wild barley and some legumes are found in a drier zone with a rainfall rate of 200 mm per year, extending into the steppe regions of the plain. For the wild Central Asian ancestors of cultivated cereals, in addition to the general norm of moisture, their confinement to a certain time, namely the winter season, which should precede their ripening in the spring, is very important. After the rainy period, wild cereals produce abundant thickets, where up to 2 kg of grain per hour can be collected by hand, which should have provided an incentive to collect these cereals. This may be why legume remains are very rare in Early Neolithic paleobotanical collections.
A single Central Asian center arose due to the merger of 5-6 local microcenters into one. These include Eastern Mediterranean (Palestine, Southwestern Syria), North Syriac , southeastern Anatolian , Southern Anatolian , Zagrosian(from Northern Iraq to Southwestern Iran), Transcaucasian microfoci.
- IN Eastern Mediterranean In the microfocus, emmer and two-row barley were domesticated, and lentils and peas were domesticated from legumes.
IN North Syrian in the outbreak - einkorn wheat, barley, and also, as in the first outbreak, lentils and peas.
IN southeast Anatolian local varieties of emmer and einkorn wheat, lentils and peas are at the hearth.
IN Zagros microfocus - its own varieties of einkorn wheat, emmer, two-row barley, but this center is distinguished by the low role of legumes.
IN South Anatolian - einkorn wheat, barley and lentils, peas, chickpeas, chickpeas. Rye was domesticated here.
IN Transcaucasian- local varieties of millet and wheat.
The last two lesions may be secondary, but this issue requires additional research. The completion of the formation of a single Central Asian focus caused a new stage of selection, when multi-row barley and tetraploid and hexaploid wheat were bred in the Middle Eastern region.
Habitats of wild relatives of cereals in Western Asia
The influence of the Central Asian focus not only had a huge impact on a significant part of the Old World - it contributed to the emergence of secondary centers based on the cultures of this center in Western and Eastern Europe, North Africa, Arabia, the Caucasus, Iran, Central Asia and Northern India. It was from this region that the Neolithic revolution in Western Eurasia began. And although, of course, it would be wrong to reduce all its causes solely to geobotany factors, there is no doubt that the advantages of the local flora played a significant role.
Interesting connections between the Western Asian center and Mediterranean center . Of the local cereals, only oats were domesticated here. But the local flora provided many new domesticates, generating enormous wealth vegetable crops: radishes, cabbage, parsnips, mustard, carrots, carob and olive. Despite this, modern evidence suggests that agriculture did not originate here independently, but under the influence of the Middle Eastern impulse. Middle Eastern crops became the basis of food here, and the selection of local crops itself was initiated and stimulated by Middle Eastern influence. Vavilov included in the area of the Mediterranean focus some western parts of the Western Asian focus, suggesting that they could be genetically related to the more western centers of Europe, while the more eastern regions of the Western Asian focus, including the Levant, were initially isolated from the history of Mediterranean agriculture. One of key differences between the Mediterranean and Western Asian centers, he considered different shapes wheat: independent selection in the Mediterranean focus led to the emergence of large-seeded tetraploid varieties of wheat, in the Western Asian focus - small-seeded hexaploid varieties. However, modern genetic data indicate that these processes were more complex. Probably, the Levantine center of domestication should be considered simply as part of the Western Asian center. And all domestication centers in Europe and North Africa are like its secondary daughter centers. Therefore, although this goes against Vavilov’s original scheme, the Mediterranean center must be excluded from the primary zones of origin of cultivated plants.
Central Asian outbreak
It is distinguished by a very high diversity of agricultural plant varieties, which makes its identification as an independent center justified. It occupies the territory from Turkmenistan to the Indus basin and from Badakhshan to Iran. Here, during selection, local farmers developed local varieties of wheat, pears, and apricots. Over time, part of the eastern part also came here. Asian plants, which led to the emergence of local varieties of persimmons and plums. The origin of this center dates back to the 6th millennium BC. e. However, the Central Asian center is secondary and is derived from the Western Asian one, since most of the local cultivated plants come from Middle Eastern cultures. Probably, the spread of agriculture here began from the south of the region - from Southern Afghanistan and Balochistan. In the north, in modern Turkmenistan and Central Asia, the productive economy appears later. Also, the Central Asian center undoubtedly includes Northwestern India, where, based on Middle Eastern crops, a special variety of round grain wheat was developed, which became the basis crop in local irrigated agriculture.
Centers of plant origin in South Asia
The origin of most of the cultivated crops is traditionally associated with this region. The center of domestication is located in the mountainous regions of the Indochina Peninsula, Southern China south of the Yangtze River and the northeastern part of Hindustan. Rice, sugar cane, bananas, citrus fruits, durian, taro, eggplant and most of the plants that are sources of classical spices were introduced here.
In the territory Hindustan agriculture is secondary to other regions. The local flora provided a certain number of cultivated plants, but Indian domesticates played a supporting role and did not become the main livelihood of the societies of this region. These include mung bean and cucumber. The origins of agriculture and most crops in India are linked to other regions of Eurasia and even Sub-Saharan Africa. In the first half of the 2nd millennium BC. e. Millet, barley, wheat, and flax entered India, clearly coming here from Western Asia. Rice penetrated from the Indo-Malayan center to Hindustan (it was found back in the period of the Harrapan civilization). And from Africa, bypassing the Middle East (apparently through South Arabia) - sorghum, dagussa, lobia. These crops became the basis of agriculture on the Deccan Plateau.
Indo-Malay Center , on the contrary, played main role in domestication and selection of ancestors of cultivated plants. Initially, this region was considered as a periphery, into whose territory agriculture and domesticates spread from other centers. Vavilov was one of the first to change his mind about the local flora and appreciate its enormous potential. However, he included it only as a local center very rich in species within the general South Asian center, along with the Hindustan. Later botanical studies not only confirmed, but also strengthened the view of the richness and diversity of wild and cultivated flora of Indochina, southern China and northeastern India. Therefore, it is advisable to present the Indo-Malayan center as the primary center of plant domestication in South Asia, and consider the Hindustan and local centers of domestication in Indonesia as its derivative centers.
The main crops of the Indo-Malayan center, which played a special role in the development of local agriculture and agriculture in other regions, were rice, taro and South Asian forms of yam.
