Breeding method of muskmelon with thick skin

Abstract

The invention provides a thick-skin muskmelon breeding method which comprises the following steps: S1, after accelerating germination of parent seeds, transplanting the parent seeds to a glass greenhouse seedling raising tray for seedling raising, covering a reflective mulching film after field planting, and regulating and controlling temperature, humidity, illumination and carbon dioxide concentration; s2, after field planting, picking male flowers on the blooming day for later use, bagging female flowers, then pollinating, and pollinating by adopting a mode of combining painting of pollen by a writing brush and spraying of male flower homogenate to ovaries; s3, after petals of female flowers wither, spraying a composite hormone solution and carrying out drip irrigation of a humic acid solution, and after fruit setting, implementing directional root zone irrigation and leaf nutrition regulation; and S4, screening fruits and taking seeds by using a near-infrared spectrometer, soaking the seeds in a chitosan oligosaccharide solution, absorbing moisture on the surfaces of the seeds, and drying in the shade to obtain target seeds for breeding. According to the breeding method, the number and quality of the hybrid seeds of the muskmelon can be effectively improved, and an efficient and reliable technical scheme is provided for variety breeding of the muskmelon.

Description

Technical Field

[0001] This invention relates to the field of breeding technology, specifically to a breeding method for thick-skinned melons. Background Technology

[0002] Muskmelon, belonging to the Cucurbitaceae family, is an annual vine-like herbaceous plant, also known as cantaloupe, fruit melon, etc. It boasts abundant varieties and diverse cultivation methods in my country. Based on ecological characteristics, muskmelons in my country are often divided into two categories: thick-skinned and thin-skinned. Thick-skinned muskmelons typically have larger fruits, finer flesh, higher sugar content, and better storage and transportation qualities, making them an important cultivated crop. With the development of protected agriculture, the cultivation area of ​​thick-skinned muskmelons is constantly expanding, and the demand for high-quality varieties is becoming increasingly urgent, making their breeding a crucial direction in agricultural research.

[0003] Currently, the breeding process for thick-skinned melons mainly includes defining breeding objectives, selecting breeding materials, identifying and evaluating innovative germplasm resources, configuring new variety combinations, selecting offspring, and conducting field trials. In traditional breeding processes, hybridization and pollination are crucial steps, typically involving emasculation, bagging, and pollen collection. However, existing breeding methods often face the problem of difficulty in obtaining seeds from hybridized or self-pollinated fruits, or the seeds being underdeveloped. This results in poor quality breeding materials, severely impacting seedling growth and the efficiency of subsequent variety selection.

[0004] The poor breeding quality in existing technologies is mainly due to insufficient pollination quality and inadequate nutrient supply for fruit development. On the one hand, pollen germination and pollen tube growth during pollination are significantly affected by environmental factors (such as temperature and humidity), which are difficult to precisely control using conventional cultivation methods, leading to poor fertilization and consequently insufficient seed quantity or reduced seed purity, thus affecting the breeding process. On the other hand, unreasonable nutrient allocation within the plant, with excess growth points consuming large amounts of nutrients, results in insufficient nutrition for fruit and seed development, leading to a low seed quantity and low seed plumpness. Therefore, existing breeding methods suffer from problems of insufficient seed quantity and poor seed quality. Summary of the Invention

[0005] In view of this, the present invention proposes a breeding method for thick-skinned melons to solve the above problems.

[0006] The technical solution of this invention is implemented as follows:

[0007] A breeding method for thick-skinned melons includes the following steps:

[0008] S1. Germinate the parent seeds. Once the radicle breaks through the seed coat, transplant them into seedling trays in a glass greenhouse. During the seedling stage, maintain the daytime temperature at 28-32℃ and the nighttime temperature at 16-18℃, with an air humidity of 65%-75% and a daily light exposure of no less than 12 hours. Transplant the seedlings after 30-33 days. After transplanting, cover the ridges with reflective mulch and maintain the soil temperature at 22-25℃, the air humidity at 60-70%, and the carbon dioxide fertilizer concentration at 800-1000 ppm.

[0009] S2. 30-33 days after transplanting, before the female flowers open, pick the male flowers on the day they bloom and set them aside. Separate the female flowers by covering them with bags. On the 3rd day after the female flowers open, remove the bags and pollinate them. First, take the male flowers and use a brush to evenly apply the pollen to the stigma of the female flowers. Then, spray the male flower paste onto the surface of the ovary 3-5 times.

