Selection of kolrabi cabbage varieties and samples for the central zone of Uzbekistan

. In the Republic of Uzbekistan, experts in the field of vegetable cultivation are faced with the task of satisfying the population's need for vegetable products by not only growing their variety and number but also enhancing their quality. The fact that over 80% of the farmed space was occupied by just ten crops, however, highlights the lack of variety in vegetable production. This is mostly because early-ripening, high-yielding, and vitamin-rich vegetable types appropriate for local circumstances have not been sufficiently developed, and there is a need for more study into gardening methods. For three years 13 varieties and samples of kohlrabi cabbage collection were studied according to morphobiological and economic characteristics. In the course of research, 4 varieties were selected for early ripening, including VIR k-41 (France), Pikant, Nezhenka and Smak (Russia), 4 Giants for productivity, Delikatesnaya belaya, Smak and Violetta varieties were selected, and 4 samples of VIR K-41, Pikant, Smak and Fioletovaya varieties were selected according to their complex characteristics (earliness, productivity and marketability). In the future, these selected varieties and samples will serve as a primary source for the creation of early-early, fruitful, environmental stress-resistant varieties suitable for the climatic conditions of Uzbekistan.


Introduction
Specialists in the field of vegetable production in the Republic of Uzbekistan face the challenge of meeting the population's demand for vegetable products by not only increasing their quantity but also improving their quality and variety [1][2][3][4]. Currently, only about 40 types of vegetable crops are grown in Uzbekistan, while 1,200 types have been identified globally, with 600 of them being cultivated. In 2021, 315.42 thousand hectares of land were used to grow 45 types of vegetables, with potatoes, tomatoes, carrots, onions, cucumbers, cabbage, garlic, melons, watermelons, and pumpkins being the most commonly grown [5][6][7]8]. However, only 10 crops accounted for almost 80% of the cultivated area, indicating a lack of diversity in vegetable production. This is mainly due to the insufficient development of early-ripening, high-yielding, and vitamin-rich varieties of vegetables suitable for local conditions and the need for further research into cultivation techniques [9].
In Uzbekistan, there is a strong emphasis on promoting healthy eating habits. To support this, the Cabinet of Ministers of the Republic of Uzbekistan issued a decision on November 10, 2020 (No. PQ-4887) that aims to provide the population with a diverse selection of agricultural and vegetable products to promote a balanced and nutritious diet [10][11][12]. This research work is seen as contributing to the achievement of this goal to some extent.
Vegetables are a crucial source of vitamins and contain over 50 different chemical elements, with an ash content of 0.1-2%. They also contain important salts such as sodium, potassium, calcium, phosphorus, magnesium, iron, manganese, chlorine, iodine, and sulfur, which help to neutralize acidic compounds produced during the digestion of bread, oil, and meat [5][6][7]9]. This helps to maintain a constant alkalinity level in the blood. Vegetables also contain organic acids, enzymes, essential oils, and aromatic substances that stimulate appetite and improve the absorption of proteins, carbohydrates, and fats, particularly in apples, lemons, wine, and shallots. In addition, vegetables provide indigestible waste products that are essential for healthy digestion. The therapeutic properties of vegetables have been recognized since ancient times, with their ability to regulate nervous excitement and prevent nervous and mental conditions [3][4][5]11].
Kohlrabi cabbage is a new vegetable in Uzbekistan and is used by different groups of people to make salads and dishes because of its high vitamin content. Since 2018, its cultivation areas have been expanding due to its export potential. The main reason for growing kohlrabi cabbage is its medicinal properties and quick preparation. It contains various vitamins and minerals that are essential for the human body and can help clean the body from toxins and improve cellular activity. Additionally, kohlrabi is rich in carbohydrates, proteins, and biologically active substances [1][2][3][4][5]7]. Although kohlrabi cabbage shares biological characteristics with other types of cabbage, it differs from them in terms of its physical structure. It has the advantage of quick ripening, high vitamin retention, ability to withstand soil salinity, and low requirement for soil fertility. This research aims to investigate the suitability of different varieties and samples of kohlrabi cabbage for the central zone of Uzbekistan.

