Seedling raising method for improving survival rate of watermelon grafted seedlings in high-temperature season

Abstract

The invention belongs to the field of vegetable and fruit seedling raising, and particularly relates to a seedling raising method for improving the survival rate of watermelon grafted seedlings in high-temperature seasons. The seedling raising method for improving the survival rate of the watermelon grafted seedlings in the high-temperature season comprises the following steps: S1, variety selection; s2, preparation before sowing; s3, sowing the seeds; s4, accelerating germination; s5, management before grafting; s6, grafting; and S7, management after grafting. After the seedling raising method is implemented, the grafting survival rate of the grafted seedlings is larger than 95%, the height of the hypocotyl of the scion is lower than 2 cm, the proportion of middle and small seedlings is lower than 3%, the grafted seedlings grow well, technical support is provided for efficient cultivation of two crops in one year for medium and small watermelons in the Yangtze River Delta region, and good economic benefits are achieved.

Description

Technical Field

[0001] The present invention belongs to the field of vegetable and fruit seedling raising, and particularly relates to a seedling raising method for improving the survival rate of watermelon grafted seedlings in high-temperature seasons. Background Art

[0002] As a major global producer and consumer of watermelons, China has an annual planting area of over 22 million mu, with a total output close to 100 million tons, occupying a prominent position in the global watermelon industry. Correspondingly, the demand for seedlings is also increasing day by day. According to the conventional cultivation mode, at least 600 seedlings are required for each mu of watermelon planting, which means that the total annual demand for watermelon seedlings in the country is as high as about 13 billion. With the wide application of grafting cultivation technology in watermelon planting, the market demand for grafted seedlings is growing rapidly at a rate of about 10% per year. Especially in the East China region, the two-season watermelon cultivation mode is gradually emerging, which makes the importance of summer grafting seedling raising increasingly prominent. Summer grafting seedling raising can not only bring higher economic benefits to the watermelon industry but also meet the market demand for high-quality watermelons, further enhancing the economic and social benefits of the entire industry.

[0003] However, there are many technical problems and management challenges in watermelon grafting seedling raising in high-temperature seasons. First of all, the low grafting survival rate is one of the most prominent problems in the high-temperature seedling raising process. In a high-temperature environment, the water evaporation rate accelerates, and the grafting wounds are prone to water loss, seriously affecting wound healing. At the same time, the respiratory rate of plants increases under high-temperature conditions, and the nutrient consumption rate accelerates, which is not conducive to the recovery and growth of grafted seedlings, resulting in a significant decrease in the grafting survival rate. Secondly, the environmental management is difficult. High temperature will cause the transpiration of grafted seedlings to be too strong, and wilting is likely to occur. Moreover, a relatively high humidity needs to be maintained during the grafting healing process to promote wound healing, but this will increase the difficulty of ventilation and cooling management and pest and disease control in summer. Furthermore, the seedlings are prone to excessive growth during the seedling stage. When raising seedlings in high-temperature seasons, the growth rates of the rootstock and scion accelerate, especially the control of the height of the hypocotyl becomes more difficult. Compared with seedling raising in winter and spring, higher requirements are imposed on the control of the hypocotyl height, otherwise, the quality of grafted seedlings and subsequent growth will be affected; for example, Chinese Patent Application CN106561283A discloses a method for grafting black beauty watermelon onto black-seeded pumpkin. Although this grafting method can improve the survival rate of seedling formation, it does not control the height of the hypocotyl, so the subsequent growth of grafted seedlings is difficult to predict. Finally, pests and diseases are likely to occur. The high-temperature and high-humidity environmental conditions provide favorable conditions for the breeding and reproduction of pests and diseases. The occurrence frequency and damage degree of diseases such as powdery mildew, stem rot, anthracnose, and pests such as thrips, whiteflies, aphids, and spider mites have increased significantly, bringing huge challenges to the seedling raising work. These technical problems not only restrict the large-scale development of watermelon grafting seedling raising in high-temperature seasons but also affect the quality and production benefits of grafted seedlings.

[0004] At present, the existing seedling raising technologies have obvious deficiencies in dealing with many problems of watermelon grafting seedling raising in high-temperature seasons. Therefore, developing a seedling raising method that can effectively solve the problems of watermelon grafting seedling raising in high-temperature seasons is of extremely important practical significance for improving the survival rate and quality of grafted seedlings and ensuring the sustainable development of the watermelon industry. Summary of the Invention

[0005] To solve the problems existing in the prior art and respond to the market demand for watermelon grafted seedlings, the present invention provides a seedling raising method for improving the survival rate of watermelon grafting in high-temperature seasons. Through the reasonable optimization of variety selection, substrate ratio, and grafting time, as well as steps such as seed pretreatment, seedling raising environment before and after grafting, water and fertilizer management, and PGR regulation, the invention aims to achieve the purpose of improving the survival rate and product quality of grafted seedlings.

[0006] To solve the above technical problems, the first aspect of the present invention provides a seedling raising method for improving the survival rate of watermelon grafted seedlings in high-temperature seasons, including:

[0007] S1. Variety selection;

[0008] S2. Preparation before sowing;

[0009] S3. Sowing;

[0010] S4. Germination acceleration;

[0011] S5. Management before grafting;

[0012] S6. Grafting;

[0013] S7. Management after grafting.

