A method for identifying and selecting celery plants with tolerance to bolting

Abstract

The application discloses a celery bolting resistance identification and seedling selection method, which can simultaneously accurately investigate and identify important agronomic characters and bolting resistance of celery, and breed bolting resistance celery variety materials in time by combining seedling selection, is reasonable and efficient in time arrangement. Under the cultivation condition of a winter-spring sunlight greenhouse, different celery varieties have obvious differences in bolting performance, and field investigation is convenient, fast and accurate. A bolting index is used as a bolting resistance grading evaluation standard of celery, which is consistent with the variety characteristics of poor bolting consistency in the same celery variety population. The application adopts a hard engraver, vertically inserts the engraver into a center part of a seedling from a side, cuts off the center leaf, and pulls out the cut leaf upwards, so that celery seedling leaf stalk damage can be reduced as much as possible, and the bolting resistance celery material can be ensured to survive quickly after planting.

Description

Technical Field

[0001] This invention belongs to the field of vegetable breeding technology, specifically relating to a method for identifying bolting resistance in celery and selecting seed plants. Background Technology

[0002] Celery (Apium graveolens L. var. dulce) is a biennial vegetable belonging to the genus Apium of the family Apiaceae. Rich in nutrients and possessing various pharmacological functions, it is renowned as a valuable vegetable and medicine, and is cultivated throughout my country. In northern regions, utilizing greenhouses or plastic tunnels for spring celery production is a crucial cropping arrangement. However, the prolonged low temperatures and gradual temperature changes in spring, along with the increasing daylight hours, perfectly meet the vernalization, bolting, and flowering requirements of celery (Pressman, 1997), easily leading to premature bolting. This not only reduces celery quality but also limits yield (Jenni et al., 2005). Breeding bolting-resistant celery varieties for spring production can effectively address this problem (Wolf et al., 1993).

[0003] Celery is a typical vernalization plant. To fully experience the low-temperature vernalization stimulus, celery generally needs to have at least four true leaves and be kept at a low temperature of 5-8℃ for more than six weeks before bolting and flowering under long-day conditions (Quiros, 1993). In celery breeding, vernalization is generally completed in a greenhouse. Flower stalks begin to elongate in mid-February, with different varieties exhibiting varying rates of elongation. By late March, flower stalks of easily bolting varieties can reach over 10 cm in length, while those of bolting-resistant varieties remain quite short. During this period, the basic agronomic traits of celery are fully expressed, making it ideal for observing the agronomic traits of breeding materials, identifying bolting characteristics, and selecting superior seed plants. By late March or early April, the selected celery seed plants are transplanted into the field for propagation. After this period, as the outside temperature rises, celery will show signs of aging such as pithiness and water stains, and the flower stalks of easily bolting varieties will also elongate rapidly. All of these factors directly affect the survival rate of the seedlings after transplanting. Therefore, the identification of bolting tendency and the selection of bolting-resistant materials should not be done too early or too late.

[0004] It is important to note that when bolting is assessed in late March, the celery flower stalk is tightly wrapped inside the plant by multiple layers of fleshy petioles. In the past, to measure the length of the flower stalk of a celery variety and determine the timing of bolting, the plant was longitudinally split in the middle to expose the flower stalk for measurement. Figure 1The fatal flaw of this method is that the plants cannot survive after being longitudinally cut and cannot be used as seed plants. In celery breeding, the conventional method for selecting seed plants is to first dig up celery plants with good overall performance, then make a horizontal cut at a height of 15-20cm, removing the upper petioles, leaves, and outer old leaves; these are then ready for transplanting and propagation. To select plants with short flower stalks, the horizontal cut was previously made gradually downwards until it reached the top of the flower stalk. All plants were then cut at this slightly higher point, and any plants clearly cut to the flower stalk were discarded; those not cut to the flower stalk were retained for propagation. The disadvantage of this method is that the horizontal cut height cannot be too low, meaning the selection pressure for bolting resistance cannot be too great. A cut point that is too low will cause excessive damage to the plant, leaving too small a vegetative body, making it difficult to ensure survival after transplanting, thus resulting in the loss of selected bolting-resistant breeding material. Summary of the Invention

[0005] The purpose of this invention is to provide a method for identifying and selecting bolting-resistant celery plants, which provides a simple, selective, and high-survival-rate method for bolting-resistant celery breeding, and can greatly improve the efficiency of bolting-resistant celery breeding.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for identifying bolting resistance in celery and selecting seed plants includes the following steps:

[0008] (1) Sowing and seedling raising: Green Giant, a celery variety prone to bolting, was used as a control variety. The new seeds of all celery varieties that participated in the bolting resistance assessment were sown in seedling trays filled with sterilized nutrient soil in late August and managed during the seedling stage according to conventional seedling raising methods.