Taro and Asian forms of yam are starchy tubers that are analogues of similar crops in other parts of the world: sweet potato, potato and cassava in the New World and African yam on the Dark Continent. The advantages of taro are its greater unpretentiousness, the disadvantage is its lower yield and its requirement for very high humidity. It can only be cultivated where the annual rainfall ranges from 1000 to 5000 mm per year. The advantages of yam are its higher yield, less demanding on moisture, the disadvantages are the short harvest period and the greater capriciousness of this crop. Probably, yam was introduced into culture after taro and by those groups of the population that already had the skills of selection and agriculture.
Rice domestication occurred in the north of the Indochina Peninsula, including certain territories of Northeast India and the extreme south of China. This is where the wild relatives of rice (Oryza rufipogon, Oryza nivara) live. Cultivated rice has two main, most common varieties: Indian rice (Oryza sativa indica) with long and non-sticky grains and Japanese rice (Oryza sativa japonica) with short and sticky grains. Japanese rice is more frost-resistant, which has allowed this variety to spread to the mountainous regions of Southeast Asia and India, as well as to more late time- V temperate climate Korea, Japan and Northern China
Because these varieties are so markedly different morphologically that crossing between them is difficult (which is rare in plants even in the case of interspecific hybridization), it has even been assumed that they were domesticated in different regions. But geneticists have determined that all cultivated forms of rice originated from a single ancestor approximately 8,200 thousand years ago in the region south of the Yangtze River, and the separation of Japanese and Indian rice occurred 3,900 years ago. In the Ganges and Yellow River valleys, rice culture is secondary and appears late. The sterility of hybrids between these subspecies is not associated with any systematic distance, but with an imbalance in the functioning of genes that inhibit programmed cell death - apoptosis in the ovules, which causes seed sterility.
Rice cultivation area
Rice is a hydrophilic plant that requires high humidity of 1000 mm per year, so the introduction of rice into the culture could only take place in a humid zone.
Rice also has dry-land varieties, which are cultivated in the highlands far from rivers and allow it to be grown without the use of irrigation. However, botanical data indicate that these varieties are secondary, have a later origin and cannot be primitive forms. When breeding rice, as well as when breeding wheat and corn, in order to transform it from a wild form into a cultivated one, it was important that the seeds did not fall off on their own, because this made it possible to preserve the harvest. It is curious that the change in this trait was associated with a mutation in only one gene, sh4, which triggers the entire process of formation of the separating layer on the stalk. Perhaps for this reason, the domestication of rice occurred faster and was less extended over time than that of wheat.
The general history of the formation of the Indo-Malay center of domestication and the emergence of a productive economy suggests several scenarios. Some authors believe that agriculture initially arose on the basis of the cultivation of tubers such as taro and yams, and only at the next stage there was a transition to intensive rice cultivation. This point of view seems more plausible, but one must also take into account alternative hypotheses, according to which rice could have been introduced into culture before tubers. A special view on the origin of the productive economy in Southeast Asia belongs to Soer. According to his model of domestication, in this region the domestication initially began not of purely food species, but of plants of multifunctional use (such as pandanus, cordiline). Other crops gradually entered the economy as accompanying crops and already at the next stage, after a certain selection, took a central place in the structure of life support. It is difficult to say which of these hypotheses is more plausible, but agriculture in Southeast Asia most likely arose among semi-sedentary fishermen who cultivated moisture-loving crops near their villages. Considering that the relatives of some of the plants (sago, taro, banana) should have been domesticated in the zone of very humid tropics, and others (yam, sugar cane) in zones of monsoon climate, allowing alternation of drier and wetter seasons, it is obvious that here , as well as in Western Asia, the center of domestication developed due to the merger of several territorially close micro-foci].
Impulses from the primary Indo-Malayan center led to the emergence of secondary foci in India, the islands of Indonesia and Taiwan. From these last two centers, plants bred in the Southeast Asian center spread to the island of Madagascar, as well as to Polynesia and other islands of the Pacific Ocean, creating the basis of agriculture in Oceania.
It is characteristic that while tropical tuber crops spread to the south and southeast, rice primarily spread to the west and north.
Centers of plant origin in East Asia
East Asian Primary Center located in Northern China in the middle reaches of the Yellow River. The basis of its agriculture before rice penetrated here from the south was chumiza. Asian millet, daikon radish, plum, persimmon and a number of other crops were also domesticated here. Vavilov assumed that the core of this center was closer to the Yangtze basin. But according to modern ideas, the Yangtze basin is included in the area of the Indo-Malayan center.
It is interesting that the local agricultural complex was actively supplemented by introduced crops, i.e., new crops from the Indo-Malayan and Central Asian focus (such as wheat and rice) during the period when the transition to a productive economy not only ended in the Yellow River basin, but also a developed statehood had already emerged (in the 2nd millennium BC). This significantly distinguishes these processes from those that took place in the Indo-Malayan region, where, on the contrary, the state did not emerge for a long time even after the transition to developed agriculture.
Based on the East Asian primary center, it was formed Korean-Japanese secondary outbreak , where, in addition to East Asian plants and rice, some new crops from the local flora were domesticated, such as native varieties of yam (Dioscorea japonica).
Centers of Plant Origin in America
On the North American continent, in the mountainous regions of Mexico, a Central American Center . In it, corn, beans, amaranth, and pumpkin were introduced into the culture. Probably, here, as in the Western Asian center, a merger of several local microfoci occurred. Interesting feature In this center there was an unusually long transition to stable agriculture. If its beginnings arose only a little later than in the earliest centers of the Old World - in the 9th millennium BC. e. - then its final formation occurred only in the 3rd - 2nd millennium BC. e. The reasons explaining this slow transition require explanation in future research.
Soon after, the production economy and its accompanying domesticates began to spread into the lowlands of Mexico and Central America, and then expanded into the United States. A very large subsidiary arose here Arizona-Sonora focus .
It is interesting that in the eastern USA in the 2nd - 1st millennium BC. e. its independent center of domestication began to take shape, which was based on the cultivation of cyclachena, canary grass, knotweed and goosefoot. However, its small initial set of species prevented it from becoming a major center. And local plants in the 1st - early 2nd millennium AD. e. were displaced by Central American domesticates, forming a secondary focus - Alabama-Illinois .
Range of wild relatives of cultivated plants in North America
On the South American continent, in the Andes mountain zone, it formed South American (Andean) center . Potatoes, pineapple, quinoa, and tomatoes were domesticated here. There was a very clear vertical zoning in the development and selection of ancestral species of agricultural plants. Domestication of potatoes and quinoa took place in the high-mountain zone, and pumpkins and legumes in the middle mountains. This center developed in the 3rd - 2nd millennium BC. e. Corn introduced from the Central American center provided a great stimulus for the development of local agriculture.
