A method for hybrid seed production by using celery male sterility QCBU-001

Abstract

The application discloses a method for hybrid seed production by using celery male sterility QCBU-001, and belongs to the technical field of plant hybrid seed production. The method takes the celery male sterility material QCBU-001 as the female parent, and takes the fertile celery variety as the male parent, and comprises the following steps: sowing and raising seedlings at the end of October, not covering soil, and giving water at the bottom; transplanting to 72-hole hole trays at the 3-leaf stage and cultivating to the 5-leaf stage; planting according to 4 rows of female parents and 1 row of male parents, with a plant spacing of 0.6 m, a row spacing of the female parents of 0.5 m, and a row spacing of the male parents of 0.5 m; the female parents naturally bloom, and the male parents bloom by means of picking main canes or spraying gibberellin; the male parents are cut off at the node of the fifth level inflorescence pollination end and seed swelling; and the seeds are collected when the fifth level inflorescence seeds turn yellow. The application effectively improves hybrid seed production yield, guarantees seed purity and germination uniformity, and reduces seed production cost.

Description

Technical Field

[0001] This invention relates to the field of plant hybridization seed production technology, and in particular to a method for hybridization seed production using celery male-sterile QCBU-001. Background Technology

[0002] celery( Apium graveolens Celery (L.) is a biennial vegetable crop belonging to the genus *Apis* of the family Apiaceae. In my country, its annual cultivation area is stable at 550,000 hectares, with a yield of approximately 20 million tons, making it an important leafy vegetable. However, celery has a unique floral structure: the flowers are bisexual, and the florets are generally less than 2 mm in diameter. The compound umbels are indeterminate, and there is significant inconsistency in the differentiation and opening time of each secondary inflorescence and floret. The flowering period of a single plant can last for 20-30 days. Simultaneously, the thousand-seed weight is only 0.4-0.6 g, the hypocotyl is short, and seedling growth is weak. These biological characteristics make artificial emasculation and hybridization extremely difficult, resulting in a low success rate of emasculation of individual flowers and very low seed production, severely restricting the breeding and large-scale seed production of celery hybrids. Therefore, obtaining a stable genetic male-sterile line and establishing a supporting high-efficiency seed production technology are key prerequisites for overcoming the bottlenecks in the industrial application of celery hybrids.

[0003] Currently, four cases of male-sterile celery materials have been reported both domestically and internationally. The male-sterile materials discovered by Quiros et al. are unstable in fertility, making it difficult to guarantee the complete sterility rate of sterile plants in the seed production population. This easily leads to the introduction of self-pollinated plants into the offspring, directly affecting the purity and commercial consistency of the hybrid (Quiros CF, et al. Cytological and genetical studies of amale sterile celery. Euphytica, 1986, 35(3): 867-875). The 01-3A line reported by Jin Lizheng et al. is a recessive nuclear male-sterile dual-purpose line, with fertile and sterile plants each accounting for half of its population (Jin Lizheng, et al. Key points of hybrid seed production technology for male-sterile dual-purpose celery lines. Northern Horticulture, 2011, 8: 62), during seed production, approximately 50% of fertile plants must be manually removed. Due to the lack of reliable morphological markers during the seedling and vegetative growth stages of celery, current techniques only allow for individual plant inspection at the early flowering stage. This operation is not only inefficient and costly, but the removal process also easily damages the tender inflorescences of adjacent sterile plants, leading to a reduction in effective fruiting inflorescences and ultimately lowering the yield of hybrid seeds per unit area. Cheng et al. reported the screening of a mitochondrial male-sterile celery material, W99A, from the celery resource *tanzhixiangqin* (Cheng Q, et al. Complete mitochondrial genome sequence and identification of a candidate gene responsible for cytoplasmic male sterility in celery). Apium graveolens L.). International Journal of Molecular Sciences, 2021, 22(16): e8584); The inventors' team used radiation mutagenesis to screen celery male sterility QCBU-001 (Tan Guofei, et al. Creation of celery male sterility and identification of mitochondrial sterility candidate genes. Journal of Plant Genetic Resources, 2022, 23(6): 1807-1815.). Existing studies have focused on the localization of sterility genes and the analysis of physiological mechanisms, and no systematic technical solutions have been found for key parameters such as the amount of male pollen supply, the number of pollinations and the timing of pollination in its large-scale seed production. Furthermore, none of the reported materials address the corresponding seed production techniques for the asynchronous development of celery indeterminate inflorescences. Traditional one or two pollination methods cannot cover the entire flowering period, resulting in empty and shriveled seeds from the ovules at the inflorescence apex and secondary branches failing to receive effective pollen. This not only leads to low seed production but also causes significant differences in seed plumpness and uneven germination among seeds harvested in the same batch, seriously affecting the quality grade of hybrid seeds as commercial seeds.

