Cultivation and Management of Watermelon

The seedless watermelons grown on the production now are triploid (3X) watermelons. It is a generation hybrid produced by tetraploid (4X) watermelon as female parent and diploid (2X) watermelon as male parent. The seedless watermelons currently cultivated are not completely seedless, and there are undeveloped small, white seed coats like the tender cucumber seeds, which have a seed-free feel and are called seedless watermelons. (I) Characteristics of cultivation and management The chromosomes of seedless watermelon cells are different from those of diploid ordinary watermelons, and therefore have characteristics and characteristics different from that of diploid ordinary watermelons. The measures for cultivation and management are the same as for diploid ordinary watermelon, and some measures are different. Therefore, cultivation and management must be carried out according to the characteristics of the seedless watermelon. 1. Seeds "shell" Seedless watermelon seeds have thick seed coats, especially thicker umbilical parts, and the seed embryos (ie, seed kernels) are not full, so sprouting is very difficult and must be "broken" in order to successfully germinate. After the seeds are sterilized, they are soaked for 8 to 10 hours. Remove the surface water and mucilage from the seeds with a dry cloth, and gently brush the umbilicals with the teeth. When the seedlings are planted, the seedlings will be erected vertically, and the seedlings will be opened so that they will open a small mouth, occupying about 1/3 of the length of the umbilicus. When pods are used, they must be light, and the seed coat must be small, so don't injure the kernels. You can also use the wire clamp to gently clamp the seed nozzle open, or use a knife to cut the umbilical on both sides, and perform the "broken shell." 2. The germination and seedling raising temperature is higher The seedless watermelon germination requires a higher temperature, which is about 3~5°C higher than that of the diploid ordinary watermelon, ie, 32~35°C is appropriate. Seedling temperature is also higher than ordinary watermelon 3 ~ 4 °C, therefore, in addition to the use of nursery seedlings, to strengthen the seedbed insulation work, such as the erection of wind barriers, thick straw or wheat straw and so on. In addition, in the management of seedbeds, the amount of ventilation should also be appropriately reduced to prevent the temperature inside the bed from falling too quickly. 3. Early seedling Seedless watermelon seedling growth is slow, growth is weak, early seeding should be sown earlier than ordinary watermelon. As seedless watermelons are more heat-resistant than ordinary watermelons, seedlings are often used in nurseries, such as electric hotbeds, hot pots, and heated greenhouses. Seeding period should be 3 to 5 days earlier than ordinary watermelon. 4. After the fertilizer and water seedling attacked the seedless watermelon, the roots were well developed and the stems and leaves grew vigorously. Therefore, the amount of fertilizer required was more than that of diploid ordinary watermelon. General Mushi soil miscellaneous fertilizer 4000 to 5000 kilograms, cake fat 60 to 80 kilograms, superphosphate 40 to 50 kilograms, ammonium sulfate 50 kilograms or urea 30 kilograms, potassium sulfate 25 kilograms. Soil manure and phosphate fertilizer for the base fertilizer ditch application or acupuncture, other fertilizers to do dressing 3 to 4 times. Seedless watermelon grows slowly at seedling stage, and grows faster after reaching vines. It is even more prosperous at flowering and fruit setting. If fertilizer and water supply is improper, it is easy to cause runners to run and it is difficult to establish fruit. Therefore, fertilizer and water should be properly controlled before the flowering of the female flower from the seedling "flipping tap" to the target node. It is advisable to water with a small amount of water. After 5 to 7 days of fruit setting, after the size of young fruit eggs, increase the amount of fertilizer and water supply, and make the fruit grow quickly. 5. Inter-species ordinary watermelons Because seedless watermelon pollen does not have reproductive ability, can not play the role of pollination, and stand alone can not sit fruit, so the seedless watermelon field must interplant ordinary watermelon varieties. In general, 3 rows or 4 rows of seedless watermelon intercropping 1 row of ordinary watermelon are used as pollination plants, and the ovary of seedless watermelon is expanded mainly by the stimulating effect of pollinating pollen. The skins of the selected ordinary watermelon varieties should have distinct characteristics from those of the seedless watermelon varieties in order to distinguish them from the seedless watermelons during harvesting. 