On the coast of South America, during the transition to agriculture in the mountainous regions, intensive fishing dominated, and the appropriating economy did not immediately give up its position to the producing one. However, it gradually fell into the sphere of influence of the mountain zone, cultivated plants from the Andes zone spread here and its secondary focus was formed.
The situation with the cultivation of cassava, which is grown by many peoples of the Amazon and Orinoco basins, is somewhat less clear. It is widely believed that it could have arisen under the influence of Andean agriculture in the foothill zone, transitional to the jungle. However, this assumption requires proof, and the possibility of an independent origin of this focus in the Amazon cannot be ruled out.
Range of wild relatives of cultivated plants in South America
Centers of plant origin in Africa
Several centers of primary domestication arose in Africa. Vavilov connected the origin of agriculture and the domestication of African cultures with the Ethiopian Highlands. It is now clear that there were also other centers for the selection of the ancestors of cultivated plants in the west of the continent. But with regard to the Ethiopian center, some authors assume that its initial formation was not with the mountainous regions, but rather with the adjacent regions of the Sahara, from where these cultures later spread to the highland zone.
Porter identified several centers of plant domestication in Sub-Saharan Africa:
- Nilo-Abyssinian , corresponding to the Vavilov Ethiopian Center,
- West African
- East African
- Central African.
Due to this problem, the American botanist Harlan proposed a special model of domestication for Africa, where narrow local centers do not exist. According to his concept, various plant species were cultivated here in a variety of places, often quite distant from each other, but then a single communication network for the exchange of cultivated plants united remote regions of this continent. To describe it, he created the term “uncenter”. A number of Soviet researchers demonstrated similar views and viewed all of Africa as a single global non-localized macroarea of plant domestication.
And yet, despite the unclear boundaries and wide areas of domestication of many local species, several zones can be distinguished in Africa, corresponding to cultural centers in other regions. First outbreak associated with the cultivation of African cereals and associated with the savannah zone that extends south of the Sahara between Senegal and the Nile Valley. Sorghum, pearl millet and African rice were domesticated here. Second outbreak associated with the cultivation of African yams in the border forest zone; oil palm and kola nut were also domesticated here. It is possible that the second center could have arisen under the influence of the first, and together they form a single West African center. Third center occupies the mountainous regions of Ethiopia and/or the lowland regions of the Sahel close to it. Teff, dagussa, ensette, watermelon and coffee were domesticated here.
Under the influence of the Ethiopian and West African macrofoci, subsidiary centers appeared in East and Central Africa.
Unlike animal husbandry, Middle Eastern domestication has had a limited impact on the range of crops grown in Sub-Saharan Africa, except in some areas in Northeast Africa. This is due to the fact that the ancestors of many Central Asian plants were domesticated in the winter rainy zone and are not suitable for African agriculture, which requires adaptation to the summer rainy season. It is interesting that in those areas of Eurasia where there is a zone of summer rains (as on the Deccan Plateau), on the contrary, there was an active development and introduction of African crops: dagussa, lobia, pearl millet. Since this spread bypassed the countries of the Levant, the Fertile Crescent and Iran, then mediation in the spread of African cultures should be associated with South Arabia.
Range of wild relatives of cultivated plants in Africa
Domestication in Oceania
A significant part of the cultivated plants in Oceania is of Asian origin (mainly from the Indo-Malayan focus). And on Easter Island even American influence is allowed due to the presence of American varieties of sweet potatoes and gourds.
For a long time it was believed that agriculture was brought to the Pacific Islands entirely from outside and arose here along with the emergence of the archaeological Lapita culture, which is associated with the first groups of Proto-Polynesians. The ancestors of the Polynesians actually brought many agricultural plants from Asia to Oceania. But due to the fact that this population group was the first to begin developing the marginal islands of the Pacific Ocean, which had not previously been inhabited by humans, it is quite natural that plants from Asian centers of domestication predominate in a significant part of the archipelagos of this region. However, recently, a lot of evidence has accumulated that some farming skills could have arisen in this region without the influence of cultural innovations brought by Polynesian migrants from Asia. Thus, local varieties of sago, breadfruit, yam, and sugar cane were domesticated independently in New Guinea. There are somewhat contradictory data on the domestication of the Oceanic variety of taro, which could have been domesticated either independently or brought from the Indo-Malayan center. Archaeological evidence is in agreement with these data. In the mountainous regions of New Guinea (in Kaviafana), traces of irrigation or drainage canals were discovered that date back to the 9th millennium BC. e. According to palynological analysis, reliable traces of plant cultivation date back to the middle of the 2nd millennium BC. e. But one way or another, New Guinea actually had its own narrow local focus of primary domestication, which appeared completely independently of other centers.
New Guinea Center - the only center of primary domestication in the world ecumene that did not have any large-scale impact on other regions of the world (it had a limited impact only through a series of borrowings on some islands of Melanesia) and remained within a narrow zone of its ancestral home. But apparently this exceptional fact can be explained by several simple reasons. Agriculture originated here within a very large island (the second largest in the world after Greenland), which has a high diversity of landscapes. Domestication took place within a large mountainous region in its center, which was limited from the coast, which retarded influences from the interior of the island to the outside world and, conversely, inhibited influences from the outside world to the interior of the island. At the moment when agriculture was fully developed in the interior of New Guinea, it was actively spreading from Asia to other regions of Oceania. Therefore, just as New Guinea agriculture could not displace Asian agriculture on other islands, so Asian agriculture was not able to displace New Guinea agriculture. The domestication of cultivated plants in the New Guinea center occurred on the basis of species taxonomically close to the species of the Indo-Malayan center (sago, yam, breadfruit), therefore neither New Guinea nor Indo-Malayan domesticates had an advantage over each other for borrowing (except, perhaps, taro) . Because of this, it was advisable to use ready-made complexes of cultivated plants, independently developed in New Guinea and the Indo-Malayan center.
Distribution of Asian plants along with Polynesian migrations
Conclusion
Now, approximately a century after the appearance of the first results in Vavilov’s largest study, it is clear that his theory and views on the origin of cultivated plants are correct, although significant adjustments have been made to his original scheme for identifying the basic primary centers. Without a doubt, agriculture originated not in one, but in several independent centers of origin of cultivated plants. Therefore, any monocentric theories are untenable. Domestication and selection of wild progenitors occurred in relatively narrow zones that united entire complexes of such species.
Modern ideas about the primary centers of domestication of cultivated plants
and their distribution to other regions
The earliest ancient center of origin of cultivated plants, which arose earlier than all the others, is the Western Asian center, which was formed as a result of the unification of several local microfoci.