[0004] There are systemic technological gaps between the practical needs of celery hybrid seed production and existing technologies: Due to the lack of a fully quantified seed production procedure for specific male-sterile materials, in actual production, we can only rely on the extensive experience of conventional seed breeding or other umbelliferous crops. It is difficult to accurately determine the sowing time difference between the male-sterile line and the male parent to achieve a perfect flowering period. Often, due to insufficient pollen supply from the male parent or the misalignment of the supply window with the peak flowering period of the female parent, the problem of low seed setting rate is further aggravated. At the same time, there is a lack of overall planning between the timing of removing fertile plants and the pollination operation nodes. If the plants are removed in advance to ensure purity, the male-sterile plants may be damaged and the flowering density of the population may be reduced. If the removal is delayed to ensure pollination, the risk of pollen contamination will increase. This contradiction cannot be effectively resolved in the existing technology. The root cause of the above problems lies in the deep mismatch between the indeterminate inflorescence development characteristics of celery and traditional seed production agronomic practices. Solving these difficulties requires not only screening out completely sterile and stable materials, but also redesigning a complete set of technical parameters for these materials, including sowing schedule, planting density, flowering period control, quantitative indicators for assisted pollination, optimal removal point for fertile plants, and determination of the appropriate seed harvest period. Summary of the Invention

[0005] The purpose of this invention is to provide a method for seed production using celery male-sterile strain QCBU-001 hybridization, thereby solving the problems existing in the prior art. This invention addresses the difficulties in celery hybridization seed production by precisely setting the sowing date, optimizing the arrangement of parent plants in the field, and determining the timing of male parent removal and seed harvesting based on the fifth-order inflorescence. The yield per acre reaches over 300 catties, with a thousand-seed weight of 0.8–1.0 g and a germination rate of over 85%. It eliminates the need for manual emasculation and assisted pollination, effectively improving seed yield and quality while reducing seed production costs.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for seed production using celery male-sterile strain QCBU-001 hybridization, comprising the following steps: Sowing and seedling raising: At the end of October, the female seeds of male sterile celery QCBU-001 and the male seeds of fertile celery were sown in seedling trays respectively. After sowing, no soil was covered. Water was supplied by bottom watering. When the seedlings grew to the 3-leaf stage, they were transplanted into 72-cell seedling trays and continued to be cultivated until the 5-leaf stage. Field transplanting: After hardening off the seedlings at the 5-leaf stage, transplant them into the field with mulched ridges. Plant the female parent in 4 rows in the same ridge, and plant the male parent in 1 row. The spacing between female parent plants is 0.6m and the row spacing is 0.5m. The spacing between male parent plants is 0.6m. The distance between the male parent row and the adjacent female parent ridge is 0.5m. The arrangement is in a unit cycle of "female parent ridge - male parent row - female parent ridge". Flowering period control: The female parent flowers naturally. When the male parent flowers earlier than the female parent, remove the main stem of the male parent. When the male parent flowers later than the female parent, spray the male parent with gibberellin solution. Field pollination: Pollination is completed by natural wind and pollinating insects. When the fifth inflorescence of the female plant has finished pollination and the seeds begin to swell, all male plants in the field are cut off. Seed harvesting: When the seeds of the fifth inflorescence of the mother plant turn from green to yellow, the mother plant is cut off, dried, threshed, and the seeds are winnowed to obtain pure seeds. After drying until the moisture content is below 8%, the seeds are sealed and stored.

[0007] Optionally, the fertile male parent is selected from any one of 'Ningqin No. 1', 'Ningqin No. 2', 'Ventura', 'Huai'an medicinal celery', 'Guiyang small celery', 'Nanxuan Liuhe purple celery', or 'Chengdu white celery'.