[0010] S3. 48 hours after the female flower petals wither, spray with a compound hormone solution, which includes brassinolide, fungal secretions, kinetin, nano titanium dioxide and water, and drip irrigate with a 100 mg / L humic acid solution at the same time; 10-15 days after the female flowers on the 5th-7th nodes of the lateral vines set fruit, implement "targeted root zone irrigation" and carry out foliar nutrition regulation at the same time.

[0011] S4. After fruit set for 45-55 days, use a near-infrared spectrometer to screen fruits with a seed fullness of ≥85%. After breaking the fruit and extracting the seeds, soak them in a 0.8-1.5% chitosan oligosaccharide solution for 60-90 minutes. Then, take out the seeds, wipe the surface moisture with gauze or absorbent paper, and place them in a ventilated and cool place to air dry to obtain the breeding target seed.

[0012] Furthermore, the seedling substrate in the seedling tray described in S1 includes: 3-5 parts peat moss, 0.5-1 part vermiculite, 0.5-1 part perlite, 2-3 parts well-rotted manure, and 0.1-0.3 parts potassium phosphate.

[0013] Furthermore, the preparation method of the male flower homogenate described in S2 is as follows: take 100g of harvested male flowers, add 1000-1200mL of deionized water and 0.02-0.04g of cellulase, enzymatically hydrolyze at a constant temperature of 35-40℃ for 30-60min, and filter through a 200-mesh filter to obtain the male flower homogenate.

[0014] Furthermore, the male flower homogenate should be used within 1-2 hours after preparation, and the ambient temperature should be controlled at 22-25℃ during spraying. The cellulase activity should be ≥5000 IU.

[0015] Furthermore, the formulation of the compound hormone solution described in S2 is as follows: 2-5 parts brassinolide, 0.2-0.5 parts nano titanium dioxide, 2-3 parts fungal secretions, 0.5-1 parts kinetin, and 160-220 parts water.

[0016] Furthermore, the fungal secretions were prepared by the following method: *Glomus radicans* was selected as the inoculum. A 5mm diameter mycelial cake was cut using a sterile punch and inoculated into an agar medium containing 0.8% agar and 0.01% yeast extract at pH 5.8-6.2. The culture was statically incubated at 24-26℃ in the dark for 7 days. Newly formed hyphae at the colony edge were cut, spores and browned hyphae were removed, and the culture was transferred to 1 / 2 MS liquid medium at pH 6.0-6.5 and incubated at 23-25℃ in the dark. The culture was incubated with shaking at 100-150 rpm for 14-16 days. The culture broth was collected and vacuum filtered through a 0.22 μm microporous membrane to remove mycelia. Three volumes of pre-cooled acetone were added to the filtrate and the mixture was precipitated at 3-5 °C for 10-15 h. The precipitate was then collected by centrifugation at 8000-10000 rpm for 10-20 min. The precipitate was dissolved in ultrapure water and then concentrated using a 10 kDa ultrafiltration membrane. The retained fraction was dialyzed to desalt and then freeze-dried to obtain fungal secretions.

[0017] Furthermore, the preparation method of the compound hormone solution described in S2 is as follows: brassinolide, nano titanium dioxide, fungal secretions, kinetin, and water are mixed and then ultrasonically dispersed. The ultrasonic dispersion frequency is 30-40kHz, the power is 180-200W, and the processing time is 10-15min.

[0018] Furthermore, the application rate of the compound hormone solution in S3 is 5-10 mL per young melon plant, and the application rate of the humic acid solution is 8-12 L per acre for drip irrigation. "Targeted root zone irrigation" is implemented by maintaining soil moisture content of 70-75% in the fruit-bearing lateral vine area and 55-60% in the non-fruit-bearing lateral vine area. Foliar nutrition regulation is carried out by spraying fruit-bearing vines with a solution of 25-35 ppm potassium dihydrogen phosphate + 4-6 ppm borax every 3 days, and non-fruit-bearing lateral vines with a solution of 80-120 ppm chlormequat chloride + 0.3-0.5% calcium chloride once a week.