6. The high-section melon seedless watermelon has a low fruit setting, not only small fruit, unfavorable fruit shape, thick skin, but also many kinds of seed shells, and colored hard shells, hollow and cracked fruit. Fruits that are suitable for fruit setting are larger in size, attractive in shape, with a thinner skin and less pods, and are not easily hollow or cracked. In the production, generally choose to leave the third female flower on the main stem (around the 20th) to stay in the melon. 7. Appropriate early harvesting of seedless watermelon is more stringent than regular watermelon. Production is usually harvested earlier than ordinary watermelon. If the harvesting is too late, the fruit is likely to be hollow or fall, the flesh is easy to grow and become soft, the juice is reduced, the flavor is reduced, and the quality is obviously reduced. It is generally more suitable for 90% to 95% ripening. (b) Exposed cultivation points The requirements for selecting soil, soil preparation and fertilization for seedless watermelons are higher than those for ordinary watermelons, and fertile sandy loam soils are preferred. Do not choose to repeat the election, requiring an interval of 6 to 8 years. The melon field was deeply turned before the winter, and the melon ditch was excavated at a 1.8-meter row spacing. 20 to 30 days before planting, flat ditch for sorghum, combined with flat ditch applied to basal fertilizer, per acre soil compost fertilizer 4000 to 5000 kilograms, superphosphate 40 to 50 kilograms, and ditch mix evenly. The noodle can be made into a turtle or flat file. 7 to 10 days before sowing or planting 2. Seeding Seedling Seedling watermelon Seedling period is approximately 40 to 45 days, and the seedling period is approximately 35 days. Therefore, the seeding period for nursery should be approximately 35 days before planting. Seeds are sown before sowing, then disinfected, soaked, and “shelled” germination (see the section on “cultivating strong seedlings” for details). During germination, the soaked seeds may be wrapped with a wet cloth, or two times the amount of the seed is clean and moist, and the sand and sand are mixed and placed under conditions of about 33° C. to germinate. Seedlings of seedless watermelons are similar to ordinary watermelons, but the seedbed temperature should be slightly higher than that of ordinary watermelons. In addition, after unearthed watermelons are unearthed, “hats” (cotyledons excavated from shells) often occur. Therefore, they must be picked in time. Cap" work. "Pick off the cap" should first spray some water, make the seed coat softened and then slowly removed, avoid dry hard crust. 3. Transplanting and planting seedless watermelon seedlings require high temperature for growth and development, are not tolerant to low temperatures, and are particularly resistant to frost. Therefore, open cultivation must be planted after the final frost. Seedless watermelon is a hybrid, with heterosis, plant growth, stems and leaves luxuriant, melon section high, mature late, so should be appropriate sparse. Line spacing is 1.8 meters and 0.6 to 0.7 meters, 550 to 620 per acre. Using double or triple vine pruning method. Before planting, open the hole according to the predetermined spacing, apply about 1 kilogram of soil-fertilizer per hole, plant the seedling into the hole, pour the planting water, and seal the soil according to the actual conditions. When planting a seedless watermelon, at the same time, 1/3 or 1/4 of the average watermelon was interplanted. If the seedless watermelon planting area is large or the bee source is abundant, the proportion of ordinary watermelon can be appropriately reduced. 4. Top dressing water dressing is divided into 3 to 4 times. For the first time when extending vines, 60-80 kilograms of cake per mu, or 750-1,000 kilograms of dry manure, is applied to the ditch at the side of the plant by 20 cm. The second time when the fruit set was established, 10 kg of urea and 15 kg of potassium sulfate were applied per acre. The method was the same for the first time. The third and fourth times were applied in the swelling period, combined with water irrigation and application, a total of 15-20 kg of urea and 10 kg of potassium sulfate. Seedless watermelon from the colonization to fruit ripening, the general must be watered 6 to 8 times, start pouring half a day of water and amplification of water than normal watermelon 4 to 5 days later. Increase the amount of water after fruiting. (3) Protecting cultivation points The protected cultivation of seedless watermelon is of great significance to enriching the varieties and supply special needs of the off-season fruits. Under the protection conditions, it is possible to artificially create the optimum environment for the growth of watermelons, and to reduce and avoid the adverse effects of natural rabbit climate. This will increase the yield of seedless watermelons and improve their quality. 1. The cultivated form of protected cultivation can be divided into double film covering cultivation, greenhouse cultivation, greenhouse cultivation and other forms, of which greenhouse cultivation is more extensive. The use of greenhouses in the production of seedless watermelons, the use of thin tubes or bamboo-arc assembly of circular arches. 