[0008] Optionally, in the sowing and seedling raising step, the seedling tray has a length of 60cm, a width of 30cm, and a height of 3.3cm, and the bottom of the tray is provided with permeable holes.

[0009] Optionally, in the sowing and seedling raising process, 300 seeds are sown per tray, the moisture content of the nutrient soil is 70% to 80% of field capacity, and the substrate moisture content is maintained at 60% to 80% after germination.

[0010] Optionally, in the field planting process, the ridge height is 30 cm, and the ridge surface is covered with gray mulch. Before planting, the field fertility is tested. If the fertility is high, no fertilizer is applied. If the fertility is insufficient, 80 kg of decomposed organic fertilizer is applied per acre.

[0011] Optionally, in the field transplanting process, the seedling hardening time is 7 days, which is carried out by controlling water and ventilation.

[0012] Optionally, during the field planting process, the following pest and disease control measures can be implemented: for celery blight, use 45% chlorothalonil fumigant at a rate of 100-150 g per acre, applied every 9 days; for celery rust, use 50% carbendazim wettable powder at a rate of 60-120 g per acre; and for aphids, use 3% abamectin emulsifiable concentrate diluted 1000-2000 times and sprayed.

[0013] Optionally, in the flowering period control step, when the male parent flowers later than the female parent, the concentration of the gibberellin solution sprayed is 20-30 mg / L, and it is sprayed once at the early stage of bolting of the male parent.

[0014] Optionally, during the seed harvesting process, the seeds are dried for 3 to 5 days, sealed, and stored at room temperature (15 to 25°C) for 2 months.

[0015] The present invention also provides an application of the method in improving the yield, uniformity and quality of celery hybrid seed production.

[0016] The present invention discloses the following technical effects: This invention addresses the difficulties in hybrid seed production caused by the small flower size and asynchronous development of indeterminate inflorescences in celery. It provides a fully quantified method for hybrid seed production using the male-sterile celery variety QCBU-001. By precisely setting the sowing time to the end of October, combined with a seedling raising method of no soil covering and bottom watering, and a specific field arrangement of 4 rows of female parent and 1 row of male parent (plant spacing 0.6m, female parent row spacing 0.5m, male parent row spacing 0.5m), the method ensures suitable seedling age, sufficient vernalization, and effective pollen coverage from the source. This solves the problems of misaligned flowering time and insufficient pollination caused by missing sowing and planting parameters in existing technologies. Using this method, more than 300 catties of hybrid seeds can be obtained per mu (approximately 0.067 hectares), while the yield of traditional self-pollination or conventional seed production is only 100-200 catties, significantly increasing the yield of hybrid seed production.

[0017] This invention further addresses the inconsistent development of branches at each level in celery indeterminate inflorescences by establishing a paternal parent removal and seed harvesting node based on the fifth-level inflorescence. This avoids pollen contamination from the paternal parent and early seed loss due to shedding. Combined with natural pollination, targeted pest and disease control, and post-harvest winnowing and ripening treatment, the resulting hybrid seeds have a thousand-seed weight of 0.8–1.0 g, significantly superior to the conventional thousand-seed weight of 0.5–0.8 g for commercial seeds. The seeds exhibit good plumpness and high uniformity, with a germination rate exceeding 85% in germination tests, ensuring the quality grade of the hybrid seeds as commercial seeds. This invention eliminates the need for manual emasculation and artificial pollination throughout the entire process, significantly reducing labor costs in seed production and providing a reliable technical solution for the large-scale production of celery hybrids. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The fertile celery variety ‘Jinan Shiqin’ (A) and the male-sterile celery material QCBU-001 (B) were compared. Figure 2 This is a diagram showing the cyclical arrangement of planting units in the field; where triangles represent the female sterile material QCBU-001, and pentagrams represent the male fertile material. Figure 3 This is a diagram showing the effect of seed production in the field. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] Example 1. Material preparation and parent selection The maternal parent used in this embodiment is the celery male sterility material QCBU-001, which has been published in the literature "Tan Guofei, et al. Creation of celery male sterility and identification of mitochondrial sterility candidate genes. Journal of Plant Genetic Resources, 2022, 23(6): 1807-1815".