[0019] Furthermore, S4 is air-dried until the moisture content is ≤8%.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This application creates a stable and suitable microenvironment for plant growth through precise control of parameters such as temperature, light, humidity, and gas composition. Based on the principles of plant physiology, suitable temperature can significantly increase the activity of seed germination enzymes and promote radicle growth; sufficient light duration and carbon dioxide concentration can enhance photosynthetic efficiency, providing sufficient energy and material basis for plant growth. This environment effectively improves the root development index of seedlings, and morphological indicators such as stem diameter and leaf area are significantly better than those of conventional seedling cultivation, laying a solid foundation for subsequent growth and development and effectively improving the initial quality of breeding materials.

[0022] 2. This application combines traditional manual pollination with male flower homogenization spraying in the pollination process. This composite pollination method can effectively improve the germination rate of the stigma, effectively overcome the adverse effects of environmental factors on the pollination process, significantly improve the fertilization success rate, and provide a guarantee for the formation of high-quality seeds.

[0023] 3. The method of this application utilizes a compound hormone solution where brassinolide enhances plant stress resistance by regulating cell membrane permeability and enzyme activity; fungal secretions promote synchronized embryo sac development, increasing seed plumpness; kinetin delays leaf senescence, maintaining a continuous supply of photosynthetic products; and nano-titanium dioxide improves the plant's efficiency in utilizing light energy. The synergistic effect of brassinolide, fungal secretions, kinetin, and nano-titanium dioxide effectively promotes seed development while avoiding the influence of excessively high or low concentrations of any single component, precisely regulating the physiological and biochemical reactions during seed development, thereby improving seed quality. Detailed Implementation

[0024] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0025] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0026] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0027] Example 1

[0028] A breeding method for thick-skinned melons includes the following steps:

[0029] S1. Germinate the parent seeds. Once the radicle breaks through the seed coat, transplant them into seedling trays in a glass greenhouse. During the seedling stage, maintain a daytime temperature of 28℃, a nighttime temperature of 16℃, an air humidity of 65%, and 12 hours of light per day. Transplant the seedlings after 33 days. After transplanting, cover the raised beds with reflective mulch and maintain a soil temperature of 22℃, an air humidity of 600%, and a carbon dioxide concentration of 800 ppm. The seedling substrate in the trays includes: 3 parts peat moss, 0.5 parts vermiculite, 0.5 parts perlite, 2 parts well-rotted manure, and 0.1 parts potassium phosphate.

[0030] S2. Thirty days after transplanting, before the female flowers open, pick the male flowers that bloom on the same day and set them aside. Separate the female flowers by covering them with bags. On the third day after the female flowers open, remove the bags for pollination. First, take the pollen from the male flowers and use a brush to evenly apply the pollen to the stigma of the female flowers. Then, spray the male flower paste onto the surface of the ovary three times.

[0031] The preparation method of the above-mentioned male flower homogenate is as follows: Take 100g of harvested male flowers, add 1000mL of deionized water and 0.02g of cellulase, enzymatically hydrolyze at a constant temperature of 35℃ for 300min, and filter through a 200-mesh filter to obtain male flower homogenate.

[0032] The male flower homogenate should be used within 1 hour after preparation. The ambient temperature should be controlled at 22℃ during spraying, and the cellulase activity should be 5000 IU.

[0033] The compound hormone solution is prepared as follows: 2 parts brassinolide, 0.2 parts nano titanium dioxide, 2 parts fungal secretions, 0.5 parts kinetin, and 160 parts water.

[0034] The fungal secretions were prepared by the following method: *Glomus radiata* was selected as the strain. A 5mm diameter mycelial cake was cut using a sterile punch and inoculated into an agar medium containing 0.8% agar and 0.01% yeast extract at pH 5.8. The culture was statically incubated at 24°C in the dark for 7 days. Newly formed hyphae at the colony edge were cut, spores and browned hyphae were removed, and the culture was transferred to 1 / 2 MS liquid medium at pH 6.0 and cultured at 23°C in the dark with shaking at 100 rpm for 16 days. The culture broth was collected and vacuum filtered through a 0.22μm microporous membrane to remove mycelia. Three volumes of pre-cooled acetone were added to the filtrate, and precipitation was carried out at 3°C ​​for 15 hours. The precipitate was then collected by centrifugation at 8000 rpm for 20 minutes. The precipitate was dissolved in ultrapure water, and then concentrated using a 10kDa ultrafiltration membrane. The retained fraction was dialyzed to remove salts and then freeze-dried to obtain the fungal secretions.