[0009] (2) Transplanting and planting: In late October, 60-day-old celery seedlings with 4 healthy true leaves and well-developed root systems were transplanted to the cultivation beds in the greenhouse. The planting rows were oriented north-south, with a plant spacing of 15cm × 20cm. Two rows were planted for each tested variety, with 40 seedlings in each row.

[0010] (3) Post-transplanting management: After transplanting, keep the soil moist to facilitate seedling establishment and root development. After a short period of hardening off, increase the supply of fertilizer and water, and maintain a relatively high temperature in the greenhouse to promote celery growth. As the soil temperature in the greenhouse drops significantly, reduce the supply of fertilizer and water and increase ventilation during high-temperature periods. When the soil temperature in the greenhouse begins to rise steadily, gradually increase the supply of fertilizer and water to meet the needs of rapid celery growth and promote the early expression of basic celery varietal traits. When the outside temperature begins to rise, pay attention to extending the ventilation time and increasing the ventilation volume to enhance the adaptability of celery and prepare for transplanting seedlings. Implement pest and disease control measures throughout the entire process.

[0011] (4) Agronomic trait survey: By mid-to-late March, after the celery has fully grown and developed in the greenhouse, all the characteristics of the varieties have been expressed. The agronomic traits of each celery variety are investigated. Based on the overall performance of each variety in the field, seed selection is carried out, and inferior plants are eliminated.

[0012] (5) Bolting tolerance survey: By mid-to-late March, the flower stalks of the control variety Green Giant had grown to over 10 cm. Ten plants were randomly selected from each variety as samples for the bolting tolerance survey. Each plant was longitudinally sectioned, and the length of the flower stalk was measured. Bolting was graded according to the following criteria:

[0013] Grade 0: Flower stalk length is 0cm;

[0014] Grade 1: Flower stalk length is 0-1.5cm;

[0015] Grade 3: Flower stalk length is 1.5-3cm;

[0016] Grade 5: Flower stalk length is 3-6cm;

[0017] Level 7: Flower stalks are 6-10cm long;

[0018] Level 9: Flower stalks are longer than 10cm.

[0019] (6) Evaluation criteria for bolting resistance: Based on the results of the bolting grading survey, the bolting index of each variety of material is calculated using the following formula.

[0020] Bolting Index BI = [∑(bolting level × number of plants surveyed at each level) / (highest level × total number of plants surveyed)] × 100

[0021] The bolting resistance of the tested celery varieties was graded and evaluated according to the bolting index:

[0022] Extremely resistant to bolting (HT): 0 ≤ BI < 15;

[0023] Bolting resistance (T): 15 ≤ BI < 35;

[0024] Medium bolting resistance (MT): 35 ≤ BI < 55;

[0025] Bolting tendency (S): 55 ≤ BI < 85;

[0026] Extremely prone to bolting (HS): BI≥85.

[0027] (7) Selection of bolting-resistant seedlings: First, based on the agronomical characteristics, select seedlings from all celery varieties and make horizontal cuts at a height of 15-20cm, removing the upper petioles, leaves, and outer old leaves. Then, based on the bolting resistance assessment results from the previous step, use a hard-edged knife with a 1.5cm blade to vertically insert into the center of the seedling at heights of 1-1.5cm, 1.5-3cm, and 3-6cm for extremely bolting-resistant, bolting-resistant, and moderately bolting-resistant varieties, respectively. While minimizing damage to the surrounding petioles, cut off the central leaves and lift the cut leaves upwards to pull them out. Carefully examine the cut surfaces of the protruding leaves; any seedlings found to have reached the flower stalk are discarded, while all seedlings not cut to the flower stalk are retained for planting and propagation.

[0028] Advantages of this invention:

[0029] 1. It can simultaneously conduct accurate investigations and identifications of important agronomic traits and bolting resistance of celery, and combine seed selection and retention to promptly propagate bolting-resistant celery varieties with reasonable and efficient time arrangements.

[0030] 2. Using Green Giant, a celery variety prone to bolting, as a control variety, the bolting performance of different celery varieties showed significant differences under winter and spring greenhouse cultivation conditions, making field surveys convenient, quick, and accurate.