[0026] The anthers and filaments of the male-sterile celery material QCBU-001 are in a fleshy and degenerated state. Figure 1 The inability to form normal pollen and the sterility trait are caused by mitochondria. Cox1 Gene mutations lead to fertile materials Cox1 The gene length is 1497 bp (NCBI accession number: PZ548134.1), in the sterile material QCBU-001. Cox1 The gene length is 1641 bp (NCBI accession number: PZ548133.1). The sterility of the sterile material QCBU-001 is stable, and emasculation is not required in the seed production field. The male parent used in this example is the fertile celery variety 'Ningqin No. 1', which has normal flowering, high yield, wide adaptability, excellent quality, and high homozygosity, and has identifiable morphological differences from the female parent in agronomic traits such as plant type and leaf color. The male parent can also be selected from fertile varieties of the same type such as 'Ningqin No. 2', 'Ventura', 'Huai'an Medicinal Celery', 'Guiyang Small Celery', 'Nanxuan Liuhe Purple Celery', or 'Chengdu White Celery'. The applicant promises to release the above-mentioned female parent materials for 20 years from the date of application.

[0027] 2. Sowing and seedling raising In this embodiment, the parent seedlings were sown at the end of October. This timing was chosen based on the following considerations: Celery seeds are light-demanding, requiring sufficient light for germination, and the seedlings take approximately two months from sowing to reaching transplanting age. If sowing is too early, the seedlings will grow too large before winter, resulting in overly vigorous plants after bolting the following year, which is detrimental to field ventilation and light penetration, as well as seed production. If sowing is too late, the seedlings will not accumulate enough heat during the vernalization period, leading to delayed or absent bolting, affecting flowering timing. Therefore, sowing at the end of October ensures that the seedlings reach the appropriate age before the onset of winter temperatures, successfully completing vernalization while avoiding excessive plant growth.

[0028] Sowing is carried out using seedling trays and nutrient soil. The seedling trays are 60 cm long, 30 cm wide, and 3.3 cm high, with drainage holes at the bottom for both drainage and capillary absorption. Before sowing, commercial nutrient soil is filled into the seedling trays and moistened to 70%–80% of field capacity. Approximately 300 seeds are evenly sown in each tray. After sowing, the seeds are not covered with soil, allowing them to receive ample diffused light to promote germination. Watering after sowing should not be done by surface irrigation, as this can cause seed accumulation or excessive soil embedment, hindering germination. A bottom watering method should be used, placing the seedling trays in a shallow water trough. Water is then introduced from the bottom up through the drainage holes at the bottom of the tray, using capillary action to moisten the substrate, keeping the surface area around the seeds moist but not waterlogged.

[0029] After seed germination, maintain a well-ventilated and well-lit environment for seedling cultivation, keeping the substrate moisture between 60% and 80%. When the seedlings reach the 3-leaf stage, select healthy seedlings that are uniform in growth and free from pests and diseases, and transplant them into standard 72-cell seedling trays, one seedling per cell. After transplanting, continue cultivation in a greenhouse or plastic tunnel, maintaining suitable water, fertilizer, and light conditions to allow the seedlings to develop fully until they reach the 5-leaf stage for transplanting. The entire seedling stage lasts approximately 60 days. 3. Field planting When the celery seedlings reach the 5-leaf stage, hardening-off treatment is carried out for 7 days, enhancing the seedlings' resistance through measures such as water control and ventilation. In the field, ridge cultivation with plastic film is adopted, with ridges 30 cm high and covered with gray plastic film. Soil fertility is tested before transplanting: if the soil fertility is high, no fertilizer is applied; if the soil fertility is insufficient, 80 kg (approximately 160 catties) of well-rotted organic fertilizer is applied per acre. A wide-narrow row planting pattern is adopted, with the female parent QCBU-001 planted in 4 rows in the same bed, and the male parent 'Ningqin No. 1' planted in 1 row. The row spacing and plant spacing between the female and male parent rows are set to ensure that the male parent pollen can effectively cover the female parent population. Specifically: the plant spacing between both parents is set at 0.6 m; the row spacing between adjacent female parent rows within the same bed is 0.5 m, with 4 rows of female parents forming a 2 m wide female parent bed; the row spacing between the female parent bed and the adjacent male parent row is 0.5 m. A 0.25m edge distance is reserved on the outer side of the ridge strip. In the field, the ridge strips are arranged in a cyclical pattern of "mother plant ridge strip - 0.5m interval - father plant row - 0.5m interval - mother plant ridge strip". Figure 2 In this layout, the horizontal distance between the furthest row of female and male parents within the ridge is 1.5m. Within the effective diffusion range of celery pollen, this ensures that the male parent pollen fully covers the female parent population, meeting the requirements for hybridization pollination.