The existence of the Mediterranean Center as a center in its own right needs to be reconsidered. Its eastern Syro-Palestinian part can be considered as one of the centers that merged into the Near Asian center, and it is appropriate to consider it as part of the Near Asian center of domestication. The western regions, associated with the Balkans and the western Mediterranean, are undoubtedly secondary centers that were formed during the spread of agriculture from the Central Asian center to Southern Europe. However, the local flora also provided excellent material for selection, and under the influence of the Middle Eastern impulse, a considerable number of native plants.
The Central Asian center, like the Mediterranean center, is secondary. It arose on the basis of Middle Eastern cultures, which spread from the Central Asian center to the east. This secondary center, in addition to Iran and the southern regions of Central Asia, also covered the western part of Hindustan in the Indus Valley.
Views on the development of agriculture and domestication in South Asia also need to be reconsidered. The original centers of South Asian agriculture and domestication of local plants are not in India, but in Indochina. Indian agriculture arose due to the joint influence of the Western Asian and Indo-Malayan centers and African centers of agriculture. In Hindustan itself, not many species of local flora were domesticated, and the Hindustan center must be considered secondary. The Indo-Malay center, on the contrary, is clearly the primary center. In the past, it was he who was the main incubator for the domestication of South Asian plants. It is especially interesting that, despite the antiquity of this center and the exceptional wealth of agricultural crops, in the zone of the Indomalayan center, unlike many other primary and secondary centers, state formations and urban civilizations arose very late, which in some ways makes this situation similar to the one seen in America.
The East Asian center, together with the Western Asian and Indo-Malayan ones, is the third basic primary center of Eurasia, where, unlike the Mediterranean, Hindustan and Central Asia, agriculture arose independently without any outside influence. Modern data localize the geographic location of this center in the Yellow River basin, i.e., further north than Vavilov assumed.
In Africa, agriculture developed in the most unique and different way in comparison with other continents. There were several initially isolated, but early united centers, geographically distant from each other (which distinguishes it from the Middle Eastern focus, where such proto-centers are located closely): in Ethiopia, the Western Sahel and the tropics of West Africa. It is possible that a global sub-Saharan network of diffuse interconnected microcenters could have arisen here, which united into one broad community, forming a pan-African non-localized focus. This unique feature of this region. But he draws attention to the fact that in Africa, as in other regions, the zones of domestication of many plants gravitate either to mountainous areas (in Ethiopia, the Guinea Mountains), or in the rugged terrain of the borders between different biotopes: savannas and semi-deserts, savannas and tropical forests, which in West Africa are close to each other. And here the cores of domestication in the Sahel, the Ethiopian Highlands and Guinea are still identified. But of course, a thorough study of the zones of domestication of cultivated plants in Africa is still waiting in the wings.
Three primary centers arose in the New World. Two of them, Andean in South America and Central American in North America, became important, influencing neighboring regions of North, Central and South America. Both of these centers had a limited influence on each other. The third center of domestication of the New World - Eastern North American - was not identified by Vavilov. But this center, although it arose completely independently, was not rich in potential domesticates, and was eventually absorbed by cultures from subsidiary secondary centers derived from the primary Central American center. With regard to the Amazonian center, it is not yet very clear how independent it is, whether it arose as a primary center or as a secondary center on the periphery of the Andean. An important feature of the development of the New World is that here, unlike Eurasia and Africa, the development of agriculture did not lead to bright “Neolithic revolutions” and the process of transition to more complex societies here, unlike the Old World, was slowed down.
In Oceania, New Guinea, an independent center for the domestication of agricultural plants arose, isolated from the rest of the world, where agriculture arose independently, but remained locked within a limited territory.
It is very important that all the primary centers of origin of cultivated plants identified by Vavilov, and most of the newly identified centers, are confined to mountainous regions of the subtropical and tropical zone. This is due to the wide variety in mountain landscapes, which create very wide range adaptations to completely different conditions within a nearby territory, and also create structured populations with high level drift in subpopulations, which also contributes to the emergence and spread of rare variants. In some cases, as in West Africa and in the Yellow River Valley, the clear pattern of linking the origin of cultivated plants to mountainous regions is still violated. However, here too, domestication occurred in the border zone of very different and dissimilar ecosystems, contributing to population diversity. Therefore, here the diversity of domesticates was influenced by the same reasons as in mountainous areas.
How the diversity of species responsive to selection has influenced the social and demographic advantages of their populations, and what genetic data can tell us about this, will be discussed in a future publication.
Bibliography
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Zhukovsky P. M. Cultivated plants and their relatives. Systematics, geography, cytogenetics, ecology, origin, use. 3rd ed. L.: Kolos, 1971. 752 p.
Sinskaya E. N. Historical geography of cultural flora (At the dawn of agriculture). L.: Kolos, 1969. 480 p.
Shnirelman V.V. The emergence of a producing economy. - M.: Nauka, 1989. - 448 p.
Ballard, C., Brown, P., Bourke, R. M., Harwood T. The Sweet Potato in Oceania: A Reappraisal // Oceania Monograph 56/Ethnology Monographs 19. 2005. Sydney: University of Sydney.
Bellwood, P. S. 1979. Man's Conquest of the Pacific: The Prehistory of Southeast Asia and Oceania. New York: Oxford University Press.
Bellwood P. The Prehistory of Oceania // Curr. Anthropol. 1975. T. 16. No. 1. P. 9.
Childe V. G. The Dawn of European Civilization // Am. Hist. Rev. 1926. T. 31. No. 3. P. 499.
Green, R. A range of disciplines support a dual origin for the bottle gourd in the Pacific // J. Polyn. Soc. 2000. Vol. 109. P. 191–198.
Grivet L. et al. A review of recent molecular genetics evidence for sugarcane evolution and domestication // Ethnobot. Res. Appl. 2004. T. 2. No. 0. P. 9–17.
Harlan J. R. Agricultural origin: centers and noncentres // Science. 1971. V. 174. No. 4008. P. 468–474
Khoury C. K., Achicanoy H. A. Origins of food crops connect countries worldwide // Proc. R. Soc. B. 2016. T. 283. pp. 468–74.
Kjær A. et al. Investigation of genetic and morphological variation in the sago palm (Metroxylon sagu; Arecaceae) in Papua New Guinea // Ann. Bot. 2004. T. 94. No. 1. P. 109–117.
Li C., Zhou A., Sang T. Rice Domestication by Reducing Shattering // Science (80-.). 2006. T. 311. No. 5769. P. 1936–1939.