[0014] As an implementable case, the variety selection includes selecting a rootstock variety suitable for high-temperature environments and a medium-sized or small-sized watermelon variety suitable for high-temperature environments.

[0015] Further, the rootstock variety includes pumpkin.

[0016] Further, the medium-sized or small-sized watermelon variety includes one of Zaojia 8424, Meidu, Xiaolan, or Xiaohuangguan.

[0017] As an implementable case, the preparation before sowing includes the preparation of a seedling raising substrate, the selection of a plug tray, and the pretreatment of scion seeds.

[0018] Further, the seedling raising substrate includes peat and perlite, and the volume ratio of peat to perlite is (3 - 5):(2 - 3).

[0019] Even further, the volume ratio of peat to perlite is 3:2.

[0020] In the present invention, it is further specified that in summer, peat and perlite are formulated into a substrate in a ratio of 3:2. Compared with the traditional ratio of 3:1, it can significantly improve the survival rate and growth quality of watermelon grafted seedlings in the high-temperature season. By increasing the proportion of perlite to 40%, this ratio optimizes the porosity and air permeability of the substrate, effectively alleviates the problem of root hypoxia in high-temperature environments, and at the same time, the water retention capacity of 60% peat and the drainage characteristics of perlite form a dynamic balance, avoiding physiological stress caused by waterlogging and root rot or excessive water evaporation. In addition, the heat insulation characteristics of perlite can reduce the substrate temperature by 2-3°C, reduce the damage to the roots caused by high temperature, and its stable physical structure can also promote the uniform distribution of water during the graft healing period.

[0021] Furthermore, the water content of the substrate is 60-70%, the EC value is <0.8 mS / cm, the pH value is 5.5-6.5, and the fiber length is <10 mm.

[0022] As an implementable case, the color of the plug tray is non-black.

[0023] Furthermore, the color of the plug tray is white.

[0024] When carrying out watermelon grafting and seedling raising in a high-temperature environment in summer, the selection of the plug tray is of great significance for ensuring the seedling raising effect. It is advisable to avoid choosing black plug trays as much as possible because black plug trays have strong heat absorption and are prone to absorbing a large amount of heat under high-temperature conditions, which will then lead to a significant increase in the substrate temperature. Excessive substrate temperature will have many adverse effects on root growth, such as inhibiting the normal metabolic activities of the roots, causing the roots to grow slowly or even stagnate, reducing the root's ability to absorb water and nutrients, and ultimately affecting the overall growth and development of the grafted seedlings. In severe cases, it may also cause root burns or death, increase the risk of disease occurrence, and affect the graft survival rate and seedling raising quality. In contrast, choosing a non-black plug tray is more suitable. White plug trays have weak heat absorption, can effectively reduce heat absorption, and reduce the amplitude of the increase in substrate temperature, thus creating a relatively stable and suitable growth environment for the roots, contributing to the normal growth and development of the roots, and enhancing the stress resistance and survival rate of the grafted seedlings.

[0025] As an implementable case, in the pre-treatment of the scion seeds, the soaking temperature of the seeds is 50-60°C, and then it is naturally cooled for soaking treatment.

[0026] Furthermore, in the pre-treatment of the scion seeds, soak the seeds in warm water at 55°C, with the water consumption being about three times the amount of the seeds, stir continuously, wait for it to cool naturally to room temperature of 25°C and then soak for 12 hours; after the soaking ends, rinse with clean water twice, rub off the mucus on the seed surface, drain the water, put the seeds into a square tray, and cover them with a clean wet cloth to keep them moist.

[0027] As an practicable example, the sowing process includes rootstock sowing and scion sowing.

[0028] Furthermore, the rootstock sowing includes: in June, pumpkin rootstocks are sown 40 days before the product is released from the nursery, 20 days earlier than in winter and spring; from July to September, pumpkin rootstocks are sown 35 days before the product is released from the nursery, 15 days earlier than in winter and spring; pumpkin rootstocks do not need to be soaked, and manual or mechanized sowing is adopted, one seed per hole, and the moisture content of the substrate is controlled at 60-70%.

[0029] Furthermore, the scion sowing includes: evenly sowing the soaked watermelon scion seeds on a square tray with a sowing density of 600 seeds / tray; when top grafting is adopted, the scion is sown 5 days later than the rootstock in June, and 3 days later than the rootstock from July to September; when applique grafting is adopted, the scion is sown 7 days earlier than the rootstock in June, and 5 days earlier than the rootstock from July to September.

[0030] As an implementable case, the germination includes rootstock germination and scion germination.

[0031] Furthermore, the rootstock germination includes placing the pumpkin rootstock in a germination room after sowing, with a germination temperature of 28-30° C. and a relative humidity of ≥90%. The pumpkin rootstock germination time in a high temperature environment in summer is 48 hours.

[0032] Furthermore, the scion germination includes: the watermelon scion germination temperature is 28-30° C., the relative humidity is ≥90%, and after germination for 72 hours, that is, when the cotyledons push out of the substrate surface, the scion is moved into a greenhouse.

[0033] As an implementable case, the pre-grafting management includes rootstock cultivation and scion cultivation.