2. It is best to choose small-sized and moisture-resistant varieties for the cultivation of fine-cultivated greenhouses, because these species generally have smaller shoots, more female flowers, and fruit set-up, which is suitable for dense planting. At present, seedless No. 3 and Changle seedless can be used in greenhouse cultivation in our country. 3. Cultivate watermelon in strong seedling greenhouses. The suitable colonization period in North China is in late March. If the greenhouse is covered with a shed and covered with plastic film, or if there are heating conditions, it can be advanced to mid-March. According to the appropriate seedling age of 35 days, the appropriate seeding period is at the beginning of February. Using warming seedbeds, greenhouses and other nursery. At the seedling stage, appropriate temperature and humidity are controlled, and appropriate ventilation and ventilation are carried out to cultivate strong seedlings with 3 to 4 true leaves. 4. Strengthen the management of seedlings after planting, strengthen the insulation work, maintain a high temperature, and promote its rapid seedlings. It can cover the mulch and mulching grass on the surface of the mulberry, which can increase the temperature of the soil, promote the development of the root system, prevent the evaporation of water and inhibit the growth of the weeds, and has a great impact on the future yield. Extend the vine before, in order to promote the main; after vines have to be appropriate to control the amount of fertilizer and water, promote control combined to prevent leggy. In a confined greenhouse, prolonged exposure to temperatures above 30°C and temperatures below 18°C ​​are not conducive to plant growth and fruit setting. Therefore, attention should be paid to ventilation and cooling in sunny hot weather, and thermal insulation should be strengthened in cloudy and cold weather. During flowering and fruit setting, ordinary watermelons were used for artificial pollination of seedless watermelons, and large skylights were used to improve light conditions. Carbon dioxide fertilization could also be carried out so that the plants could maintain high assimilation during the day. (D) Other Methods for Producing Seedless Watermelons 1. Natural hormone method This method is based on the fact that watermelon has the characteristics of “partial fruiting” and utilizes natural hormones contained in less seed (tetraploid) watermelon flowers to stimulate diploid seeded watermelon ovaries so that no fertilization process occurs. Through its intrinsic physiological effects, it promotes the common (diploid) watermelon plants to sit on melons and grow into seedless watermelons, which is a new way to rapidly produce seedless watermelons. It has the characteristics of easy material acquisition, simple method, and convenient operation. It can produce watermelon without seeds, and its shape is correct, thin and not hollow. The texture and flavor of watermelon is the same as the original ordinary watermelon, and it does not grow from maturity to maturity. Special cultivation measures are needed to avoid problems such as low seed germination rate, low seedling rate, and low seed setting rate. Hubei Academy of Agricultural Sciences has proved through many years of experiments that the seedless watermelon produced by this method is similar to the triploid seedless watermelon, and the fruit contains only white and tender edible pod seeds, no hollow, and contains 9% of cerium. ~ 10%, skin thickness and flavor are the same as the selected ordinary watermelon varieties. According to the test results, the seedless watermelon produced by using Xingcheng Red as the female parent was the best. It showed thin skin, crisp flesh, high sugar content, good flavor, and small white seeds. Mibao and Dujiang No. 3 watermelons are the mother-family-produced seedless watermelons. The specific production techniques are as follows: (1) Parents are selected: The seedless watermelon is selected as the parent, and the number of seeds in the fruit is required. Pollen Good quality varieties, and require plants to grow robustly. The ordinary watermelon selected as a female parent requires a small number of seeds in the fruit, a thin fruit, a high sugar content, and a high quality variety, and requires that the plants grow robustly. (2) Timely pollination: Male flowers selected as the male parent and female flowers selected as the female parent must be bagged or artificially protected in the afternoon of flowering. When the male and female flowers are opened the next morning, the male flowers are removed in time to remove the bagging or restraint, and artificial pollination is performed on the female flowers. The pollination should be performed fully and carefully so as not to damage the female flowers. After the pollination is completed, the female