Method and materials
Research was conducted to study the economically valuable characteristics of kohlrabi collection samples. The study was conducted using the methodical manual of the All-Russian Research Institute of Plant Science (VIR) (Fig. 1) on "Research and restoration of the world collection of cruciferous plants" [4] and the method proposed by B.A. Dospekhov [5]. The research involved the study of various varieties of kohlrabi cabbage, which were introduced from Russia, including Venskaya belaya 1350, VIR K-214, VIR K-206, VIR K-41, Fioletovaya, Gigant, Sirenovy tuman, Pikant, Delikatesnaya belaya, Violetta, Smak, and Nezhenka. Additionally, the Amokashi variety, which is commonly grown in the researcher's republic, was also included as a sample.
The research was conducted at the "Educational-Consultative Center" of the Tashkent State Agrarian University, situated in the Qibrai district of the Tashkent region. The experiments were carried out in cultivated fields during the growing season. The Agrochemical Analysis Center of the Tashkent region provided information regarding the soil composition of the experimental fields. According to this information, the arable layer (0-30 cm) of the soil contained 1.6-1.87% humus, 0.135% nitrogen, 0.37% phosphorus, and 10% potassium [4][5][6]8]. The Tashkent region is located in the north-eastern part of Uzbekistan, sharing borders with Kazakhstan to the north-west, Kyrgyzstan to the north-east, Namangan region to the east, Tajikistan to the south, and Syrdarya regions to the south-west. The region has a continental climate with mild and wet winters and hot and dry summers [1][2][3]. The area experiences strong sunlight with 2800-2900 hours of sunshine per year, 360-400 hours in the summer months, and 90-100 hours in the winter months. Cloudy days are infrequent, with only 10 to 25 days of clouds observed in December and January. The average annual air temperature at the "Aq Zukuk" weather station in the Qibray district is 14-17 0 C between March and May, and 28.2-32.4 °C between June and September. From September onwards, the temperature drops to 18.4 °C [1][2]. The Qibray district is located in an arid region that receives a total of 250-500 mm of rainfall per year, mainly during the winterspring months. March is the month with the highest precipitation. Snow can be seen in the area for 25-35 days.