[0034] Furthermore, the rootstock cultivation includes: a rootstock seedling raising period before grafting, which is 12-18 days in June and 8-12 days from July to September, with a day and night temperature difference treatment; when 80% of the rootstock seeds are above the soil, spray 100 mg / L of paclobutrazol once to control the height, and after the seeds are completely germinated and neatly, spray 50 mg / L of paclobutrazol once; after the cotyledons of the rootstock are flattened, fertilizer with a nitrogen, phosphorus and potassium ratio of 15:0:15 and a concentration of 800 times is applied, and the frequency is maintained every other day.

[0035] Furthermore, the scion cultivation includes: the scion seedling raising period before grafting is 5 - 10 days, with day-night temperature difference treatment; when the light intensity exceeds 30000 Lux, shade and cooling are achieved by building a small arch shed, and a sunshade net with a shading rate > 70% is used; after one week when the cotyledons dehull and turn green, spray 800-fold solution of propamocarb hydrochloride, 1000-fold solution of kasugamycin, and 1500-fold solution of Fig, and the volume ratio of the 800-fold solution of propamocarb hydrochloride, 1000-fold solution of kasugamycin, and 1500-fold solution of Fig is 1:1:1; wait for grafting.

[0036] Furthermore, in the day-night temperature difference treatment, the daytime temperature in summer is 26 - 30 °C, and the nighttime temperature is 16 - 20 °C.

[0037] In the present invention, the daytime temperature in summer is limited to 26 - 30 °C, and the nighttime temperature is 16 - 20 °C to simulate the natural temperature difference and balance photosynthesis and respiration. A relatively high daytime temperature promotes the synthesis of organic substances through photosynthesis, while a relatively low nighttime temperature reduces the consumption through respiration, which is beneficial to nutrient accumulation, promotes the healing of grafting wounds, and enhances stress resistance. Ultimately, it improves the grafting survival rate, makes the grafted seedlings stronger, ensures balanced growth, and improves the overall quality.

[0038] As an implementable case, the grafting includes: grafting time selection, grafting preparation, and grafting treatment.

[0039] Furthermore, the grafting time selection includes: performing grafting operations in summer, and selecting the periods of 7:00 - 11:00 and 14:00 - 20:00.

[0040] In the present invention, the grafting time is selected during 7:00 - 11:00 and 14:00 - 20:00 to avoid the high-temperature period at noon. This is mainly because the high temperature at noon will accelerate the water evaporation of the grafting wound, resulting in too fast water loss from the wound and affecting healing. Grafting during a relatively cool period can not only reduce the water evaporation of the wound but also reduce the interference with the physiological activities of the plant, helping the plant better adapt to the environment after grafting, thereby improving the accuracy and survival rate of the grafting operation.

[0041] Furthermore, in the grafting preparation, the grafting tools include a blade, a bamboo stick, and an operating table, and large-scale grafting adopts a flow-line operation. Disinfect the grafting tools and the operating table with alcohol or 1500-fold solution of Amistar; before grafting, cut off half of each of the two cotyledons of the pumpkin rootstock to control the growth trend of the rootstock seedling stage.

[0042] Furthermore, the grafting treatment includes top plug grafting or patch grafting.

[0043] Furthermore, the top plug grafting includes: the scion is sown 5 days later than the rootstock in June and 3 days later than the rootstock from July to September; remove the base of the first leaf of the pumpkin rootstock together with the growing point, and use a bamboo stick to obliquely insert a hole along the base of the midrib of one cotyledon to below the petiole of the midrib of the other cotyledon at an angle of 40°-50°, with a depth of 5-10 mm; symmetrically cut the scion at 1-1.5 cm below the petiole of the cotyledon of the scion with a blade to form a wedge shape with two cut surfaces; obliquely insert the cut scion into the bamboo stick insertion hole of the rootstock, ensuring that the cotyledons of the scion and the cotyledons of the rootstock are in a cross shape.

[0044] Furthermore, the approach grafting includes: the scion is sown 7 days earlier than the rootstock in June and 5 days earlier than the rootstock from July to September; the rootstock is sown 5 days later than the scion in June and 3 days later than the scion from July to September; the appropriate grafting period is when the cotyledons of the rootstock and the scion are flat and just showing true leaves; use a grafting knife to remove the growing point of the rootstock and obliquely cut downward at an angle of 20°-30° from the growing point, with a knife edge length of 0.5-1 cm; obliquely cut downward at an angle of 25°-30° at 0.8-1 cm below the cotyledons of the scion, with a knife edge length of 0.5-0.6 cm; fit the cut surface of the scion to the cut surface of the rootstock stem, and fix them tightly with a grafting clip after they are closely combined.

[0045] As an implementable case, the post-grafting environmental management includes: healing environmental management, water and fertilizer management, PGR regulation, and pest and disease control.

[0046] Further, the healing environmental management includes: immediately put the grafted seedlings into a small arch shed after grafting, cool down through a spraying facility, control the daytime temperature at 26-30°C, the nighttime temperature at 16-20°C, and the relative air humidity ≥ 95%; avoid strong light for 4 to 5 days of healing. When the light intensity exceeds 30000 Lux, cover with non-woven fabric or a sunshade net, and the relative air humidity ≥ 90%. Pay attention to controlling the height of the hypocotyl of the scion; during the 6 to 8 days of healing, gradually increase the light intensity and reduce the humidity in combination with the temperature, and keep the relative air humidity at 65-75%; 24 hours after grafting, lift the film for ventilation and moisture dissipation every morning and evening. Gradually increase the film-lifting time on the 5th day after grafting until complete healing; do not apply chemical agents within 5 days after grafting to avoid affecting the survival rate of the grafted seedlings.