[0030] The following measures should be taken for the prevention and control of pests and diseases in the field: For blight of celery, use 45% chlorothalonil smoke agent for fumigation, at a rate of 100-150 g per acre, applied every 9 days; for rust of celery, use 50% carbendazim wettable powder for spraying, at a rate of 60-120 g per acre, diluted in 30 kg of water and sprayed evenly; for aphids, imidacloprid pesticides are prohibited, and 3% abamectin emulsifiable concentrate diluted 1000-2000 times should be sprayed by misting. Weeding in the field should be mainly done manually, regularly during the growing season, and weeding should be prohibited during the flowering period to avoid damaging the inflorescences and spreading mixed pollen; weed control fabric can be laid between furrows for physical weed control.

[0031] 4. Flowering period regulation and encounter adjustment After transplanting, the parent plants overwintered and completed vernalization under natural conditions. The following spring, as temperatures rose, they entered the bolting and flowering stage. The natural flowering period of the female parent, QCBU-001, was from mid-May to the end of June, while that of the male parent, 'Ningqin No. 1', was from early May to the end of May. To ensure that the flowering periods of the parents coincided, the following control measures were adopted: If the male parent flowered earlier than the female parent, the main flower stalk of the male parent was removed to promote lateral branching, thus delaying the flowering period of the lateral branches until after mid-May; if the male parent flowered later than the female parent, a 20–30 mg / L gibberellin solution was sprayed once at the early bolting stage of the male parent to promote earlier flowering. The female parent, QCBU-001, was not subjected to any flowering period control treatment and was allowed to flower naturally to avoid unpredictable impacts on the stability of its sterility trait. The control objective was to ensure that the peak flowering periods of the male and female parents coincided, with a continuous pollination window of no less than 15 days.

[0032] 5. Natural pollination in the field After the flowers of the celery sterile variety QCBU-001 unfold, the stigma secretes a viscous, liquid nectar that emits a faint fragrance. This nectar is highly attractive to pollinating insects such as bees and hoverflies. Simultaneously, the stickiness of the nectar helps to absorb pollen grains dispersed in the air. Therefore, no artificial pollination is used during the pollination period; pollen dispersal relies entirely on natural wind and insect activity. Figure 3 Maintain appropriate humidity in the field during the pollination period and avoid extreme weather such as strong winds and heavy rains that could significantly affect pollination.

[0033] When most plants in the female parent QCBU-001 population have completed pollination of their fifth-order inflorescences (i.e., the fifth branching inflorescence of the compound umbel), their petals have fallen, and their seeds have begun to swell, this is the appropriate time to remove the male parent. At this time, use a sickle to cut all male parent plants at the base in the field. The removed male parent plants should be immediately cleared from the field and must not be left in the seed production field to prevent male parent seeds from mixing with the hybrid seeds during harvest. After the male parent is removed, the female parent plants enter the seed development stage. During this period, continue to manage pests and diseases, using the same pesticide regimen as during the transplanting stage, focusing on controlling aphids and rust.

[0034] 6. Seed harvesting and post-harvest treatment The seed development of the parent plant QCBU-001 exhibits the following characteristics: the seeds are capable of falling off before they are fully mature, even as they transition from green to yellow; therefore, precise timing of harvesting is crucial. When the seeds of the fifth-order inflorescence on the parent plant begin to turn from green to yellow, it indicates that the seeds of the earlier-developing first to fourth-order inflorescences on the parent plant have all matured. Harvesting must begin immediately to prevent the premature detachment of mature seeds and subsequent yield loss. Harvesting is done by cutting the parent plant at ground level with a sickle and spreading the harvested plants out on non-woven fabric or a cement drying area to dry.

[0035] After drying for 3-5 days, the seeds are threshed. The threshed seeds contain a large amount of impurities such as flower stalks, glumes, and debris. These are separated using an agricultural grain winnowing machine, with the airflow adjusted to ensure thorough separation of the clean seeds from the impurities, resulting in pure hybrid seeds. The pure seeds are then further dried until the moisture content drops below 8%, and then stored in airtight, waterproof, and moisture-proof bags. The sealed bags are then stored at room temperature (15-25℃) for approximately 2 months to allow the hybrid seeds to complete ripening and break dormancy.

