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0GEOGRAPHIC DISTRIBUTION OF PLANTS IN THE SELECTION OF AGRICULTURAL CROPS BY N.I. VAVILOV
Mukhammadqulova M.A.
Samarkand State University named after Sh. Rashidov, Institute of Agrobiotechnology and Food Security, Department of Horticulture and Viticulture, specializing in the selection and seed production of agricultural crops, 206th group student. https://doi.org/10.5281/zenodo.14030947
Abstract. The laws of the Republic of Uzbekistan "On Selection Achievements" and the new edition of "On Seed Production" dated February 16, 2019, the resolution of the President of the Republic of Uzbekistan dated December 29, 2015, PR-2460 "Measures for Further Reforming and Developing Agriculture in 2016-2020", the decree of the President of the Republic of Uzbekistan dated February 7, 2017, PD-4947 "On the Strategy of Actions for Further Development of the Republic of Uzbekistan," as well as other regulatory legal documents related to this activity, emphasize the great importance of selection and seed production in achieving high-quality yields from agricultural crops today. Numerous experiments are being conducted by scientists to create new varieties and primary sources. The main directions of selection work in Uzbekistan, the use of traditional methods (cross-cultivation, long-formed cross-cultivation, polyploidy, mutagenesis, heterosis) alongside biotechnology, genetic engineering, and other new methods, the significance of the variety in agriculture, and selection methods have been studied in this article.
Keywords: rice, white corn, dagussa, chickpeas, pigeon pea, mung bean, sesame, safflower, woody cotton, kenaf black pepper, eggplant, cucumber, Indian salad, lemon, orange, grape, pear, cherry, pomegranate, quince, walnut, almond, and fig.
Introduction. The development of the horticulture sector in the Republic of Uzbekistan, particularly fruit growing, necessitates the involvement of qualified specialists in the field to introduce new technologies and transition to market relations, as well as to support the rapid development of farmer households. One of the most important areas for the intensive development of horticulture is the cultivation of seedlings. The use of high-quality seedling products in the establishment of fruit orchards is a guarantee of high yields.
To achieve such results, it is crucial for specialists to be well-informed about the technology of propagating fruit seedlings. N.I. Vavilov revealed a number of regularities regarding the geographic distribution of plants and clarified the directions for searching for new species and varieties. Vavilov created a theory on the center of origin of cultivated plants by studying the plant world of over 60 countries. According to him, the current diversity is not evenly distributed across the earth. In some regions, diversity is very pronounced, including Southeast China, the IndoChina region, India, the Malay Archipelago, Southeast Asia, Tropical Africa, Ethiopia, Central and South America, the countries around the Mediterranean Sea, the Middle East, and other regions.
In contrast, Northern countries, Siberia, Central and Northern Europe, and America are characterized by a scarcity of plant diversity. From this, it follows that the origin of certain plant species occurs in specific geographic locations. The geographic study of plants has helped to identify distinct cultural floras.
To achieve this, the botanical-geographic differentiation method developed by N.I. Vavilov has been very useful. According to Vavilov, the area where cultivated plants are concentrated can simultaneously serve as the center of origin for these plants. Regions with maximal diversity of cultivated plant species and their varieties have been identified. The sources of cultivated plants are separated by mountain ranges, deserts, or water borders, creating agricultural civilizations that are isolated from one another. The total area of such centers constitutes 2.5% of the landmass. In many cases, a single generation or species is associated with one center, but some crops are linked to the diversity of two or more centers.
For this reason, N.I. Vavilov primarily distinguished the initial center of plant formation. This area stands out for its richness in diversity and the fact that the plants were domesticated there. The second center of plant diversity consists of distinct forms that have migrated from the first center. For example, the primary center for maize is Mexico, while China is considered the second center for waxy types. Barley exhibits its diversity in East Asia (the first center) as well as in Central and the Middle East, and it is also found in East Africa.
Most cultivated plants have not left their primary centers of origin. Dozens, and even hundreds, of cultivated plant species still remain in their original domestication regions. However, for some cultivated plants, there is currently an inconsistency in the diversity of the plants in their centers of origin across different regions. This inconsistency arises when forms developed from the initial material are cultivated in another region, leading to that area being accepted as their center of origin. Such a situation applies to soft wheat, whose diversity may have originated from Central Asia, while its true origin is considered the Near East. This is because only in the Near East can the initial material types be found, and their hybridization has led to forms that appear in Central Asia.
As shown by N.I. Vavilov in many examples, the highest levels of variability and concentration of dominant genes are found in the center of formation of a crop, and this index decreases at the edges of the center. This is due to the emergence of recessive traits as a result of selection and other influencing factors. According to him, true types of plants are more likely to be found farther from the center.
N.I. Vavilov identified eight distinct centers of origin for cultivated plants:
The Chinese Center includes the mountainous regions of Central and Western China. From here, 136 cultivated plants have spread. This center is considered the origin for 21 varieties of flax (three types), mung beans, soybeans, and several other grains and legumes.
The Indian Center is the second main center and includes the Indian subcontinent, Myanmar, and the Assam state of India. From this center, 117 cultivated plants have originated, including rice, white maize, taro, chickpeas, pigeon peas, mung beans, sesame, safflower, wood fiber cotton, kenaf, black pepper, and others. Additionally, eggplants, cucumbers, Indian salad, lemons, oranges, and some varieties of mandarins are also considered native to this region.