flowers are still bagged or bunched to prevent the pollen falling onto the stigma. After 3 days of general pollination, the juveniles should remove the bags in time in order to promote the normal growth and development of the young melons. (3) Remove the alien melon: In the melon field that uses natural hormones to produce seedless watermelons, the melons should be left to inspect the melon fields after sitting. The melons naturally sitting without artificial pollination should be removed in time to prevent the generation of abnormal melons and seeded watermelons. . Otherwise, due to the strong competitiveness of ordinary watermelon, the competitiveness of the hormone watermelon growth is weak, causing the young melons to grow little or to melon. (4) Strengthen the management of fertilizer and water: Since the seedless watermelon produced by the stimulation of natural hormones grows from the unfertilized embryos, its growth and development are relatively fragile, and it is necessary to give good fertilizer and water conditions and strengthen the finishing work to promote its normality. The growth and development. (5) Timely harvesting: The seedless watermelons produced by this method, the suitable harvesting period for mid-maturing varieties is about 30 days after flowering, the harvesting is too early, the sugar content is not high, the quality is not good, and the harvest is too late. The scorpions in the fruit increase, affecting the taste. After harvesting, the seedless watermelon should be sold or eaten immediately, and it is not easy to store for a long time, otherwise the seeds in the fruit become hard and the quality deteriorates. 2. Synthetic hormone method has proved that the use of certain hormone substances for artificial induction, can also make ordinary diploid watermelon melons, and the formed watermelon also only contains embryoless white tender seed coat, eats like seedless Like watermelon. The specific production key points are: (1) Selection of fine varieties: Tests have shown that early flowers are currently excellent varieties that use artificial synthetic hormones to produce seedless watermelons. At other times, the rate of seedless melons could reach 90%. Seed watermelons produced by artificial artificial pollination are basically the same. Other varieties such as Zhengzhou No. 3, Lemi No. 1, Zhongyu No. 6, Lujiang No. 1 and so on are also better. (2) Treatment method: First, 100 mL of sodium naphthate, 25 ppm of gibberellin, and 25 ppm of 2,4-D are separately mixed with distilled water. The female flowers of watermelon were treated with an equal mixture of these three solutions (mixed ratio of 1:1:1). Mixing fluid requirements with the use of mixing, mixed up after the day. The method of dealing with female flowers is to protect the female flower in the afternoon the day before the opening of the flower (such as for the hermaphrodite flowers should be strictly castrated), the next morning when the female flowers open, take off the bag or tie, use the new The mixture of brush pen and trowel was applied to the base of female stigma and ovary, and the dose of each flower was about 1 ml. After application, the corolla must still be clamped or bagged. On the fourth day after the application, the bag was removed, and a mixture was applied or 20 ppm of cytokinin 6-furanoaminopurine solution was applied, which had a significant effect on increasing the rate of becoming melon. Tests have shown that it is ideal to treat the second female flower of the main vine (double vine pruning). Applicators should be selected for sunny days, such as rain after applicator, and should be reapplied after rain. (3) Fine field management: Plants are required to be robust before flowering. After the application of the drug, the side vines and growing points at the leaves of the main vine are immediately removed, and the vines are pressed to promote the transfer of nutrients into the guava. After the first application of the drug, if it is found that the skin color of the young larvae is dark, it is necessary to make up the coating one time, which can effectively prevent the melon from becoming melon. About 10 days after the first application, the second growing point of vines can be removed. The two vines of the same plant should not retain untreated baby larvae, because there are seed melons and seedless melons on one plant at the same time, nutrients are easily competed by the seed melons, causing seedless melons to melon. Remove other female flowers in time to prevent them from sitting. About 12 days after the first applicator treatment, it reaches a safe period and should be watered and topdressed. However, the amount of watering should not be too large. It is advisable to use a small amount of water for pouring. Normally, it can be poured every 3 to 4 cubic meters per acre and poured every 2 to 3 days. Topdressing should be carried out on the side of the plant to open the ditch, applying 30 to 40 kg of compound fertilizer per acre. 3. For the cutting cultivation method, please refer to the section "Cultivation and Cultivation". 