[0035] The preparation method of the compound hormone solution is as follows: brassinolide, nano-titanium dioxide, fungal secretions, kinetin, and water are mixed and then ultrasonically dispersed. The ultrasonic dispersion frequency is 30kHz, the power is 180W, and the treatment time is 15min.

[0036] S3. 48 hours after the female flower petals wither, spray with a compound hormone solution, which includes brassinolide, fungal secretions, kinetin, nano-titanium dioxide, and water. Spray 5 mL per young melon plant, and simultaneously drip irrigate with a 100 mg / L humic acid solution, 8 L per acre. 10 days after the female flower sets fruit on the 5th node of the lateral vine, implement "targeted root zone irrigation," specifically maintaining a soil moisture content of 70% in the fruit-bearing lateral vine area and 55% in the non-fruit-bearing lateral vine area. At the same time, perform foliar nutrition regulation, specifically spraying the fruit-bearing vine with a 25 ppm potassium dihydrogen phosphate + 4 ppm borax solution every 3 days, and spraying the non-fruit-bearing lateral vine with an 80 ppm chlormequat chloride + 0.3% calcium chloride solution once a week.

[0037] S4. 45 days after fruit set, fruits with a seed fullness of 85% were screened using a near-infrared spectrometer. After breaking the fruit and extracting the seeds, they were soaked in a 0.8% chitosan oligosaccharide solution for 90 minutes. Then, the seeds were taken out and the surface moisture was absorbed by gauze or absorbent paper. They were then placed in a ventilated and shady place to air dry until the moisture content was 8%, thus obtaining the target breeding variety.

[0038] Example 2

[0039] A breeding method for thick-skinned melons includes the following steps:

[0040] S1. Germinate the parent seeds. Once the radicle breaks through the seed coat, transplant them into seedling trays in a glass greenhouse. During the seedling stage, maintain a daytime temperature of 30℃, a nighttime temperature of 17℃, an air humidity of 70%, and a daily light duration of 13 hours. Transplant the seedlings after 32 days. After transplanting, cover the raised beds with reflective mulch and maintain a soil temperature of 23.5℃, an air humidity of 65%, and a carbon dioxide fertilizer concentration of 900 ppm. The seedling substrate in the seedling trays includes: 4 parts peat moss, 0.8 parts vermiculite, 0.8 parts perlite, 2.5 parts well-rotted manure, and 0.2 parts potassium phosphate.

[0041] S2. 32 days after transplanting, before the female flowers open, pick the male flowers that bloom on the same day and set them aside. Separate the female flowers by covering them with bags. On the third day after the female flowers open, remove the bags for pollination. First, take the pollen from the male flowers and use a brush to evenly apply the pollen to the stigma of the female flowers. Then, spray the male flower paste onto the surface of the ovary four times.

[0042] The preparation method of the above-mentioned male flower homogenate is as follows: Take 100g of harvested male flowers, add 1100mL of deionized water and 0.03g of cellulase, enzymatically hydrolyze at a constant temperature of 37.5℃ for 45min, and filter through a 200-mesh filter to obtain male flower homogenate.

[0043] The male flower homogenate should be used within 1.5 hours after preparation. The ambient temperature should be controlled at 23.5℃ during spraying, and the cellulase activity should be 6000 IU.

[0044] The compound hormone solution is prepared as follows: 3.5 parts brassinolide, 0.4 parts nano titanium dioxide, 2.5 parts fungal secretions, 0.8 parts kinetin, and 190 parts water.

[0045] The fungal secretions were prepared by the following method: *Glomus radiata* was selected as the strain. A 5mm diameter mycelial cake was cut using a sterile punch and inoculated into an agar medium containing 0.8% agar and 0.01% yeast extract at pH 6.0. The culture was statically incubated at 25°C in the dark for 7 days. Newly formed hyphae at the colony edge were cut, spores and browned hyphae were removed, and the culture was transferred to 1 / 2 MS liquid medium at pH 6.2 and cultured at 24°C in the dark with shaking at 120 rpm for 15 days. The culture broth was collected and vacuum filtered through a 0.22μm microporous membrane to remove mycelia. Three volumes of pre-cooled acetone were added to the filtrate, and precipitation was carried out at 4°C for 12.5 hours. The precipitate was then collected by centrifugation at 9000 rpm for 15 minutes. The precipitate was dissolved in ultrapure water, and the retained fraction was concentrated using a 10kDa ultrafiltration membrane. The retained fraction was dialyzed to remove salts and then freeze-dried to obtain the fungal secretions.