[0047] Further, the water and fertilizer management includes: within 5 days of grafting healing, no fertilizer needs to be applied, water as needed, and keep the water content of the substrate equal to the relative air humidity; from 6 to 8 days of grafting healing, mainly use a fertilizer with a nitrogen, phosphorus, and potassium ratio of 15:0:15, spray at a concentration of 800 times, and keep the frequency of fertilizer and water every other day. Excessive application is likely to cause excessive growth; from 11 days of healing to after the grafted seedlings survive, alternately use two fertilizers with a nitrogen, phosphorus, and potassium ratio of 20:10:20 and 15:0:15 at a concentration of 800 times. The fertilization time and frequency depend on the growth status of the grafted seedlings and the weather conditions.

[0048] Further, the PGR regulation includes: after grafting survival, applying paclobutrazol at a concentration of 80 - 120 mg / L to control plant height.

[0049] Further, the pest and disease control includes: after seed germination, spraying difenoconazole 1500 - fold solution, thiabendazole 1000 - fold solution and previcur 800 - fold solution; then 1 day before grafting, spraying bixafen 1500 - fold solution, kasugamycin 800 - fold solution and ethoxyfen 1500 - fold solution; the common pests in summer watermelon seedling stage include whiteflies, aphids, thrips and Lepidoptera pests. On the basis of physical control and biological control by hanging yellow and blue boards, combined with chemical agents such as thiamethoxam, imidacloprid, abamectin, spinetoram, flonicamid or dinotefuran for enhanced control.

[0050] Further, when the grafting treatment is top - plug grafting, the post - grafting environmental management also includes removing the tillers of the rootstock.

[0051] Furthermore, the removal of the tillers of the rootstock includes: for watermelon seedlings grafted by the top - plug method, the rootstock is prone to grow lateral buds. Starting from the 10th day of the healing period, timely remove the rootstock tillers to avoid the scion becoming weak and leggy due to insufficient nutrient supply.

[0052] Further, when the grafting treatment is patch grafting, the post - grafting environmental management also includes removing the grafting clip.

[0053] Furthermore, the removal of the grafting clip is carried out 8 - 12 days after patch grafting. When the grafting seedling wound has healed and new leaves start to grow, remove the grafting clip.

[0054] Beneficial effects

[0055] (1) By optimizing the substrate ratio, defining the peat and perlite compounded at a ratio of 3:2 as the substrate, precisely regulating the day - night temperature difference and post - grafting humidity management, the germination rate of pumpkin rootstock and watermelon scion in the high - temperature season from June to September can reach 95%, which is more than 3% higher than the common seedling - raising methods in winter and spring. The grafting survival rates of top - plug grafting and patch grafting are 97% and 95% respectively, and the seedling formation rate reaches over 90%. When the grafted seedlings are planted in Shanghai and the Yangtze River Delta region, the planting survival rate reaches over 98%, and the quality of the grafted seedlings is effectively improved.

[0056] (2) By adopting PGR regulation with paclobutrazol and reasonable water and fertilizer management, and at the same time defining the ratio of nitrogen, phosphorus and potassium elements, the height of the scion hypocotyl is less than 2 cm, and the proportion of medium and small seedlings is reduced to 2.6% - 2.9%, and the seedling growth is strong.

[0057] (3) In the present invention, by pre - treating the seeds by soaking in warm water at 50 - 60 °C, spraying fungicides before grafting and physical control with yellow / blue boards, the incidence rates of diseases and pests such as stem rot and whiteflies in high - temperature and high - humidity environments can be significantly reduced.

[0058] (4) By means of variety selection of rootstock and scion, reasonable optimization of substrate ratio, seed pretreatment, grafting method, seedling raising environment, water and fertilizer management after grafting, and PGR regulation of plant height, etc., the survival rate and seedling quality of watermelon grafted seedlings under high temperature conditions in summer are effectively improved, providing technical support for realizing two-crop high-efficiency cultivation of small and medium-sized watermelons in the Yangtze River Delta region, and achieving good economic benefits.

[0059] (5) By adopting the seedling raising method provided by the present invention, on the basis of grafting methods such as top plug grafting and sticking grafting, mechanical grafting methods such as double root cutting can be added to respond to the improvement of the mechanization level of watermelon grafted seedling production and further improve agricultural production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a flow chart of the seedling raising method for improving the survival rate of watermelon grafted seedlings in high temperature seasons provided by the present invention.

[0061] Figure 2 It is an operation diagram of top plug grafting in Example 1.