Malapa R. et al. Genetic diversity of the greater yam (Dioscorea alata L.) and relatedness to D. nummularia Lam. and D. transversa Br. as revealed with AFLP markers // Genet. Resour. Crop Evol. 2005. T. 52. No. 7. pp. 919–929.
Molina J. et al. Molecular evidence for a single evolutionary origin of domesticated rice. //Proc. Natl. Acad. Sci. U.S.A. 2011. T. 108. No. 20. P. 8351–6.
Porteres R. Primary cradle of agriculture in the African continent, 1970. Pappers in the African prehistory. 1970. Cambridge.
Smith B. D. Eastern North America as an independent center of plant domestication. //Proc. Natl. Acad. Sci. U.S.A. 2006. Vol. 103. No. 33. pp. 12223–12228.
Spriggs, M. 1984. The Lapite cultural complex: origins, distribution, contemporaries, and successors. In Out of Asia: Peopling the Americas and the Pacific. R. Kirk and E. Szathmary, eds., pp. 202-223. Canberra: The Journal of Pacific History.
Shaw, T. C. 1980. Agricultural origins in Africa. In The Cambridge Encyclopedia of Archaeology. A. Sherratt, ed., pp. 179-184. New York: Crown.
Tanno K.-I., Willcox G. How fast was wild wheat domesticated? // Science. 2006. T. 311. No. 5769. P. 1886.
Yang J. et al. A Killer-Protector System Regulates Both Hybrid Sterility and Segregation Distortion in Rice // Science (80-.). 2012. T. 337. No. 6100. P. 1336–1340.
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In his expeditions, Vavilov collected a rich collection of cultivated plants, found family connections between them, and predicted the previously unknown but genetically inherent properties of these crops that could be bred. He discovered the existence of areas with the maximum concentration of species, varieties and varieties of certain cultivated plants, and also that these areas are associated with the sites of ancient civilizations.
During the research N.I. Vavilov identified seven main geographical centers of origin of cultivated plants.
1. The South Asian tropical center (Fig. 2) includes tropical India, Indochina, South China, and Southeast Asia. Cultivated plants of the center: rice, sugar cane, cucumber, eggplant, citrus fruits, mango, banana, coconut palm, black pepper - about 33% of all cultivated plants.
Rice. 2. South Asian tropical center ()
2. East Asian center - Central and Eastern China, Japan, Korea, Taiwan (Fig. 3). Soybeans, millet, buckwheat, plums, cherries, radishes, walnuts, tangerines, persimmons, bamboo, ginseng - about 20% of cultivated plants - originated from here.
Rice. 3. East Asian center ()
3. South-West Asian center - Asia Minor, Central Asia, Iran, Afghanistan, South-West India (Fig. 4). This center is the progenitor of wheat, barley, rye, hazelnuts, legumes, flax, hemp, turnips, garlic, grapes, apricots, pears, melons - about 14% of all cultivated plants.
Rice. 4. South-West Asian center ()
4. Mediterranean center - countries on the Mediterranean coast (Fig. 5). From here came cabbage, sugar beets, olives, clover, lentils, oats, flax, bay, zucchini, parsley, celery, grapes, peas, beans, carrots, mint, cumin, horseradish, dill - about 11% of cultivated plants.
Rice. 5. Mediterranean center ()
5. Abyssinian, or African center - the Abyssinian highlands of Africa in the region of Ethiopia (Fig. 6). Wheat, barley, sorghum, coffee, bananas, sesame, watermelon - about 4% of cultivated plants - originated from there.
Rice. 6. Abyssinian, or African center ()
6. Central American center - Southern Mexico (Fig. 7). The ancestor of beans, corn, sunflower, cotton, cocoa, pumpkin, tobacco, Jerusalem artichoke, papaya - about 10% of cultivated plants.
Rice. 7. Central American Center ()
7. South American, or Andean center - the western coast of South America (Fig. 8). Potatoes, tomatoes, pineapples, sweet peppers, cinchona, coca bush, hevea, peanuts - about 8% of cultivated plants - originated from this center.
Rice. 8. South American, or Andean center ()
We got acquainted with the most important centers of origin of cultivated plants; they are associated not only with floristic wealth, but also with ancient civilizations.
Bibliography
- Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - Bustard, 2009.
- Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of general biology. 9th grade: Textbook for 9th grade students of general education institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.
- Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology: Textbook for grade 9, 3rd ed., stereotype. - M.: Bustard, 2002.
- Dic.academic.ru ().
- Proznania.ru ().
- Biofile.ru ().
Homework
- Who formulated a complete theory of the centers of origin of cultivated plant species?
- What are the main geographic centers of origin of cultivated plants?
- What are the centers of origin of cultivated plants associated with?
Lesson 1–2. Subject and objectives of selection.
Centers of origin of cultivated plants and domestication of animals Equipment
: portrait of N.I. Vavilova; tables on general biology;
biological objects illustrating the diversity of varieties of cultivated plants and breeds of domestic animals; map of the main geographical centers of origin of cultivated plants.
DURING THE CLASSES
I. Learning new material 1. Subject and objectives of selection Selection– selection, choice) is the science of obtaining new forms of plants, animals and microorganisms with properties valuable to humans. The selection about which N.I. Vavilov said that this “evolution guided by the will of man” is at the same time an art, a science, and a special branch of agriculture.
The result of breeding work is a plant variety, an animal breed, and a strain of microorganisms. Plant variety or animal breed is a collection of individuals of the same species, created as a result of selection and possessing certain morphological, biological, economic characteristics and properties that are inherited.
Purposeful selection work was preceded by a period of domestication of animals and cultivation of plants. The first attempts at domestication were made by people 10–12 thousand years ago, and perhaps even earlier, when large mammals (the main objects of hunting) were destroyed by ancient hunters, and hunting ceased to provide people with sufficient food. The domestic rabbit was domesticated only in the Middle Ages, sugar beets in the 19th century, and mint in the 20th century. As a science, selection finally took shape thanks to the works of Charles Darwin. He analyzed a huge amount of material on the domestication of animals and the introduction of plants into culture and on this basis created the doctrine of artificial selection. Currently, selection is the most important type of practical human activity, the result of which is all the varieties of cultivated plants available today, breeds of domestic animals and strains of beneficial microorganisms.
The scientific basis of modern selection is genetics, in particular such sections as the theory of genes and mutations, the molecular basis of heredity, the doctrine of the role of the environment in the phenotypic manifestation of genetic information, the theory of distant hybridization, environmental genetics, etc. The use of genetic approaches makes it possible to solve the following tasks of modern breeding:
– increasing yield and productivity already existing varieties and breeds;
– development of new varieties and breeds;
– improvement of product quality;
– increasing the resistance of varieties and breeds to diseases;
– increasing the ecological plasticity of varieties and breeds;
– breeding varieties and breeds suitable for mechanized or industrial cultivation and breeding, etc.