[0046] The preparation method of the compound hormone solution is as follows: brassinolide, nano-titanium dioxide, fungal secretions, kinetin, and water are mixed and then ultrasonically dispersed. The ultrasonic dispersion frequency is 35 kHz, the power is 190 W, and the treatment time is 12.5 min.

[0047] S3. 48 hours after the female flower petals wither, spray with a compound hormone solution, which includes brassinolide, fungal secretions, kinetin, nano-titanium dioxide, and water. Spray 7.5 mL per young melon plant, and simultaneously drip irrigate with a 100 mg / L humic acid solution, 10 L per acre. 12 days after the female flower sets fruit on the 6th node of the lateral vine, implement "targeted root zone irrigation," specifically maintaining a soil moisture content of 72% in the fruit-bearing lateral vine area and 58% in the non-fruit-bearing lateral vine area. At the same time, perform foliar nutrition regulation, specifically spraying the fruit-bearing vine with a 30 ppm potassium dihydrogen phosphate + 5 ppm borax solution every 3 days, and spraying the non-fruit-bearing lateral vine with a 100 ppm chlormequat chloride + 0.4% calcium chloride solution once a week.

[0048] S4. Fifty days after fruit set, fruits with a seed fullness of 85% were screened using a near-infrared spectrometer. After breaking open the fruit and extracting the seeds, they were soaked in a 1.2% chitosan oligosaccharide solution for 75 minutes. Then, the seeds were taken out and the surface moisture was absorbed with gauze or absorbent paper. They were then placed in a ventilated and shady place to air dry until the moisture content was 7%, thus obtaining the target breeding variety.

[0049] Example 3

[0050] A breeding method for thick-skinned melons includes the following steps:

[0051] S1. Germinate the parent seeds. Once the radicle breaks through the seed coat, transplant them into seedling trays in a glass greenhouse. During the seedling stage, maintain a daytime temperature of 32℃, a nighttime temperature of 18℃, an air humidity of 75%, and 14 hours of light per day. Transplant the seedlings after 30 days. After transplanting, cover the raised beds with reflective mulch and maintain a soil temperature of 25℃, an air humidity of 70%, and a carbon dioxide fertilizer concentration of 1000ppm. The seedling substrate in the seedling trays includes: 5 parts peat moss, 1 part vermiculite, 1 part perlite, 3 parts well-rotted manure, and 0.3 parts potassium phosphate.

[0052] S2. 33 days after transplanting, before the female flowers open, pick the male flowers that bloom on the same day and set them aside. Separate the female flowers by covering them with bags. On the third day after the female flowers open, remove the bags for pollination. First, take the male flowers and use a brush to evenly apply the pollen to the stigma of the female flowers. Then, spray the male flower paste onto the surface of the ovary five times.

[0053] The preparation method of the above-mentioned male flower homogenate is as follows: take 100g of picked male flowers, add 1200mL of deionized water and 0.04g of cellulase, enzymatically hydrolyze at a constant temperature of 40℃ for 30min, and filter through a 200-mesh filter to obtain male flower homogenate.

[0054] The male flower homogenate should be used within 2 hours of preparation. The ambient temperature should be controlled at 25℃ during spraying, and the cellulase activity should be 7000 IU.

[0055] The compound hormone solution is prepared as follows: 5 parts brassinolide, 0.5 parts nano titanium dioxide, 3 parts fungal secretions, 1 part kinetin, and 220 parts water.

[0056] The fungal secretions were prepared by the following method: *Glomus radiata* was selected as the strain. A 5mm diameter mycelial cake was cut using a sterile punch and inoculated into an agar medium containing 0.8% agar and 0.01% yeast extract at pH 6.2. The culture was statically incubated at 26°C in the dark for 7 days. Newly formed hyphae at the colony edge were cut, spores and browned hyphae were removed, and the culture was transferred to 1 / 2 MS liquid medium at pH 6.5 and cultured at 25°C in the dark with shaking at 150 rpm for 16 days. The culture broth was collected and vacuum filtered through a 0.22μm microporous membrane to remove mycelia. Three volumes of pre-cooled acetone were added to the filtrate, and precipitation was carried out at 5°C for 10 hours. The precipitate was then collected by centrifugation at 10,000 rpm for 10 minutes. The precipitate was dissolved in ultrapure water, and then concentrated using a 10kDa ultrafiltration membrane. The retained fraction was dialyzed to remove salts and then freeze-dried to obtain the fungal secretions.