4. Tissue Culture Tissue culture is the use of a certain part of a plant tissue or organ to cultivate a complete plant under aseptic conditions. China began to carry out this work in 1979. Many units in Shanghai, Beijing, Shandong, Hebei, Shanxi, Gansu, and Heilongjiang have already used this method to produce a large number of high-quality, high-yield seedless watermelon supply markets, achieving remarkable results. Economic and social benefits. The specific methods are: (1) Culture materials: According to domestic and foreign reports, the embryos, shoot tips, root tips, pollen, and ovary of watermelon can all be used for tissue culture, but the most commonly used is the culture of embryos and stem tips. . (2) Culture medium: The materials used for the culture genes of the watermelon tissue culture and the different phases of the culture. Generally can be divided into three kinds of bud differentiation medium, embryo culture medium and rooting medium. 1 Watermelon bud medium: There are large amounts of ammonium nitrate (NH4NO3) 500 mg, potassium nitrate (KNO3) 1000 mg, calcium chloride (CaC12) 440 mg, and magnesium sulfate (MgSO47H2O) 370 mg per liter. Hydrogen Potassium (KH2PO4) 370 mg, Iron Salt EDTA-Na2) 745 mg; Trace Elements Ferrous Sulfate (FeSO47H2O) 55.7 g, Manganese Sulfate (MnSO44H2O) 22.3 mg, Boric Acid (H3BO3) 6.2 mg, Potassium Iodide (KI) 0.83 mg 0.25 mg of sodium molybdate (Na2MoO42H2O), 8.6 mg of zinc sulfate (ZnSO47H2O), 0.025 mg of copper sulfate (CuSO45H2O), 0.025 mg of cobalt chloride (CoC126H2O); contains 100 mg of inositol, 0.4 mg of vitamin B1, and vitamin B60 .5 mg, glycine 2 mg, nicotinic acid 0.5 mg; 1 mg of IAA; 0.5 mg of 6-benzyl purine (6-BA); 7 g agar, 30 g of sucrose or 50 g of white sugar . The pH was adjusted to 5.5-6.4. 2 Watermelon embryo culture medium: a large number of elements, trace elements, vitamins, and organics are all the same as 1, but hormones such as indole acetic acid (IAA) and 6-benzyl purine (6-BA) are removed. Sucrose was changed to 20 grams per liter (33.3 grams of white sugar). The pH was adjusted to 6-6.4. 3 Watermelon rooting medium: In addition to removing the hormone 6-benzyl purine and indole acetic acid in 1, use 1 mg of indole butyric acid (IBA). The rest of the elements are exactly the same as 1. (3) Culture method: First sterilize the culture material. If seeds are obtained, they are first soaked in warm water of 70-80°C, stirred to about 30°C, soaked for a day and night, then sterilized with 75% alcohol for 30 seconds, and the seed coats are peeled off under sterile conditions, using 0.1% of the open weight. Mercury was disinfected for 2 minutes, washed with sterile water for 4 to 5 times, inoculated on culture medium, and placed in a culture room for cultivation. The radicles first germinated, and when the two cotyledons were turned green two weeks later, the embryos with the cotyledons were excised and transferred for culture. After every 3 to 4 weeks, the apical buds and lateral buds were separated and subcultured. If direct shoot tip or lateral shoots are taken from field triploid watermelon seedlings, the material should be rinsed with tap water, then sterilized with 75% alcohol for 10 seconds, and then disinfected with 0.1% mercury. Finally, rinse with sterile water 4 to 5 times, inoculate on the culture medium, and put it into the culture room. (4) Culture medium and culture conditions: The basic medium used was M5 and 1/2 MS. According to the specific requirements for different stages of seedling differentiation, growth and rooting, different hormones were added, and 3% sucrose was added. 0.7 % of agar, adjust the pH to 5.8. The paste was autoclaved at a pressure of 1 kg/cm2 for 20 minutes, and then inoculated. The inoculated explants were then cultured in a culture chamber at a temperature of 261°C, a light intensity of 1000 lux, and an illumination of 14 hours/day. (5) Grafting and management: Tissue culture and propagation of buds can be directly cultivated into seedlings for production, and can also be used for grafting and cultivation into grafted seedlings for production. The latter is better. If grafted seedlings are grown, differentiated shoots need to be raised before grafting. The method was to transfer the shoots to the MS+IBA0.5-1.0+GA0.5 rooting medium without kinetin so that the base of the shoots gradually rooted. With the growth of the roots, the young shoots were rapidly increased and the growth was robust. , improve the quality of the scion. The rootstocks used for grafting are sown in plastic nutrient bowls filled with common soil. When the rootstock leaves are unfolded and the true leaves are slightly exposed, the top buds of the rootstocks are removed for grafting. For the selection of rootstocks and their grafting methods, see the "Cultivation" section. Immediately after grafting, it was transferred to the healing shed for healing. The