2. Centers of origin of cultivated plants
One of the founders of scientific selection, Academician Nikolai Ivanovich Vavilov, believed that in order to successfully solve selection problems, it is necessary to study:
– initial varietal, species and generic diversity of plants and animals;
– the influence of the environment on the development of traits of interest to the breeder;
– hereditary variability;
– patterns of inheritance during hybridization;
– features of the selection process for self-pollinating or cross-pollinating plants.
This allows you to build a strategy and tactics for artificial selection.
Any breeding program begins with the selection of source material. The more diverse it is, the more effective the results will be. The most important section of selection is doctrine of source material
– was actually developed by N.I. Vavilov and described in detail in his work “Centers of Origin of Cultivated Plants”.
Solving the problem of source material, N.I. Vavilov examined many areas of the globe and identified areas with the greatest genetic diversity of cultivated plants and their wild relatives. In 1920–1930 N.I. Vavilov, together with his colleagues, carried out more than 60 expeditions to 54 countries across all inhabited continents, except Australia. The participants in these expeditions - botanists, geneticists, breeders - were real plant hunters. As a result of enormous work, they established important patterns, showing that not all geographical areas have the same diversity of cultivated plants. Different crops have their own centers of diversity, where the largest number of varieties, varieties, and various hereditary deviations are concentrated. These centers of diversity are also areas of origin
cultivars
. Thus, in potatoes, the maximum genetic diversity is noted in South America, in corn - in Mexico, in rice - in China and Japan, in wheat and rye - in Central Asia and Transcaucasia, in barley - in Africa.
Most centers coincide with ancient centers of agriculture. These are mostly not flat, but mountainous areas. Such centers of diversity N.I. Vavilov first counted 8, and in later works reduced their number to 7.
1. South Asian tropical (Indian, or Indonesian-Indochinese).
2. East Asian (Chinese, or Sino-Japanese).
3. South-West Asian (Forward Asian and Central Asian).
4. Mediterranean.E
Started by N.I. Vavilov's work was continued by other botanists. In 1970 P.M. Zhukovsky established 4 more centers: Australian, African, European-Siberian and North American.
Thus, there are currently 11 primary centers of cultivated plants. Along with the discovery of world centers of origin of cultivated plants, N.I. Vavilov and his collaborators collected the world's largest collection of plants, which was concentrated in the established All-Union Institute of Plant Growing (VIR, Leningrad, now St. Petersburg), currently named after N.I. Vavilova. This collection in the form of seed samples is constantly replenished and reproduced in the fields experimental stations
Institute. It is a storehouse of source material that is used by all geneticists and breeders in the country who work with plants.
Map of centers of origin of cultivated plants The world collection of plants is now the largest national treasure, preserved by VIR employees during the siege of Leningrad during the Great Patriotic War Patriotic War . It requires careful treatment and constant replenishment. The VIR collection contains more than 180 thousand specimens, representing 1,740 plant species from all continents of our planet. Among them are more than 39 thousand samples of grains, more than 19 thousand - legumes, almost 30 thousand - corn and cereals, about 4 thousand - tubers, almost 17 thousand - vegetables and melons, more than 11 thousand - fruits And berry crops
, about 2 thousand samples of grapes, over 9 thousand samples of subtropical and ornamental plants.
Of the 250 thousand species of flowering plants, humans use about 3 thousand species for their own purposes, and only 150 species have been introduced into cultivation.
3. Origin of domestic animals and centers of domestication
As evidenced by modern data, the centers of origin of animals and areas of their domestication, or domestication (from lat. domesticus– home), are the territories of ancient civilizations. In the Indonesian-Indochina center, animals that did not form large herds were apparently domesticated for the first time: dogs, pigs, chickens, geese, and ducks. Moreover, the dog, most of whose breeds are descended from the wolf, is one of the most ancient domestic animals.
In Western Asia, it is believed that sheep were domesticated, their ancestors being the wild mouflon sheep. Goats were domesticated in Asia Minor.
Domestication of the aurochs, a now extinct species, probably occurred in several areas of Eurasia. As a result, numerous breeds of cattle arose. The ancestors of the domestic horse, the tarpan, were finally exterminated at the end of the 19th and beginning of the 20th centuries, and were domesticated in the steppes of the Black Sea region. In the American centers of plant origin, animals such as llama, alpaca, and turkey were domesticated.
Numerous zoological studies have confirmed that for each species of domestic animal, despite the abundance of breeds, there is, as a rule, one wild ancestor.
Thus, for most species of domestic animals and cultivated plants, despite their enormous diversity, it is usually possible to indicate the original wild ancestor.
II. Consolidation of knowledge
General conversation during the study of new material and filling out the table “Centers of origin of cultivated plants”
Table 1. Centers of origin of cultivated plants (according to N.I. Vavilov) |
Geographical position |
|
Cultivated plants |
South Asian tropical |
Tropical India, Indochina, Southern China, islands of Southeast Asia |
Rice, sugarcane, cucumber, eggplant, black pepper, banana, sugar palm, sago palm, breadfruit, tea, lemon, orange, mango, jute, etc. (50% cultivated plants) |
East Asian |
Central and Eastern China, Japan, Korea, Taiwan |
Soybean, millet, buckwheat, plum, cherry, radish, mulberry, kaoliang, hemp, persimmon, Chinese apples, opium poppy, rhubarb, cinnamon, olive, etc. (20% of cultivated plants) |
South-West Asian |
Asia Minor, Central Asia, Iran, Afghanistan, South-West India |
Soft wheat, rye, flax, hemp, turnip, carrots, garlic, grapes, apricot, pear, peas, beans, melon, barley, oats, cherries, spinach, basil, walnuts, etc. (14% of cultivated plants) |
Mediterranean |
Cabbage, sugar beet, olive (olive), clover, single-flowered lentils, lupine, onion, mustard, rutabaga, asparagus, celery, dill, sorrel, caraway seeds, etc. (11% of cultivated plants) |
Abyssinian |
Ethiopian Highlands of Africa |
Durum wheat, barley, a coffee tree, grain sorghum, bananas, chickpeas, watermelon, castor beans, etc. |
Central American |
Southern Mexico |
Corn, long-staple cotton, cocoa, pumpkin, tobacco, beans, red peppers, sunflowers, sweet potatoes, etc. |
South American |
South America along the West Coast |
Potatoes, pineapple, cinchona, cassava, tomatoes, peanuts, coca bush, garden strawberries and etc. |
III. Homework
Study the textbook paragraph (subject and objectives of selection, centers of origin of cultivated plants and domestication of domestic animals).