[0062] Figure 3 It is an operation diagram of sticking grafting in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] Example 1. Top plug seedling raising

[0064] This example provides a seedling raising method for improving the survival rate of watermelon grafted seedlings in high temperature seasons, specifically as follows:

[0065] S1. Variety selection: Select the pumpkin variety 'Zhenxi 316' suitable for high temperature environment as the rootstock variety, and select the small and medium-sized watermelon variety 'Zaojia 8424' as the scion variety;

[0066] S2. Preparation before sowing:

[0067] Preparation of seedling substrate: In summer, select peat and perlite to prepare the seedling substrate according to a volume ratio of 3:2, stir evenly, and control the water content of the substrate at 65%. The EC value of the substrate < 0.8 mS / cm, the pH value is 5.5 - 6.5, and the fiber length < 10 mm;

[0068] Selection of plug tray: Select a 50-hole white plug tray;

[0069] Pretreatment of scion seeds: Soak the seeds in warm water at 55°C, with the water consumption being three times the amount of seeds, stir continuously, and soak for 12 hours after it naturally cools to room temperature of 25°C; after the soaking ends, rinse with clean water twice, rub off the mucus on the seed surface, drain the water, put the seeds into a square tray, and cover with a clean wet cloth to keep moisture;

[0070] S3. Sowing:

[0071] Rootstock sowing: In June, pumpkin rootstocks are sown 40 days before the product is released from the nursery, 20 days earlier than in winter and spring; from July to September, pumpkin rootstocks are sown 35 days before the product is released from the nursery, 15 days earlier than in winter and spring; pumpkin rootstocks do not need to be soaked, and mechanized sowing is adopted, one seed per hole, and the moisture content of the substrate is controlled at 65%;

[0072] Scion sowing: Sow the soaked watermelon scion seeds evenly on the square tray at a density of 600 seeds / tray;

[0073] S4. Germination:

[0074] Rootstock germination: Summer pumpkin rootstocks do not need to be soaked. After sowing, they are placed in a germination room with a germination temperature of 29°C and an air relative humidity of ≥90%. The germination time in the high temperature environment in summer is shorter than that in winter and spring, and the germination time for pumpkin rootstocks is 48 hours.

[0075] Scion germination: The germination temperature of watermelon scion is 29℃, the relative humidity of air is ≥90%, and the germination time is 72 hours, that is, when the cotyledons are above the surface of the substrate, they are moved into the greenhouse;

[0076] S5. Management before grafting:

[0077] Stock cultivation: The stock seedling raising cycle before grafting is 15 days in June and 10 days from July to September. The temperature difference between day and night is treated during stock cultivation, with a daytime temperature of 26-30℃ and a night temperature of 16-20℃ in summer. When 80% of the stock seeds are above the soil, spray 100mg / L of paclobutrazol once to control the height. After the seeds are fully germinated and neatly, spray 50mg / L of paclobutrazol once again. After the stock cotyledons are flattened, fertilizer with a nitrogen, phosphorus and potassium ratio of 15:0:15 is used as the main fertilizer, with a concentration of 800 times liquid, and the frequency is maintained every other day.

[0078] Scion cultivation: The scion seedling raising period before grafting is 7 days. The temperature difference between day and night is handled during the scion cultivation. The daytime temperature in summer is 26-30℃, and the nighttime temperature is 16-20℃. When the light intensity exceeds 30,000Lux, shading and cooling are achieved by building a small arch shed, and a shading net with a shading rate of ≥70% is used. After one week, when the cotyledons are shelled and turn green, spray 800 times of propamocarb hydrochloride solution, 1000 times of kasugamycin solution and 1500 times of fig. The volume ratio of 800 times of propamocarb hydrochloride solution, 1000 times of kasugamycin solution and 1500 times of fig. solution is 1:1:1. Wait for grafting.

[0079] S6. Grafting:

[0080] Grafting time selection: Grafting should be done between 7:00-11:00 and 14:00-20:00;

[0081] Grafting preparation: Grafting tools include blades, bamboo sticks and operating tables. Large-scale grafting adopts flow-type operation. Use 1500 times diluted Amisida to disinfect the grafting tools and operating tables. Before grafting, the two cotyledons of pumpkin rootstock need to be cut off in half to control the growth of the rootstock.

[0082] Grafting treatment: top grafting is adopted, and the scion is sown 5 days later than the rootstock in June, and 3 days later than the rootstock from July to September; the base of the first leaf of the pumpkin rootstock is removed together with the growth point, and a bamboo stick is used to diagonally insert a hole at a 45° angle along the base of the midrib of one cotyledon to the bottom of the petiole of the other cotyledon midrib, with a depth of 8mm; a blade is used to symmetrically cut the hypocotyl 1cm below the petiole of the scion cotyledon to form a wedge with two-sided cuts; the cut scion is obliquely inserted into the bamboo stick insertion hole of the rootstock to ensure that the scion cotyledon and the rootstock cotyledon are cross-shaped;

[0083] S7. Post-grafting management:

[0084] Healing environment management: On sunny days in summer, build two layers of sunshade nets on the top of the healing area, and hang spray facilities below; put the grafted seedlings into the healing area immediately after grafting, and cool them down through spray facilities. The daytime temperature is controlled at 26-30℃, the night temperature is 16-20℃, and the relative humidity of the air is ≥95%; avoid strong light within 5 days of healing, and cover with non-woven fabrics or sunshade nets when the light intensity exceeds 30,000 Lux; pay attention to ventilation and proper lighting to control the height of the scion hypocotyl; after 6 days of healing, gradually increase the light intensity in combination with the temperature, and gradually reduce the humidity, and keep the relative humidity of the air at 70%; 24 hours after grafting, lift the film every morning and evening for ventilation and moisture dissipation, and increase the film lifting time on the 5th day after grafting until complete healing; do not spray chemical agents within 5 days after grafting to avoid affecting the survival rate of the grafted seedlings;