Results and discussion
From 2015 to 2017, experiments were conducted on typical gray soils in the experimental fields of the Tashkent State Agrarian University Information and Consulting Center (EXTENSION CENTER) DUK. Kohlrabi cabbage seedlings that were 30 days old were planted in the open field on March 10, in a 70x30 plot. Each experimental unit was 4.2 m 2 , and 20 plants were planted. The Amokashi variety, which is zoned for the region, was chosen as the model and studied. Morpho-biological and economic characteristics of 10 plants from each variety were studied during the growth period. This included the number of leaves on the plant, the level of the leaf plate, the length of the leaf band, the shape and color of the fruit, the formation of 10% and 70% of fruits, the ripening of the crop at 10% and 75% of the harvest, the average weight of one fruit (g), productivity, and the share of marketable products.
Observations were made 30 days after planting kohlrabi seedlings in the experimental field, and it was found that stem formation began first in the Russian Nejenka variety, followed by Smak, Picant, Venskaya Belaya 1350, and the French K-41 sample on the 30th day. In German K-206, Czech Violetta, Japanese K-214, Russian Delikatesnaya Belaya, Sirenovy Tuman, and Fioletovaya varieties, this process was observed 35 days after planting, while in the Czech Giant variety, it was observed on the 42nd day after planting.
The process of fruit formation in different kohlrabi varieties varied in duration. French k-41 and Russian Nejenka varieties took 5 days to form 75% of the fruit, while Russian Delikatesnaya Belaya took 7 days, and German k-206, Czech Violetta, and Russian Sirenovy Tuman took 8 days. Czech Giant, Russian Venskaya Belaya 1350, and Fioletovaya varieties lasted for 9 days, while it took 11 days for the Russian Smak variety and 14 days for the Japanese k-214 sample. The standard Amokashi variety took 10 days for this process.
The Amokashi variety took 60 days to ripen 10% of the crop and 75 days to ripen 75% of the crop after planting. Among the different varieties and samples studied, the Russian Nejenka variety and French VIR k-41 sample were the earliest to ripen, with 10% of the fruits ripening on the 57-60th day and 75% ripening on the 66th day after planting. In the German VIR k-206 sample, the ripening of 10% of the pods was observed on the 70th day after planting, and 75% of the pods ripened on the 76th day after planting. The Russian varieties Pikant and Venskaya Belaya 1350 took 72-78 days to ripen the pods ( Clearly, there are different ripening patterns of several cultivars of beans, including Delikatesnaya Belaya, Sirenovy District, Smak, Violetta, and Russian Fioletovaya. It was found that 10% of the bean pods ripened on the 76th day after planting for some of these cultivars, while others took longer, with 75% of the pods ripening between 85-100 days after planting. Specifically, the Russian Fioletovaya variety took 89 days to reach 10% ripeness. The text describes the growth periods of different samples of plants in Uzbekistan. The growth period was determined based on the day when 50% of the plants in the experimental section ripened. The study found that the growing period in Uzbekistan's climate was between 62-95 days for different samples. VIR K-41 (Red crown), Pikant, Smak, and Nezhenka had the shortest growing period of 62-65 days, while Gigant, Sirenovy tuman, and Fioletovaya varieties had the longest growing period of 90-95 days. The Amokashi variety was identified as an early variety with a growing period of 62 days. Other varieties had growing periods ranging from 70-85 days.
The passage details the results of a comprehensive three-year study on kohlrabi cabbage collection samples. Among the diverse range of samples studied, four varieties were selected based on their ability to ripen early, including VIR K-41 (France), Picant, Nezhenka, and Smak (Russia). These chosen varieties exhibited a relatively short growing period of 62-65 days and displayed higher productivity levels, ranging from 3.18-10.25 tons per hectare, in comparison to the model variety (Fig.2). Furthermore, the research found that the plants exhibited 100% viability, potentially due to the seedlings being cultivated from the collection samples. Additionally, the study concluded that the samples with the largest fruits in proportional condition yielded the highest productivity, indicating a correlation between fruit size and productivity.
It was found that among the samples, Giant had the heaviest fruits, with an average weight of 818.2 grams, followed by Delikatesnaya Belaya and Smak with an average weight of 608.1 grams, and Fioletovaya with an average weight of 588.5 grams. Sirenovy Tuman and Violetta also had relatively large fruits with an average weight of 584.3 grams and 590.1 grams, respectively. These varieties had fruits that were significantly larger than the standard variety, with a difference of 160.6-394.5 grams. On the other hand, Amokashi had the smallest fruits with an average weight of 423.7 grams. The weights of other kohlrabi varieties were also provided in the text ( Table 2). According to the results, among the collection of kohlrabi varieties and samples, Giant (818.2 g), Delikatesnaya Belaya and Smak (608.1 g), Fioletovaya (588.5 g), Sirenovy Tuman (584.3 g), and Violetta (590.1 g) exhibited the largest fruit sizes. These varieties were found to have a substantial weight difference of 160.6-394.5 grams compared to the standard variety, as illustrated in Fig. 3.   Fig. 3. Samples of varieties selected from the kohlrabi collection according to yield.
The text describes the methodology used to assess the marketability of various varieties and samples of kohlrabi cabbage in a research project. The evaluation process involved calculating the proportion of marketable produce, which was defined as unripe, mediumsized cabbage heads, out of the total yield. The results were then presented in a table, detailing the performance of each variety and sample in terms of marketability. According to the data, a harvest of 2,356 kg was obtained from an area of 1 square meter planted with the Amokashi variety. Out of this, 2,196 kg of the harvest was deemed to be marketable. The marketable produce accounted for 88% of the total harvest, while the remaining 12% consisted of cracked and small fruits (Table 3). The text reports on the findings of a research study that aimed to examine the correlation between yield and marketability in various kohlrabi cabbage varieties and samples. The investigation revealed that the marketability of the crop was affected by air humidity, and that high-yield varieties were not necessarily high in marketability. Specifically, the VIR K-214, Gigant, and Delikatesnaya belaya varieties and samples demonstrated the lowest marketability results. Conversely, the samples of VIR K-41, Fioletovaya, Venskaya belaya 1350, Pikant, and Violetta varieties showed the highest marketability results, with an indicator 1-4% higher than that of the Amokashi variety. Moreover, the study showed that the Smak and Sirenovy district's Smak and VIR K-206 variety samples accounted for 89% and 86% of the total gross product, respectively (Fig.  4). The kohlrabi cabbage collection is a valuable resource comprising varieties and samples with diverse characteristics. Among these, four varieties, VIR K-41, Pikant, Smak, and Fioletovaya, were selected based on their complex characteristics ( Table 4). The yield performance of these selected varieties was assessed by measuring the harvest per square meter (kg/m 2 ). Results showed that VIR K-41 had a higher yield of 0.410 kg/m 2 compared to the Amokashi variety. The spicy variety had a yield of 0.358 kg/m 2 , while the Smak and Fioletovaya varieties had yields of 0.832 kg/m 2 and 0.804 kg/m 2 , respectively.

Conclusions
After conducting a comprehensive three-year study on various kohlrabi cabbage collection samples, four varieties, namely VIR k-41 (France), Pikant, Nejenka, and Smak (Russia), were identified as having early ripening characteristics. These selected varieties require a growing period of 62-65 days and were found to be more productive than the standard variety, with yields ranging from 3.18-10.25 tons per hectare. Several kohlrabi varieties and samples were chosen from the collection based on their productivity, including Gigant, Delikatesnaya belaya, Smak, Fioletovaya, Sirenovy tuman, and Violetta. The results of the study showed that the marketable productivity of these selected samples is 10-80% higher than that of the average Amokashi variety.
It was found that the kohlrabi cabbage varieties VIR K-41, Fioletovaya, and Smak can serve as primary resources for developing early and high-yielding varieties in the climatic conditions of the researchers' republic. The study showed that red and black-fruited kohlrabi varieties are relatively resistant to cracking and diseases in the same climatic conditions. Using kohlrabi varieties in vegetable production is essential for utilizing available land resources effectively and increasing vegetable diversity.