temperature in the shed was 25-35°C and the relative humidity was over 95%. Under this condition, the grafted seedlings generally healed after about 10 days, then they were transferred to the greenhouse and exercised for 3 to 4 days. . This period should pay attention to ventilation, so that it gradually enhance the adaptability. Finally transplanted to Daejeon. The field cultivation management measures are similar to the seedless watermelon cultivation management measures and can be implemented by reference. (5) The solution to the "three lows" of seedless watermelons The seedless watermelons have the characteristics of good health, disease resistance, high sugar content, and convenient food. They are very popular among the people. However, due to the problems of low seed collection, low germination rate, and low seedling rate in the production of seedless watermelons, it has seriously hampered the development of production. This is also a problem to be solved in the production of seedless watermelons at home and abroad, and all localities are exploring ways to solve them. 1. Reasons for the "three lows" of the seedless watermelon (1) The main reason for the low seed collection 1 The number of chromosomes in the father and the mother is different: The triploid seedless watermelon is the parent of the tetraploid watermelon and the ordinary watermelon of the diploid. In the present hybrid, since the number of chromosomes in the tetraploid watermelon and the diploid watermelon gamete (sex cells produced when the organism carries out sexual reproduction) is different, after the hybridization, the chromosome is assigned to the zygote (male and female gamete fusion). The total number of new cells formed is the same, some different. That is, some zygotic chromosome pairs are normal, and some zygotic chromosomes are abnormally matched. Chromosome-matched normal zygotes develop into normal seeds, and abnormal matching of chromosomes does not form seeds. 2 The parent and the female parent have low affinity: In the male and female parent of the seedless watermelon, the cell structure and physiological activities of the stamen and pistil are obviously different from the stamen and pistil of the species. Studies in modern molecular biology have shown that the interaction between pollen and pistil needs first of all to “identify” each other. Pollen "identification substance" is the outer wall protein, and the "receptor" of the pistil stigma is the protein film on the nipple protrusion surface. If the pollen and the pistil are "acquainted" (affinity), the pollen wall will be quickly dissolved by the protein on the stigma. Put the pollen tube into the stigma. If the pollen and pistil are not "acquainted", the stigma mastoid then produces enamel (crust), obstructing penetration of the pollen tube. Therefore, due to the low affinity of the male parent and the female parent, affecting the germination of the pollen on the stigma and obstructing the elongation of the pollen tube is also an important cause of the lack of seeds. (2) The main reason for the low seed germination rate is that a kind of skin is thick: the seed coat of seedless watermelon is 1.5 times thicker than ordinary watermelon, and the umbilical part is thicker, about twice as much as ordinary westerly wind, and it is difficult to absorb water. At the same time, the thicker the umbilicus, the greater the resistance to germination when germinating, and the more difficult it is to germinate. Embryo malformation: Seedless watermelon seeds have 40 to 50% of embryo development defects (leaflet folds or defects), while embryos are not full, embryo weight only accounts for 34 to 38% of the seed weight, lower than ordinary watermelon About 20%. 3 Requirements for high germination requirements: Seedless watermelon seeds require higher germination than normal watermelons. For example, the germination temperature is 32 to 35°C, which is 3 to 5°C higher than that of normal watermelon. Seedless watermelon seeds breathe strongly when they germinate, they absorb water quickly and have a large amount of water. Therefore, it requires high humidity and suitable oxygen content. If the conditions are insufficient, it will affect germination. (3) Reasons for low rate of seedling formation 1 Poor seed quality: Seeds of seedless watermelon are not abundant, and the nutrients stored in the cotyledons are insufficient. Even if the seed germinates, it cannot easily meet the nutrient requirements of the sprouts. 2 Strict requirements for seedling techniques: Seedless watermelon seed has weaker top soil ability. If sowing is too deep, the cotyledons are unearthed very slowly, and sometimes they grow obliquely in the soil and cannot extend beyond the soil surface. The seeding is too shallow, the seeds are “capped” out, or the temperature after seeding is low, the young shoots grow slowly, the seed coats are not easy to fall off on their own, and the cotyledons are often caught, often not becoming seedlings. 