[0057] The preparation method of the compound hormone solution is as follows: brassinolide, nano-titanium dioxide, fungal secretions, kinetin, and water are mixed and then ultrasonically dispersed at a frequency of 40 kHz, a power of 200 W, and a treatment time of 10 min.

[0058] S3. 48 hours after the female flower petals wither, spray with a compound hormone solution, which includes brassinolide, fungal secretions, kinetin, nano-titanium dioxide, and water. Spray 10 mL per young melon plant, and simultaneously drip irrigate with a 100 mg / L humic acid solution, at a rate of 12 L per acre. 15 days after the female flower sets fruit on the 7th node of the lateral vine, implement "targeted root zone irrigation," specifically maintaining a soil moisture content of 75% in the fruit-bearing lateral vine area and 60% in the non-fruit-bearing lateral vine area. At the same time, perform foliar nutrition regulation, specifically spraying the fruit-bearing vine with a 35 ppm potassium dihydrogen phosphate + 6 ppm borax solution every 3 days, and spraying the non-fruit-bearing lateral vine with a 120 ppm chlormequat chloride + 0.5% calcium chloride solution once a week.

[0059] S4. After 55 days of fruit set, fruits with a seed fullness of 85% were screened using a near-infrared spectrometer. After breaking the fruit and extracting the seeds, they were soaked in a 1.5% chitosan oligosaccharide solution for 60 minutes. Then, the seeds were taken out and the surface moisture was absorbed with gauze or absorbent paper. They were then placed in a ventilated and shady place to air dry until the moisture content was 6%, thus obtaining the target breeding variety.

[0060] Comparative Example 1

[0061] Compared with Example 2, the difference in this comparative example is that in step S2, only the pollen of the male flower is evenly applied to the stigma of the female flower with a brush, and the male flower homogenate is no longer sprayed.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that the compound hormone solution is not sprayed in step S3.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 2 is that the compound hormone solution does not contain fungal secretions.

[0066] Test subjects: Seeds obtained from Examples 1-3 and Comparative Examples 1-3.

[0067] Test items:

[0068] 1. Number of seeds per fruit

[0069] Mature fruits from each embodiment and comparative example were randomly selected. Ten fruits were selected from each treatment group. The fruits were cut open, all seeds were collected, the number of seeds in each fruit was counted, and the average value was recorded and calculated (the result was rounded to the nearest integer).

[0070] 2. Seed germination rate

[0071] One hundred seeds were randomly selected from each of the seeds cultivated in Examples 1-3 and Comparative Examples 1-3. Five groups of seeds were set up for each example and comparative example. The seeds were placed in petri dishes lined with moistened filter paper and placed in a constant temperature incubator (25℃, light 12h / d). On the 7th day, the number of germinated seeds was counted (based on the radicle breaking through the seed coat ≥2mm), and the germination rate was calculated. The average value of the five groups was taken.

[0072] 3. Fruit setting rate

[0073] Seeds that germinated in the germination test were transplanted into seedling trays and cultivated under standard conditions until they reached seedling stage (2-3 true leaves). The seedlings were then transplanted to the field or greenhouse and planted according to standardized cultivation and management practices. The number of ovules was counted during the flowering period. After the plants matured, the number of seeds produced per plant was counted, and the seed set rate per plant was calculated and averaged.

[0074] Test results: See Table 1.

[0075] Table 1

[0076] Average number of seeds per fruit Germination rate (%) Fruit setting rate (%) Example 1 597 94.7 90.3 Example 2 607 95.6 91.3 Example 3 601 96.1 90.2 Comparative Example 1 432 78.6 72.3 Comparative Example 2 448 80.2 74.8 Comparative Example 3 563 88.5 83.2

[0077] As shown in Table 1, the average number of seeds per fruit in Examples 1-3 was 197-207, significantly higher than that in Comparative Examples 1-3. This demonstrates that the breeding method of this application can yield a larger number of seeds, which is beneficial for improving the breeding efficiency of thick-skinned melons.