[0085] Water and fertilizer management: Within 5 days after grafting and healing, no fertilizer is needed. Water as needed to maintain the moisture content of the substrate and the relative humidity of the air. After grafting and healing for 6 to 8 days, use fertilizer with a nitrogen-phosphorus-potassium ratio of 15:0:15 as the main fertilizer, spray with a concentration of 800 times liquid, and keep the frequency of fertilizer and water every other day to meet the needs of the day. Too much fertilizer will easily cause leggy growth. After healing for 11 days, that is, after the grafting survives, use two fertilizers with a nitrogen-phosphorus-potassium ratio of 20:10:20 and 15:0:15 alternately, with a concentration of 800 times liquid. The time and frequency of fertilization depend on the growth status of the grafted seedlings and weather conditions.

[0086] PGR regulation: After the watermelon graft survives in summer, spray 100 mg / L of paclobutrazol to control plant height;

[0087] Removal of rootstock tillers: For watermelon seedlings grafted by top grafting, remove rootstock tillers in time starting from the 10th day of the healing period to prevent the scion from growing thin and leggy due to insufficient nutrient supply;

[0088] Pest and disease control: In the seedling stage of summer watermelons, diseases are prone to occur, including stem rot, powdery mildew and anthracnose; ventilation and humidity control are emphasized during the seedling stage to reduce the incidence of diseases; the principle of applying chemical agents is prevention first: after the seeds germinate, spray 1500-fold solution of difenoconazole, 1000-fold solution of thiabendazole, and 800-fold solution of preclozole; then 2 days before grafting, spray 1500-fold solution of bixafen, 800-fold solution of kasugamycin and 1500-fold solution of ethoxyfen; pests prone to occur in the seedling stage of summer watermelons include whiteflies, aphids, thrips and Lepidoptera pests. Hang yellow and blue boards for physical control, combined with chemical agents such as thiamethoxam, imidacloprid, abamectin, spinetoram, flonicamid and dinotefuran, and use as needed.

[0089] Figure 1 It is a flow chart of the seedling raising method for improving the survival rate of watermelon grafted seedlings in high temperature seasons provided by the present invention.

[0090] The operation diagram of the top plug grafting in this example is as Figure 2 shown.

[0091] Example 2. Seedling raising by the sticking method

[0092] This example provides a seedling raising method for improving the survival rate of watermelon grafted seedlings in high temperature seasons, specifically as follows:

[0093] S1. Variety selection: Select the pumpkin variety 'Zhenxi 316' suitable for high temperature environment as the rootstock variety, and select the medium and small watermelon variety 'Zaojia 8424' as the scion variety;

[0094] S2. Preparation before sowing:

[0095] Preparation of seedling substrate: In summer, select peat and perlite to prepare the seedling substrate according to a volume ratio of 3:2, stir evenly, and control the water content of the substrate at 65%. The EC value of the substrate < 0.8 mS / cm, pH value 5.5 - 6.5, fiber length < 10 mm;

[0096] Selection of plug trays: Select white plug trays with a specification of 50 holes;

[0097] Pretreatment of scion seeds: Soak the seeds in warm water at 55°C, with the water consumption being three times the amount of seeds, stir constantly, and soak for 12 hours after it naturally cools to room temperature of 25°C; after the soaking ends, rinse with clean water twice, rub off the mucus on the surface of the seeds, drain the water, put the seeds into a square tray, and cover with a clean wet cloth to keep them moist;

[0098] S3. Sowing:

[0099] Rootstock sowing: In June, the pumpkin rootstock is sown 40 days before the product outplanting date, 20 days earlier than in winter and spring; from July to September, the pumpkin rootstock is sown 35 days before the product outplanting date, 15 days earlier than in winter and spring; the pumpkin rootstock does not need to be presoaked, and mechanized sowing is adopted, with one seed per hole, and the water content of the substrate is controlled at 65%;

[0100] Scion sowing: Manual sowing is adopted, with one seed per hole; presoaking is carried out with warm water at 55°C, and the water consumption is 3 times the volume of the seeds. Keep stirring continuously. Wait for it to cool naturally to room temperature of 25°C. After 8 hours, rinse with clean water and drain. Evenly spread and sow on a square tray, and the sowing density is 600 seeds per tray;

[0101] S4. Germination acceleration:

[0102] Rootstock germination acceleration: The summer pumpkin rootstock does not need to be presoaked. After sowing, it is placed in a germination acceleration chamber. The germination acceleration temperature is 29°C, and the relative air humidity is ≥90%; the germination acceleration time in the high-temperature environment in summer is relatively shorter than that in winter and spring. The germination acceleration time of the pumpkin rootstock is 48 hours;

[0103] Scion germination acceleration: The germination acceleration temperature of the watermelon scion is 29°C, and the relative air humidity is ≥90%. Germination is accelerated for 72 hours. That is, when the cotyledons push out the substrate surface, it is moved into the greenhouse;