The Indo-Malay Center supplements the Indian center and encompasses the Malay Archipelago, the Philippines, and Indochina. In this region, N.I. Vavilov identifies 55 cultivated plants. From here, bananas and some citrus plants, as well as coconut palms, have originated.
The Central Asia Center. This center encompasses Northern and Western India (Punjab), the northern part of Pakistan, Afghanistan, Tajikistan, Uzbekistan, and Western Tien Shan. This area is considered the center for 42 cultivated plants. From this region, the hexaploid type of soft
wheat, durum and round wheat, peas, lentils, horse beans, chickpeas, and 26-chromosome varieties of fiber cotton have originated.
The Near East Center. This center includes the Near East, that is, Asia Minor, the Caucasus, Iran, and the mountainous regions of Turkmenistan. This area is home to 84 types of cultivated plants. This region is distinguished by the abundance of cultivated wheat varieties, which are considered the main center of origin for these varieties. Additionally, grapevines, pears, plums, pomegranates, quince, walnuts, almonds, and figs originated here. Varieties of melons and edible herbs such as alfalfa, asparagus, and vetch have also spread from this region.
The Mediterranean Center. From here, a total of 84 cultivated plant species have spread. This area is known for the distribution of vegetable crops, including radishes, cabbages, salads, and others. It is the second center for crops such as hemp, barley, horse beans, and chickpeas.
The Abyssinian Center is an autonomous center for world cultivated plants, from which 38 species have spread (Africa). Despite the small area of cultivated land, this region is notable for the high number of varieties. For example, in terms of the botanical diversity of wheat, this center ranks first. It also ranks high in the variety of barley types. From this region, coffee trees, date palms, maize, African flax, sesame, and Abyssinian bananas have originated.
The Southern Mexico and Central America Center. From this center, 49 species of cultivated plants have originated. Such plants include maize, major types of American beans, medium varieties of squash, peppers, and many tropical fruits. Avocados, cocoa, sweet potatoes, and American cotton have been domesticated here. The varieties derived from American cotton are currently the basis for global cotton production.
The South American Center (Peru-Ecuador-Bolivia). Geographically, this includes the mountainous and foothill regions of Colombia, Ecuador, Peru, and Bolivia. From the Brazil-Paraguay center, 13 cultivated species have emerged, including manioc, peanuts, some cocoa varieties, and pineapples.
The centers identified by N.I. Vavilov are located in tropical and subtropical regions, in mountainous or hilly areas. It is challenging to explain the diversity of plant life in these places, as the conditions for cultivated plants are not particularly favorable. Moreover, in these centers, natural hybrids occur, and new traits and characteristics may emerge. The conditions for the emergence of new forms in the above genetic centers could change slightly, providing favorable conditions for plants. In the selection and breeding of grain crops, the initial material includes nearly 40,000 samples of wheat from the world collection of the Vavilov Institute of Plant Industry (VIR).
Breeders have created high-yielding varieties that can be successfully used in breeding aimed at this extremely important trait. For example, numerous varieties have been developed worldwide using the well-known winter wheat varieties Bezostaya 1 and Mironovskaya 808. Their forms are considered valuable initial material. In wheat breeding, the varieties from the International Center for Wheat and Maize Improvement in Mexico, as well as those from Germany, Sweden, Russia, Ukraine, China, India, and other countries, are widely used.
Winter-hardy varieties of wheat have been developed in Russia. Among the frost-resistant varieties, those from the Volga region (for example, Albidum 114) and the winter wheat varieties from the steppe region of Ukraine stand out. The Mironovskaya 808 variety is also notable for its winter hardiness due to its strong tillering ability.
For creating drought-resistant varieties, there is a rich source of initial material available from the Volga region, southern Ukraine, southeastern Kazakhstan, and western Siberia. For instance, the well-known spring wheat variety Saratovskaya 29 stands out for its exceptional drought resistance.
Drought-resistant varieties also exist in Mexico, Australia, the USA, Canada, and other countries. There is a good correlation between winter hardiness and drought resistance, although they may not always match intensively. The ability to withstand lodging is generally associated with low stature and is a characteristic found in many varieties. However, there are also tall lodging-resistant varieties, such as the Leningrad variety of spring wheat. Varieties that are very resistant to shattering, with a rigid spike (which retains the grain securely), are also important. I have studied how the ancient varieties of semi-tame populations, from which these forms were created, hold significant importance.
I have devised plans for future scientific research aimed at creating primary sources for the selection of agricultural crops to obtain high-quality yields. Additionally, in-depth studies of plant genetic resources and gene banks will assist in ensuring that newly developed varieties serve agriculture for many years to come. The cultivated crops from each of the centers established by N.I. Vavilov are traditional crops that have adapted to local conditions. They possess unique characteristics and are used as the basis in the selection process.
In creating quality varieties, gene banks serve as a database for storing genetic material of crops, which includes traits such as resistance to various environmental conditions and high yield.
REFERENCES
1. The Law of the Republic of Uzbekistan on "Achievements in Selection" and the new edition of the "Law on Seed Production" dated February 16, 2019.
2. The Resolution of the President of the Republic of Uzbekistan dated December 29, 2015, No. PQ-2460 on "Measures for Further Reform and Development of Agriculture in 2016-2020."
3. Abdukarimov D.T. Selection and Seed Production of Grain Crops. Tashkent, 2010.
4. Abdukarimov D.T. Private Selection and Seed Production of Field Crops. Tashkent, 2007.
5. Abdukarimov D.T., Ergashev I.T., Bekmuradova X.K. General Selection and Seed Production. Textbook. Tashkent, 2021.