Lesson 3–4. Artificial selection is the main reason for the diversity of breeds and varieties
Equipment: portrait of N.I. Vavilova; tables on general biology;
: portrait of N.I. Vavilova; tables on general biology;
biological objects illustrating the diversity of varieties of cultivated plants, breeds of domestic animals and forms of artificial selection;
map of the main geographical centers of origin of cultivated plants;
biological objects for laboratory work.
I. Test of knowledge
A. Oral knowledge test
1) the subject and objectives of selection;
№ 1. 2) the teachings of N.I. Vavilov about the centers of origin of cultivated plants;
№ 2. 3) animal domestication centers.
№ 3. B. Working with cards
№ 4. The center of origin of corn is Central America, where it was cultivated even before the arrival of Europeans. Is the center of origin of any cultivated plant related to the presence of ancient agricultural centers? Which American agricultural civilization introduced corn into cultivation?
№ 5. How can we prove that behavioral selection played a central role in the early stages of domestication?
№ 6. What is the connection between the protection of wild relatives of cultivated plants and domestic animals and the tasks of developing new varieties and breeds?
B. Independent work
Students receive a list with the names of cultivated plants, which they must distribute according to the centers of origin in accordance with the given option.
1st option South Asian tropical; |
2nd option East Asian; |
3rd option South-West Asian; |
Plant names: |
||
1) sunflower; |
17) hemp; |
33) peas; |
Answers: |
||
1st option South Asian tropical: |
2nd option East Asian: |
3rd option South-West Asian: |
II. Learning new material
1. Charles Darwin’s disclosure of the reasons for the diversity of varieties and breeds
People have long been obsessed with the dream of managing heredity. They sought to find means to change heredity.
Most often, people changed heredity without even knowing it. Charles Darwin showed that this began with unconscious selection, when owners first preserved the most valuable specimens of domestic animals and cultivated plants. People did not think about directed changes in breeds and varieties; nevertheless, animals and plants changed from generation to generation. Thus, the main reason for the diversity of breeds and varieties is artificial selection. Selection made by man on the basis of hereditary variability in order to create breeds and varieties is called.
While visiting agricultural exhibitions, Charles Darwin drew attention to the wide variety of breeds and varieties and set out to find out the reasons for this diversity. By the 40s.
XIX century a large number of breeds of cattle (dairy, meat, meat and dairy), horses (draft horses, racing horses), pigs, dogs, and chickens were known. The number of wheat varieties exceeded 300, grapes - 1 thousand. Breeds and varieties belonging to the same species were often so different from each other that they could be mistaken for different species.
Many supporters of the doctrine of constancy and immutability of species believed that each breed, each variety descended from a separate wild ancestor. Darwin studied in detail the origin of different breeds of domestic animals and came to the conclusion that man himself created all their diversity, as well as the diversity of varieties of cultivated plants, changing in different directions one or several ancestral wild species. Darwin studied in particular detail the origin of domestic pigeon breeds. Despite the great differences, breeds of domestic pigeons have very important common characteristics. All domestic pigeons are social birds, nesting on buildings, and not in trees, like wild ones. Pigeons of different breeds easily interbreed and produce fertile offspring. When crossing individuals belonging to different breeds
, Darwin received offspring that were surprisingly similar in color to the wild rock (rock) pigeon. The scientist concluded that all breeds of domestic pigeons originated from one species - the wild rocky pigeon, which lives on the steep cliffs of the Mediterranean coast and further north, to England and Norway. The common rock pigeon is similar to it in plumage color.
Through an accurate study of anatomical and physiological characteristics, Charles Darwin established that all breeds of domestic chickens originated from the banker chicken, a wild species living in India, Madagascar and the Sunda Islands; breeds of cattle - from the wild aurochs, exterminated in the 17th century; pig breeds - from wild boar. Varieties of garden cabbage originated from wild cabbage, which is still found on the western shores of Europe.
Darwin turned to agricultural literature, exhibition reports, old catalogs and price lists, studied the practices of horse breeders, pigeon breeders, and gardeners and found that new breeds and varieties were constantly appearing, which were more advanced and diverse in their characteristics compared to previously existing ones.
In some cases, new signs in domestic animals and cultivated plants arose accidentally, suddenly; man did not accumulate them through directed selection. This is how short-legged sheep and whole-leaf strawberries appeared. They interested a person with their unusualness, and he consolidated these characteristics into a breed or variety. But, as a rule, a person actively participated in the long process of creating the characteristics and properties of breeds and varieties he needed.
In a herd, flock, in a field, in a garden bed, etc.
a person noticed an individual animal or plant with some kind of hereditary difference of interest to him, even a minor one, selected these individuals for a tribe and crossed them. All other individuals were not allowed to reproduce. From generation to generation, individuals in which this hereditary trait was most noticeably expressed were retained as producers. Thus, the trait was enhanced and accumulated in this artificial population.
Selection was sometimes preceded by crossing to obtain combinations of genes in the offspring, and therefore more diverse material, for artificial selection. For example, the ancestor of the world famous Russian breed of Oryol trotters was obtained this way. First, a stallion of the Arabian riding breed was crossed with a Danish draft horse, and the stallion that emerged from them was crossed with a horse of the Dutch trotting breed. Then selection was carried out according to certain characteristics.
2. Forms of artificial selection carried out according to external, phenotypic characteristics in populations of plants and animals. For example, in front of us is an alfalfa field with 1 thousand plants growing. Having carefully examined each plant during its growth, taking into account their productivity in terms of seeds and green mass during harvesting, we selected the 50 best in all respects. By combining the seeds of these selected 50 plants, next year we are planting a new field, on which we expect to obtain a population of alfalfa, this wonderful high-protein forage plant, that is improved in productivity and other characteristics.
If we have achieved improvement, then we can assume that mass selection for external characteristics was effective. However, this form of selection has significant drawbacks, because We cannot always determine the best genotype based on external characteristics. Mass selection is the most ancient form of selection.
Mass selection can be effective when individuals are distinguished according to qualitative, simply inherited, traits (white or Red flower, horned or hornless animal, etc.). It is usually used for cross-pollinated plants. For example, new varieties of rye were obtained, in particular the Vyatka variety.