[0104] S5. Management before grafting:

[0105] Rootstock cultivation: After the rootstock comes out of the germination acceleration chamber, it is moved into the seedling-raising greenhouse for cultivation; the seedling-raising cycle of the rootstock before grafting is 15 days in June and 10 days from July to September; the temperature in summer is relatively high. The daytime temperature in the greenhouse is maintained at 26 - 30°C, and the nighttime temperature is 16 - 20°C; when the light intensity exceeds 30000 Lux, the scion is shaded as needed; during summer seedling raising, the seeds germinate quickly. After the cotyledons are flattened, fertilizers with a nitrogen, phosphorus, and potassium ratio of 15:0:15 are mainly used, and the application concentration is 800 times liquid. The fertilizer and water frequency is maintained at once every other day, and the daily fertilizer and water volume only needs to meet the demand of the day, not too much, to prevent excessive growth caused by too high nighttime temperature;

[0106] Scion cultivation: After the scion comes out of the germination acceleration chamber, it is moved into the greenhouse for cultivation. The seedling-raising cycle of the scion before grafting is about 7 days. The daytime temperature in the greenhouse is 26 - 30°C, and the nighttime temperature is 16 - 20°C. When the light intensity exceeds 30000 Lux, set up a sunshade net for shading and cooling, and the shading rate of the sunshade net > 70%; after one week, when the cotyledons remove the shell and turn green, spray 800 times of propamocarb hydrochloride, 1000 times of kasugamycin, and 1500 times of Fig, and wait for grafting.

[0107] S6. Grafting:

[0108] Selection of grafting time: Select the period from 7:00 - 11:00 and 14:00 - 20:00 for grafting;

[0109] Grafting preparation: Grafting tools include blades, bamboo sticks and operating tables. Large-scale grafting adopts flow-type operation. Use 1500 times diluted Amisida to disinfect the grafting tools and operating tables. Before grafting, the two cotyledons of pumpkin rootstock need to be cut off in half to control the growth of the rootstock.

[0110] Grafting treatment: Adopt the stick grafting method, in June, the stock is sown 7 days later than the scion, and from July to September, the stock is sown 5 days later than the scion; the grafting period is when the cotyledons of the stock and scion are flat and just exposed to the true leaves; remove the growth point of the stock with a grafting knife, and cut it downward at a 30-degree angle from the growth point, with a length of 0.5 cm; cut it downward at a 30-degree angle 1 cm below the cotyledons of the scion, with a length of 0.5 cm; fit the cut of the scion to the cut of the stock stem, so that the two are tightly combined, and then fix them with a grafting clamp;

[0111] S7. Post-grafting management:

[0112] Healing environment management: On sunny days in summer, build two layers of sunshade nets on the top of the healing area, and hang spray facilities below; put the grafted seedlings into the healing area immediately after grafting, and cool them down through spray facilities. The daytime temperature is controlled at 26-30℃, the night temperature is 16-20℃, and the relative humidity of the air is ≥95%; avoid strong light within 5 days of healing, and cover with non-woven fabrics or sunshade nets when the light intensity exceeds 30,000 Lux; pay attention to ventilation and proper lighting to control the height of the scion hypocotyl; after 6 days of healing, gradually increase the light intensity in combination with the temperature, and gradually reduce the humidity, and keep the relative humidity of the air at 70%; 24 hours after grafting, lift the film every morning and evening for ventilation and moisture dissipation, and increase the film lifting time on the 5th day after grafting until complete healing; do not spray chemical agents within 5 days after grafting to avoid affecting the survival rate of the grafted seedlings;

[0113] Water and fertilizer management: Within 5 days after grafting and healing, no fertilizer is needed. Water as needed to maintain the moisture content of the substrate and the relative humidity of the air. After grafting and healing for 6 to 8 days, use fertilizer with a nitrogen-phosphorus-potassium ratio of 15:0:15 as the main fertilizer, spray with a concentration of 800 times liquid, and keep the frequency of fertilizer and water every other day to meet the needs of the day. Too much fertilizer will easily cause leggy growth. After healing for 11 days, that is, after the grafting survives, use two fertilizers with a nitrogen-phosphorus-potassium ratio of 20:10:20 and 15:0:15 alternately, with a concentration of 800 times liquid. The time and frequency of fertilization depend on the growth status of the grafted seedlings and weather conditions.

[0114] PGR regulation: After the watermelon graft survives in summer, spray 100 mg / L of paclobutrazol to control plant height;

[0115] Removing the grafting clip: 10 days after grafting by the sticking method, when the wound of the grafted seedling has healed and new leaves have begun to grow, remove the grafting clip;

[0116] Pest and disease control: During the seedling stage of summer watermelons, diseases are prone to occur, including stem rot, powdery mildew, and anthracnose. Pay attention to ventilation and humidity control during the seedling stage to reduce the incidence rate. The principle of applying chemical agents is prevention first. After the seeds germinate, spray 1500-fold solution of difenoconazole, 1000-fold solution of thiabendazole, and 800-fold solution of previcur. Then, 1 day before grafting, spray 1500-fold solution of bixafen, 800-fold solution of kasugamycin, and 1500-fold solution of ethirimol. Pests prone to occur during the seedling stage of summer watermelons include whiteflies, aphids, thrips, and lepidopteran pests. Use physical and biological control methods such as hanging yellow and blue boards, and combine with chemical agents such as thiamethoxam, imidacloprid, abamectin, spinetoram, flonicamid, and dinotefuran as needed.