[0078] By comparing Comparative Example 1 and Example 2, this application combines traditional artificial pollination with male flower homogenate spraying in the pollination stage. This composite pollination method effectively improves the germination rate of the stigma, effectively overcomes the adverse effects of environmental factors on the pollination process, significantly improves the fertilization success rate, and provides a guarantee for the formation of high-quality seeds. In this application, the pollen activity of male flowers on the day of flowering is high, and cellulase can decompose the cell wall, allowing the nutrients and active ingredients in the pollen to be fully released into the homogenate. The pollen-specific proteins, polysaccharides, and lipids in the homogenate provide a direct carbon and nitrogen source for ovary development. Zeatin nucleosides and gibberellins in the homogenate synergistically regulate ovule development. The cellobiose and oligosaccharide fragments produced during the enzymatic hydrolysis process act as elicitors, stimulating the ovary epidermal cells to synthesize chitinase and β-1,3-glucanase, clearing potential pathogens, thereby reducing the abortion rate, reducing breeding defects, and improving breeding quality. Furthermore, amino acids in the homogenate enter the ovule via plasma membrane transporters, promoting embryo sac cell division, increasing the number of seeds per melon, and improving seed quality. Seed quality directly affects embryo vigor, nutrient reserves, and stress resistance. High-quality seeds have intact embryo structures, strong cell division activity, and can quickly break through the seed coat during germination, resulting in seedlings with well-developed root systems, high photosynthetic efficiency, sufficient early nutrient accumulation, and more complete flower bud differentiation. Therefore, high-quality seeds have a significant impact on germination rate and seed setting rate.

[0079] Comparing Comparative Example 2 with Example 2, the brassinolide in the compound hormone solution of this application activates cell wall relaxation-related gene expression by activating plasma membrane-localized receptor kinases, promoting the expansion of ovule integument cells and increasing the number of seeds per melon. The lipid chitosan oligosaccharides and strigolactones contained in fungal secretions activate ovary cell signaling pathways, promoting synchronized embryo sac development and improving seed plumpness. Chitinase and β-1,3-glucanase contained in fungal secretions induce local immunity in the ovary, enhancing resistance to gray mold and increasing seed setting rate. Kinetin delays ovule integument cell senescence, reducing the abortion rate. Kinetin can also upregulate glutamine synthase activity, promoting nitrogen assimilation and providing sufficient amino acids for seed development. Nano-titanium dioxide generates reactive oxygen species under light, inhibiting pathogens on the ovary surface and reducing fruit drop rate. Brassinolide and kinetin form a synergistic "expansion-division" effect. Brassinolide promotes cell expansion, providing space for kinetin-induced division and increasing ovule volume. The compound hormone solution systematically improves breeding quality through a triple mechanism of "hormonal regulation-stress enhancement-nutrient synergy," providing an efficient technical solution for thick-skinned melon breeding.

[0080] By comparing Comparative Example 3 with Example 3, it can be seen that fungal secretions are an important component of the compound hormone solution. The lack of fungal secretions will lead to a decrease in seed quality, thereby reducing the germination rate and seed setting rate.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A breeding method for thick-skinned melons, characterized in that, Includes the following steps: S1. Germinate the parent seeds. Once the radicle breaks through the seed coat, transplant them into seedling trays in a glass greenhouse. During the seedling stage, maintain the daytime temperature at 28-32℃ and the nighttime temperature at 16-18℃, with an air humidity of 65-75% and a daily light exposure of no less than 12 hours. Transplant the seedlings after 30-33 days. After transplanting, cover the ridges with reflective mulch and maintain the soil temperature at 22-25℃, the air humidity at 60-70%, and the carbon dioxide fertilizer concentration at 800-1000 ppm. S2. 30-33 days after transplanting, pick the male flowers on the day of flowering before the female flowers open, and set them aside. Separate the female flowers by covering them with bags. On the 3rd day after the female flowers open, remove the bags for pollination. First, take the male flowers and use a brush to evenly apply the pollen to the stigma of the female flowers. Then, spray the male flower paste onto the surface of the ovary 3-5 times. S3. 48 hours after the female flower petals wither, spray with a compound hormone solution, which includes brassinolide, fungal secretions, kinetin, nano titanium dioxide and water, and drip irrigate with a 100 mg / L humic acid solution at the same time; 10-15 days after the female flowers on the 5th-7th nodes of the lateral vines set fruit, implement "targeted root zone irrigation" and carry out foliar nutrition regulation at the same time. S4. After fruit set for 45-55 days, use a near-infrared spectrometer to screen fruits with a seed fullness of ≥85%. After breaking the fruit and extracting the seeds, soak them in a 0.8-1.5% chitosan oligosaccharide solution for 60-90 minutes. Then, take out the seeds, wipe the surface moisture with gauze or absorbent paper, and place them in a ventilated and cool place to air dry to obtain the breeding target seed.