At individual selection select an individual with a trait of interest to a person and obtain offspring from her. The introduction of individual selection was a truly revolutionary stage in the development of breeding. This happened in the middle of the 19th century, when the famous French breeder J. Vilmorin outlined the basic principles of this form of selection, the main one of which was the evaluation of selected plants or animals by their offspring. Most often, this form of selection is used in relation to self-pollinating plants, when only one individual of wheat, oats, or barley participates in reproduction. The offspring of one self-pollinating individual is called clean line, which consists of homozygous forms.
Let's return to the same example with the alfalfa field. Having selected from 1 thousand the 50 plants that are best in terms of external characteristics, in the case of individual selection, we will not combine their seeds, but next year we will sow the seeds of each of the 50 plants separately and thereby evaluate all the offspring of each of the selected plants according to all characteristics. In this way, the genotype of the selected plant is assessed, and not just its phenotypic characteristics. If each plant or animal selected from a population for outstanding characteristics retains its characteristics in the offspring, individual selection continues in subsequent generations.
The advantage of individual selection over mass selection lies in the accuracy of genotype assessment when analyzing individual descendants.
When selecting individuals for quantitative traits that are usually very difficult to inherit (the number of grains in an ear of wheat, the fat content of a cow's milk, etc.), where an extremely accurate assessment of the genotype is needed, individual selection is most effective.
3. The creative role of artificial selection
Selection leads to a change in an organ or trait, the improvement of which is desirable for a person. Breeds and varieties descended from common wild ancestors developed under the influence of man in different directions in accordance with his economic goals, tastes and needs. They became more and more unlike each other and the wild species from which they came. It would be wrong to compare the role of artificial selection in the evolution of breeds and varieties with a sieve through which deviations unsuitable for humans are simply eliminated. The selection of individuals with hereditary changes necessary for humans leads to the creation of completely new varieties and breeds, i.e.
never before existing organic forms with characteristics and properties formed by man himself. This is the creative role of artificial selection.
Artificial selection is the main driving force in the formation of new breeds of animals and plant varieties adapted to human interests. The doctrine of artificial selection theoretically generalized thousands of years of human practice in creating breeds of domestic animals and varieties of cultivated plants and became one of the foundations of modern selection.
III. Consolidation of knowledge
Performing laboratory work. Laboratory work: “Studying the results of artificial selection” Equipment: various varieties
indoor plants
1. Compare the plants of the two varieties offered to you for work. Determine in what ways they differ from each other to a greater extent.
2. What is the significance of the diversity of traits in the plant varieties you are considering for humans?
3. Make a guess as to what factors influenced the changes in the plant organs of the varieties you are considering.
What is the role of man in this?
4. Explain how you understand the expression “the creative role of artificial selection.”
5. Conclusion: about the main reasons for the variety of varieties of indoor plants that you considered during laboratory work.
IV. Homework
Study the textbook paragraph (C. Darwin on the reasons for the diversity of breeds of domestic animals and varieties of cultivated plants, artificial selection and its forms, the creative role of artificial selection).
Fill out the table “Comparison of artificial and natural selection.”
To be continued
The success of breeding work largely depends on the quality of the source material, mainly on its genetic diversity. The more diverse the source material for selection, the more opportunities it provides for hybridization and selection. Breeders, taking advantage of the biological, genetic and environmental diversity of the plant world, have created a huge number of different varieties of cultivated plants. Modern cultivated plants are grown simultaneously in different countries, on different continents. However, each of these plants has its own historical homeland - center of origin
. It was there that the wild ancestors of the cultivated plant were or are still located, where its genotype and phenotype were formed. Doctrine of centers of origin of cultivated plants
created by the outstanding Russian scientist N.I. Vavilov.
| N.I. Vavilov initially identified 8 centers of origin of cultivated plants with a number of subcenters, but in later works he consolidated them into 7 main primary centers (see Table 4 and Fig. 42). Name of the center and number of occurrences here cultural species | (% of 1000 - total number studied) |
| Cultivated plants that arose in this center from ancient cultures | 1. South Asian tropical (about 50%) |
| Sugarcane, cucumber, eggplant, citrus, mulberry, mango, banana, coconut, black pepper | 2. East Asian (20%) |
| Soybean, millet, oats, buckwheat, chumiza, radish, peach, tea, actinidia | Wheat, rye, peas, lentils, flax, hemp, melon, apple, pear, plum, apricot, cherry, grapes, almonds, pomegranate, figs, onions, garlic, carrots, turnips, beets |
| 4. Mediterranean (11%) | Wheat, oats, rye, cabbage, sugar beets, dill, parsley, olive, bay, raspberry, oak, cork, clover, vetch |
| 5. Abyssinian | Sorghum, durum wheat, rye, barley, sesame, cotton, castor, coffee, date palm, oil palm |
| 6. Central American | Corn, beans, potatoes, pumpkin, sweet potatoes, peppers, cotton, tobacco, shag, sisal (fibrous agave), avocado, cocoa, nuts, pecans |
| 7. Andean (South American) | Potatoes, corn, barley, amaranth, peanuts, tomato, pumpkin, pineapple, papaya, cassava, hevea, cinchona, feijoa, coca, Brazil nut (bertholletia) |
Rice. 42. The main geographical centers of origin of cultivated plants: I - South Asian tropical; II - East Asian; III - South-West Asian; IV - Mediterranean; V - Abyssinian; VI - Central American; VII - Andean (South American)
Most of the centers coincide with ancient centers of agriculture, and these are predominantly mountainous rather than flat areas. The scientist highlighted primary And secondary centers of origin of cultivated plants. Primary centers are the homelands of cultivated plants and their wild ancestors. Secondary centers are areas where new forms emerge not from wild ancestors, but from previous cultural forms, concentrated in one geographical location, often far from the primary center.
Not all cultivated plants are cultivated in their places of origin. Migration of peoples, navigation, trade, economic and natural factors have at all times contributed to the numerous movement of plants to other areas of the Earth.
In other habitats, plants changed and gave rise to new forms of cultivated plants. Their diversity is explained by mutations and recombinations that appear in connection with the growth of plants in new conditions.
A study of the origin of cultivated plants led N.I. Vavilov came to the conclusion that the centers of formation of the most important plant crops are largely connected with the centers of human culture and with the centers of diversity of domestic animals. Numerous zoological studies have confirmed this conclusion.
The study of the origin and evolution of cultivated plants is considered one of the essential branches of selection. N.I. Vavilov wrote that all breeding work, starting from the source material, establishing the main areas of origin of species and ending with the creation of new varieties, is, in essence, a new stage in the evolution of plants, and selection itself can be considered as evolution directed by the will of man.