[0036] Germination tests showed a germination rate of over 85%, meeting the standards for use and allowing for packaging and commercial production. Each acre can yield over 300 jin of hybrid seeds (100-200 jin for self-pollination or conventional seed production), with high seed uniformity and quality (0.8-1.0 g per thousand seeds, 0.5-0.8 g for commercial seeds), reducing hybrid seed production costs.

[0037] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for seed production using celery male-sterile strain QCBU-001 hybridization, characterized in that, Includes the following steps: Sowing and seedling raising: At the end of October, the female seeds of male sterile celery QCBU-001 and the male seeds of fertile celery were sown in seedling trays respectively. After sowing, no soil was covered. Water was supplied by bottom watering. When the seedlings grew to the 3-leaf stage, they were transplanted into 72-cell seedling trays and continued to be cultivated until the 5-leaf stage. Field transplanting: After hardening off the seedlings at the 5-leaf stage, transplant them into the field with mulched ridges. Plant the female parent in 4 rows in the same ridge, and plant the male parent in 1 row. The spacing between female parent plants is 0.6m and the row spacing is 0.5m. The spacing between male parent plants is 0.6m. The distance between the male parent row and the adjacent female parent ridge is 0.5m. The arrangement is in a unit cycle of "female parent ridge - male parent row - female parent ridge". Flowering period control: The female parent flowers naturally. When the male parent flowers earlier than the female parent, remove the main stem of the male parent. When the male parent flowers later than the female parent, spray the male parent with gibberellin solution. Field pollination: Pollination is completed by natural wind and pollinating insects. When the fifth inflorescence of the female plant has finished pollination and the seeds begin to swell, all male plants in the field are cut off. Seed harvesting: When the seeds of the fifth inflorescence of the mother plant turn from green to yellow, the mother plant is cut off, dried, threshed, and the seeds are winnowed to obtain pure seeds. After drying until the moisture content is below 8%, the seeds are sealed and stored.

2. The method according to claim 1, characterized in that, The fertile male parent is selected from any one of 'Ningqin No. 1', 'Ningqin No. 2', 'Ventura', 'Huai'an Medicinal Celery', 'Guiyang Small Celery', 'Nanxuan Liuhe Purple Celery', or 'Chengdu White Celery'.

3. The method according to claim 1, characterized in that, In the sowing and seedling raising process, the seedling tray is 60cm long, 30cm wide, and 3.3cm high, and the bottom of the tray has drainage holes.

4. The method according to claim 1, characterized in that, In the sowing and seedling raising process, 300 seeds are sown in each tray, and the moisture content of the nutrient soil is 70% to 80% of the field water holding capacity. After germination, the substrate moisture content is maintained at 60% to 80%.

5. The method according to claim 1, characterized in that, In the field transplanting process, the ridge height is 30 cm, and the ridge surface is covered with gray mulch. Before transplanting, the field fertility is tested. If the fertility is high, no fertilizer is applied. If the fertility is insufficient, 80 kg of well-rotted organic fertilizer is applied per mu.

6. The method according to claim 1, characterized in that, In the field transplanting process, the seedling hardening time is 7 days, which is carried out by controlling water and ventilation.

7. The method according to claim 1, characterized in that, During the field planting process, pest and disease control measures are as follows: for celery blight, use 45% chlorothalonil fumigant at a rate of 100-150 g per acre, applied every 9 days; for celery rust, use 50% carbendazim wettable powder at a rate of 60-120 g per acre; and for aphids, use 3% abamectin emulsifiable concentrate diluted 1000-2000 times and sprayed.

8. The method according to claim 1, characterized in that, In the flowering period control steps, when the male parent flowers later than the female parent, the concentration of gibberellin solution sprayed should be 20-30 mg / L, and sprayed once at the early stage of bolting of the male parent.

9. The method according to claim 1, characterized in that, During the seed harvesting process, the seed is dried for 3 to 5 days, then sealed and stored at room temperature (15 to 25°C) for 2 months.

10. The application of the method according to any one of claims 1-9 in improving the yield, uniformity, and quality of celery hybrid seed production.

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