[0117] The flow chart of the seedling raising method for improving the survival rate of watermelon grafted seedlings in high temperature seasons provided by the present invention is as Figure 1 shown.

[0118] The operation diagram of grafting by the example of the stick grafting method is as Figure 3 shown.

[0119] Comparative Example 1

[0120] The specific implementation method of this example is the same as that of Example 1, the difference is that during the day-night temperature difference treatment in the rootstock cultivation, the day temperature and night temperature in summer are both 28-30 °C.

[0121] Comparative Example 2

[0122] The specific implementation method of this example is the same as that of Example 1, the difference is that the volume ratio of peat and perlite is 3:1.

[0123] Comparative Example 3

[0124] The specific implementation method of this example is the same as that of Example 1, the difference is that it does not include the PGR regulation step.

[0125] Performance test

[0126] Observe and record the growth status of the grafted seedlings in Examples 1-2 and Comparative Examples 1-3, measure their grafting survival rate, plant height, rootstock hypocotyl length, scion hypocotyl length, and the proportion of medium and small seedlings; the specific experimental results are shown in Table 1.

[0127] Table 1

[0128]

[0129] It can be seen from the experimental results in Table 1 that the grafting survival rate of the grafted seedlings in Examples 1-2 is greater than 95%, the scion hypocotyl height is less than 2 cm, and the proportion of medium and small seedlings is less than 3%. The growth of the grafted seedlings is significantly better than that in Comparative Examples 1-3.

Claims

1. A seedling raising method for improving the survival rate of watermelon grafting in high temperature seasons, characterized in that: include: S1. Variety selection: Choose rootstock varieties suitable for high temperature environment and small and medium-sized watermelon varieties suitable for high temperature environment; S2, pre-sowing preparation: preparation of seedling medium, selection of plug trays and pretreatment of scion seeds; S3, sowing: rootstock sowing and scion sowing; S4, germination: rootstock germination and scion germination; S5. Management before grafting: stock cultivation and scion cultivation; S6. Grafting: grafting time selection, grafting preparation and grafting treatment; S7. Post-grafting management: healing environment management, water and fertilizer management, PGR regulation and pest and disease control.

2. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature season according to claim 1, characterized in that: The medium and small watermelon varieties include one of Zaojia 8424, Meidu, Xiaolan or Xiaohuangguan; the rootstock variety includes pumpkin.

3. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature season according to claim 1, characterized in that: The seedling culture medium comprises peat and perlite, and the volume ratio of the peat to the perlite is (3-5): (2-3).

4. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature season according to claim 1, characterized in that: The PGR regulation includes: after the graft survives, applying paclobutrazol with a concentration of 80-120 mg / L to control plant height.

5. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature season according to claim 1, characterized in that: In the scion seed pretreatment, the seeds are soaked at a temperature of 50-60° C., and then naturally cooled and soaked.

6. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature seasons according to claim 1, characterized in that: The grafting process includes top-insertion grafting or pasting grafting.

7. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature seasons according to claim 6, characterized in that: The top-insertion grafting comprises: sowing the scion 5 days later than the rootstock in June, and sowing 3 days later than the rootstock in July to September; removing the base of the first leaf of the pumpkin rootstock together with the growth point, using a bamboo stick to obliquely insert a hole at an angle of 40°-50° along the base of the midrib of one cotyledon to the bottom of the petiole of the midrib of the other cotyledon, with a depth of 5-10 mm; using a blade to symmetrically cut the embryo axis 1-1.5 cm below the petiole of the scion cotyledon to form a wedge with cuts on two sides; obliquely inserting the cut scion into the bamboo stick insertion hole of the rootstock to ensure that the cotyledon of the scion and the cotyledon of the rootstock are crossed in a cross shape.

8. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature seasons according to claim 6, characterized in that: The grafting method comprises: sowing the scion 7 days earlier than the rootstock in June, and sowing the scion 5 days earlier than the rootstock from July to September; the grafting is suitable when the cotyledons of the rootstock and the scion are flat and just reveal the true leaves; removing the growth point of the rootstock with a grafting knife, and cutting downward at an angle of 20°-30° from the growth point, with a blade length of 0.5-1cm; cutting downward at an angle of 25°-30° at 0.8-1cm below the cotyledons of the scion, with a blade length of 0.5-0.6cm; fitting the incision of the scion with the incision of the stem of the rootstock, making the two tightly combined, and then fixing them with a grafting clamp.

9. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature seasons according to claim 1, characterized in that: The scion cultivation includes: a scion seedling raising period of 5-10 days before grafting, and temperature difference between day and night; when the light intensity exceeds 30,000 Lux, shading and cooling are achieved by building a small arch shed, and a shading net with a shading rate of >70% is used.

10. The method for raising seedlings for improving the survival rate of watermelon grafting in high temperature seasons according to claim 9, characterized in that: In the day and night temperature difference treatment, the day temperature in summer is 26-30°C and the night temperature is 16-20°C.

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