[0031] 3. The bolting index is used as the evaluation standard for the bolting resistance of celery, which is consistent with the seed characteristics of poor bolting uniformity within the same celery variety population.

[0032] 4. To assess and select for different varieties with varying degrees of bolting resistance, a hard carving knife is inserted into the plant at the corresponding height for each variety to cut off the central leaves. This process ensures optimal selection pressure.

[0033] 5. Use a hard carving knife to vertically insert it from the side of the celery plant to cut off the central leaf. Then, lift the cut leaf upwards and pull it out. This will preserve as many of the outer petioles of the celery plant as possible, greatly reducing the degree of damage. This is a key measure to ensure that bolting-resistant celery materials can survive quickly after transplanting. Attached Figure Description

[0034] Figure 1 This is a longitudinal section used in conventional methods to investigate bolting in celery plants.

[0035] Figure 2 It involves inserting a hard carving knife into the side of the celery plant and lifting the central leaf upwards.

[0036] Figure 3 It is a celery stalk after the central leaf has emerged.

[0037] Figure 4This is a celery seed production field after the seed plants have been planted. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, unless otherwise specified, the specific experimental methods involved in the following embodiments are conventional methods or implemented according to the conditions recommended in the manufacturer's instructions.

[0039] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the experimental methods in the following embodiments are all conventional methods. Unless otherwise specified, the reagents and materials used can be purchased commercially.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be used in this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0041] Example

[0042] (1) Celery varieties used in the test

[0043] Twelve celery self-pollination materials, including Ventura, Green Giant, K01-6, D03-5, R05-20, T06-15, B20-183, R21-3, S54, S80, S236, and S430, were selected as experimental materials for identifying celery bolting resistance and selecting seed plants. Ventura and Green Giant are commercially available celery varieties, while K01-6, D03-5, R05-20, T06-15, B20-183, R21-3, S54, S80, S236, and S430 are selected self-pollination materials from the preferred offspring of commercially available varieties. These materials can be obtained from the Celery Research Group of the Vegetable Research Institute of Tianjin Academy of Agricultural Sciences for the purpose of replicating the relevant experiments of this invention. Preliminary experiments have shown that Green Giant is a celery variety prone to bolting.

[0044] (2) Sowing and seedling raising: In late August, all the new seeds of the year from the celery varieties that participated in the bolting resistance evaluation were sown in seedling trays filled with sterilized nutrient soil and managed in accordance with conventional seedling raising methods.

[0045] (3) Transplanting and planting: In late October, 60-day-old celery seedlings with 4 healthy true leaves and well-developed root systems were transplanted into the cultivation beds of the greenhouse. The planting rows were oriented north-south, with a plant spacing of 15cm × 20cm. Each tested variety was planted in 2 rows, with 40 plants in each row.

[0046] (4) Post-transplanting management: After transplanting, keep the soil moist to facilitate seedling establishment and root development. After a short period of hardening off, increase the supply of fertilizer and water, and maintain a relatively high temperature in the greenhouse to promote celery growth. As the soil temperature in the greenhouse drops significantly, reduce the supply of fertilizer and water and increase ventilation during high-temperature periods. When the soil temperature in the greenhouse begins to rise steadily, gradually increase the supply of fertilizer and water to meet the needs of rapid celery growth and promote the early expression of basic celery varietal traits. When the outside temperature begins to rise, pay attention to extending the ventilation time and increasing the ventilation volume to enhance the adaptability of celery and prepare for transplanting seedlings. Implement pest and disease control measures throughout the entire process.

[0047] (5) Agronomic trait survey: By mid-to-late March, after the celery has fully grown and developed in the greenhouse, all the characteristics of the varieties have been expressed. The agronomic traits of each celery variety are investigated. Based on the overall performance of each variety in the field, seed selection is carried out, and inferior plants are eliminated.

[0048] (6) Bolting tolerance survey: By mid-to-late March, the flower stalks of the control variety Green Giant had grown to over 10 cm. Ten plants were randomly selected from each variety as samples for the bolting tolerance survey. Each plant was longitudinally sectioned, and the length of the flower stalk was measured. Bolting was graded according to the following criteria:

[0049] Grade 0: Flower stalk length is 0cm;

[0050] Grade 1: Flower stalk length is 0-1.5cm;

[0051] Grade 3: Flower stalk length is 1.5-3cm;

[0052] Grade 5: Flower stalk length is 3-6cm;

[0053] Level 7: Flower stalks are 6-10cm long;

[0054] Level 9: Flower stalks are longer than 10cm.