2. The breeding method for thick-skinned melons as described in claim 1, characterized in that, The seedling substrate in the seedling tray described in S1 includes: 3-5 parts peat moss, 0.5-1 part vermiculite, 0.5-1 part perlite, 2-3 parts well-rotted manure, and 0.1-0.3 parts potassium phosphate.

3. The breeding method for thick-skinned melons as described in claim 1, characterized in that, The preparation method of male flower homogenate described in S2 is as follows: Take 100g of harvested male flowers, add 1000-1200mL of deionized water and 0.02-0.04g of cellulase, and enzymatically hydrolyze at a constant temperature of 35-40℃ for 30-60min. Filter through a 200-mesh filter to obtain male flower homogenate.

4. The breeding method for thick-skinned melons as described in claim 3, characterized in that, The male flower homogenate should be used within 1-2 hours after preparation. The ambient temperature should be controlled at 22-25℃ during spraying. The cellulase activity should be ≥5000 IU.

5. The breeding method for thick-skinned melons as described in claim 1, characterized in that, The compound hormone solution described in S2 is prepared as follows: 2-5 parts brassinolide, 0.2-0.5 parts nano titanium dioxide, 2-3 parts fungal secretions, 0.5-1 part kinetin, and 160-220 parts water.

6. The breeding method for a thick-skinned melon as described in claim 6, characterized in that, The fungal secretions were prepared by the following method: *Gastrodia elata* was selected as the strain. A 5mm diameter mycelial cake was cut using a sterile punch and inoculated into an agar medium containing 0.8% agar and 0.01% yeast extract at pH 5.8-6.

2. The culture was incubated statically at 24-26℃ in the dark for 7 days. Newly formed hyphae at the colony edge were cut, spores and browned hyphae were removed, and the culture was transferred to 1 / 2 MS liquid medium at pH 6.0-6.5 and incubated at 23-25℃ in the dark. The culture was shaken at 100-150 rpm for 14-16 days. The culture broth was collected and vacuum filtered through a 0.22 μm microporous membrane to remove mycelia. Three volumes of pre-cooled acetone were added to the filtrate and the mixture was precipitated at 3-5℃ for 10-15 h. The precipitate was then collected by centrifugation at 8000-10000 rpm for 10-20 min. The precipitate was dissolved in ultrapure water and then concentrated using a 10 kDa ultrafiltration membrane. The retained fraction was dialyzed to desalt and then freeze-dried to obtain fungal secretions.

7. The breeding method for thick-skinned melons as described in claim 1, characterized in that, The preparation method of the compound hormone solution described in S2 is as follows: Brassinolide, nano titanium dioxide, fungal secretions, kinetin, and water are mixed and then ultrasonically dispersed. The ultrasonic dispersion frequency is 30-40kHz, the power is 180-200W, and the processing time is 10-15min.

8. The breeding method for a thick-skinned melon as described in claim 1, characterized in that, The application rate of the compound hormone solution in S3 is 5-10 mL per young melon plant, and the application rate of the humic acid solution is 8-12 L per acre for drip irrigation. The "targeted root zone irrigation" is implemented by maintaining the soil moisture content at 70-75% in the fruit-bearing lateral vine area and 55-60% in the non-fruit-bearing lateral vine area. Foliar nutrition regulation is implemented by spraying the fruit-bearing vine with a solution of 25-35 ppm potassium dihydrogen phosphate + 4-6 ppm borax every 3 days, and spraying the non-fruit-bearing lateral vine with a solution of 80-120 ppm chlormequat chloride + 0.3-0.5% calcium chloride once a week.

9. The breeding method for a thick-skinned melon as described in claim 1, characterized in that, The S4 is air-dried until the moisture content is ≤8%.