2. Overcome the "three low" measures to synthesize the test results from all over the world and overcome the problems of low seed-collecting watermelon seed collection, low germination rate, and low seedling establishment rate. The following effective measures can be taken: (1) Artificial pollination-assisted pollination: seedless watermelon seed production When using the mixed pollen of the common male watermelon (the pollen of a single plant of the same species), artificial pollination is performed on the female tetraploid watermelon to make more ideal pollen fall onto the stigma, increasing the germination rate of the pollen, and promoting The rapid growth of the pollen tube successfully completes fertilization, thereby increasing seed production. (2) Increase of phosphate fertilizer: According to the research of the Institute of Fruit Trees of the Chinese Academy of Agricultural Sciences, the average yield per unit area of ​​applied phosphate fertilizer increased by 12.2 to 25% compared to the area without phosphorus application. Shandong Changle County Fruit Company has tested that 8Og of calcium phosphate is applied per mu, which is 31.3% higher than the increase without applying phosphate fertilizer. Phosphorus can not only increase the seed yield of the maternal tetraploid watermelon, but also increase it by four times. Seed pregnancy, promote the development of embryos, increase seedless watermelon seed weight, germination rate and seedling rate, have a more significant role. (3) Appropriate amount of boron: According to Yin Wenshan and other studies, boron application has a good effect on improving the seed-free watermelon seed pregnancy and increasing its seed-collecting amount. Add 2 mg borax per kilogram of nutritious soil during nursery, and spray 0.05% boron solution from pregnant bud to flowering interval 7 days. The yield per mu was 53.4% ​​higher than the control. (4) Proper close planting: Density planting is an important way to increase seed production. In the preparation of seedless watermelon seeds, according to the characteristics of the tetraploid watermelon short internodes, fewer branches, and more stable fruit set, can increase the number of plants and more than appropriate retention melon. According to local trials, 6O0 to 700 plants per mu, leaving 2 to 3 melons per plant, increased seed production by about 20 to 30% per mu of about 500 plants. But the planting density must not be too big. More than 900 strains per acre, or more than 4 strains per plant, resulted in excessive dispersion of nutrients, resulting in multiple small fruit, more sterile seeds, and reduced germination rates. (5) "Breaking" germination: Artificial shelling is a simple and effective measure to increase the germination rate of seedless watermelons. Generally, it can improve the germination rate by 3 to 4 times compared with the non-shelled ones. It can be broken after shelling, or it can be soaked after shelling. If soaking seeds after shelling first, the soaking time should be shortened and it should be less than 3 hours. Otherwise, due to direct water into the seed coat, resulting in long-term accumulation of seed water, but will reduce the seed germination rate. In addition, under the condition of good seed quality, the seed germination rates of the above two methods are not significantly different, but when the seed quality is poor, the germination rate of the “break” is higher than that of the “break” after the first soaking. The worse the germplasm, the greater the difference. (6) Improvement of cultivation conditions: The growth and development of seedless watermelon requires sufficient nutrients and good environmental conditions. Must be soaked before sowing germination, if the live seed, more than 90% do not emerge. Use hotbed nursery as much as possible. Careful management after sowing, such as shallow sowing, staged soil cover, suitable seedbed temperature, watering chemical fertilizer solution, etc., are conducive to seedless watermelon seed germination and seedling growth. Ordinary watermelon is generally sown at a depth of 1.5 cm, and seedless watermelons should be sown about 1 cm. In order to prevent the root system from being too shallow and the seeds “cap” unearthed, a layer of 0.5 cm thick fine soil may be sprinkled on top of the seed. The nursery technique is similar to ordinary watermelon, but the seedbed temperature should be higher than normal watermelon. The experiment showed that pouring chemical fertilizer solution into the seedbed has obvious promoting effect on seedless watermelon seedlings. The aqueous fertilizer solution can be made of 0.2% urea + 0.2% potassium dihydrogen phosphate, or 0.05% ammonium sulfate + 0.04% ammonium sulfate + 0.15% superphosphate; it is sprayed on the seedbed for about 20 days after emergence. After 8 to 10 days, colonization can be performed by spraying once again with the same concentration of the chemical fertilizer solution.

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