[0055] (7) Evaluation criteria for bolting resistance: Based on the results of the bolting grading survey, the bolting index of each variety of material is calculated using the following formula.

[0056] Bolting Index (BI) = [∑(bolting grade × number of plants surveyed at each grade) / (highest grade × total number of plants surveyed)] × 100

[0057] The bolting resistance of the tested celery varieties was classified and evaluated according to the bolting index:

[0058] Extremely resistant to bolting (HT): O≤BI<15;

[0059] Bolting resistance (T): 15 ≤ BI < 35;

[0060] Medium bolting resistance (MT): 35 ≤ BI < 55;

[0061] Bolting tendency (S): 55 ≤ BI < 85;

[0062] Extremely prone to bolting (HS): BI≥85.

[0063] (8) Results of bolting resistance assessment

[0064] The bolting resistance assessment results for this example are shown in Table 1. When the bolting degree of the comparative variety Green Giant reached level 9, no variety among the 12 celery varieties tested was found to be completely non-bolting. The bolting index of "R21-3" was 11.11, less than 15, classifying it as an extremely bolting-resistant variety. The bolting indices of three varieties, "K01-6," "R05-20," and "S80," were between 15 and 35, classifying them as bolting-resistant varieties. The bolting indices of three varieties, "D03-5," "S236," and "Ventura," were between 35 and 55, classifying them as moderately bolting-resistant varieties. The bolting indices of four varieties, "T06-15," "B20-183," "S54," and "S430," were between 55 and 85, classifying them as easily bolting varieties. Green Giant... The bolting index of "Giant" was 95.56, far greater than 85, indicating that it is an extremely bolting-prone variety. The identification results of this example are consistent with the bolting performance of these varieties in actual production, demonstrating that this method for identifying celery bolting resistance is accurate, highly comparable, easy to operate, and highly efficient.

[0065] Table 1. Results of bolting resistance assessment of 12 celery breeding materials

[0066] Serial Number Celery ingredients Bolting index Bolting resistance level 1 K01-6 33.33 T 2 D03-5 46.67 MT 3 R05-20 31.11 T 4 T06-15 64.44 S 5 B20-183 82.22 S 6 R21-3 11.11 HT 7 S54 75.56 S 8 S80 33.33 T 9 S236 40.00 MT 10 S430 77.78 S 11 Ventura 40.00 MT 12 Green Giant (Comparison Variety) 95.56 HS

[0067] (8) Selection of bolting-resistant seedlings: First, based on the agronomical characteristics, select seedlings from all celery varieties and make horizontal cuts at a height of 15cm, removing the upper petioles, leaves, and outer old leaves. Then, based on the results of the bolting resistance survey in the previous step, use a hard carving knife with a blade width of 1.5cm to vertically insert into the center of the seedling from the side at heights of 1.5cm, 3cm, and 4cm for extremely bolting-resistant, bolting-resistant, and moderately bolting-resistant varieties, respectively, to cut off the central leaves, taking care to preserve the surrounding petioles. Then, lift the cut leaves upwards and pull them out. Figure 2 and Figure 3 Carefully examine the cut ends of the protruding leaves. Discard any plants that have been cut to the flower stalk, and retain all plants that have not been cut to the flower stalk for propagation. Figure 4 The exhibition showcases celery seed production fields after selecting and planting superior seed plants.

[0068] The inventors also compared different seed-saving methods: (1) Conventional transverse cutting method: petiole is cut 15cm; (2) Short transverse cutting method: petiole is cut down to the upper part of the celery flower stalk; (3) Insertion cutting method (method of this invention): after the petiole is cut 15cm, the knife is vertically inserted into the seed plant on the side of the upper part of the celery flower stalk, the central leaf is cut off and the central leaf is pried out, and the surrounding petioles are preserved.

[0069] Table 2 lists the elimination rate and transplant survival rate of bolt-resistant celery seedlings selected using different leaf-cutting methods for five celery varieties. The results show that the conventional method of cutting celery seedlings at a height of 15cm in late March definitely fails to cut the flower stalks, thus having no selection effect; the elimination rate is 0 in all cases. Seedlings cut at a height of 15cm leave a sufficiently large vegetative body to meet their own nutritional needs during the transplanting and seedling establishment process, resulting in a 100% survival rate. When the cutting height is significantly lowered, seedlings that reach the flower stalks are eliminated, while those that do not reach the flower stalks have significantly smaller vegetative bodies. During the transplanting and seedling establishment process, their nutritional needs cannot be met in time, leading to a large number of seedling deaths and a generally low survival rate. The extremely bolting-resistant R21-3, when cut transversely at 1.5cm, had a transplant survival rate of only 10%. The bolting-resistant K01-6, R05-20, and S80, when cut transversely at 3.0cm, had survival rates of 31.2%, 23.7%, and 23.5%, respectively. The moderately bolting-resistant S236, when cut transversely at 4.0cm, had a survival rate of 25%. This invention, using an insertion cutting method, only cuts and pulls out the central leaf of the plant at a lower position, while retaining the surrounding 15cm thick petioles. This treatment of various celery materials resulted in a rejection rate very close to that of the short transverse cutting method, indicating that it maintained a good bolting-resistant selection effect. All plants survived after transplanting and could successfully bolt, flower, and be used for seed production, thus greatly improving the efficiency of bolting-resistant breeding.

[0070] Table 2. Comparison of the effects of different treatments on seed plants of five bolting-resistant celery varieties.

[0071]

[0072]

[0073] Note 1: The leaf cutting treatment was performed in late March. The average length of the flower stalks of the comparison variety Green Giant was 11.3 cm.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A method for identifying bolting resistance in celery and selecting seed plants, characterized in that, The method includes the following steps: (1) Sowing and seedling raising; (2) Transplanting and planting; (3) Post-planting management; (4) Agronomic traits survey: By mid-to-late March, the agronomic traits of each celery variety were surveyed; based on the overall field performance of each variety, seed selection was carried out and inferior plants were eliminated. (5) Bolting resistance survey: By mid-to-late March, the flower stalks of the comparison variety Green Giant had grown to more than 10cm; 10 plants were randomly selected from each variety as bolting resistance survey samples, and each plant was longitudinally cut to measure the length of the flower stalk. Based on the length of the flower stalk, the bolting grade survey results of celery were divided into grades 0, 1, 3, 5, 7 and 9. (6) Evaluation criteria for bolting resistance: Based on the results of the bolting grading survey, the bolting index of each variety of material is calculated using the following formula; Bolting index BI = [∑(bolting level × number of plants investigated at each level) / (highest level × total number of plants investigated)] × 100. The bolting resistance of the tested celery varieties is graded and evaluated according to the bolting index. (7) Selection of bolting resistant seed plants: First, based on the agronomic characteristics of all celery varieties, the seed plants initially selected are cut horizontally at a height of 15-20cm, and the upper petioles, leaves and outer old leaves are removed. Based on the results of the previous bolting tolerance grading survey, at heights of 1-1.5cm, 1.5-3cm, and 3-6cm for extremely bolting tolerant, bolting tolerant, and moderately bolting tolerant varieties, a hard carving knife with a blade width of 1.5cm was used to vertically insert into the center of the plant from the side, cutting off the central leaf. The cut leaf was then lifted upwards and pulled out. The cut of the leaf was carefully examined. Any plant that had been cut to the flower stalk was discarded, while all plant that had not been cut to the flower stalk were retained for planting and propagation.

2. The method according to claim 1, characterized in that, The specific steps of sowing and seedling raising in step (1) are as follows: using Green Giant, a celery variety that is prone to bolting, as a control variety, the new seeds of all celery varieties that participated in the bolting resistance assessment were sown in seedling trays containing sterilized nutrient soil in late August, and seedling management was carried out in accordance with conventional seedling raising methods.

3. The method according to claim 1, characterized in that, The specific steps for transplanting and planting in step (2) are as follows: In late October, 60-day-old celery seedlings with 4 healthy true leaves and well-developed root systems are transplanted to the cultivation beds in the solar greenhouse. The planting rows are oriented north-south, and the plant spacing is 15cm×20cm. Each tested variety is planted in 2 rows, with 40 plants in each row.

4. The method according to claim 1, characterized in that, The specific management methods described in step (2) after transplanting are as follows: After transplanting, keep the soil moist to facilitate seedling establishment and rooting. After a short period of hardening off, increase the supply of fertilizer and water, maintain a high temperature in the greenhouse, and promote the growth of celery. As the soil temperature in the greenhouse drops significantly, reduce the supply of fertilizer and water and increase ventilation during high-temperature periods. When the soil temperature in the greenhouse begins to rise continuously, gradually increase the supply of fertilizer and water to meet the needs of rapid growth of celery and promote the early expression of the basic varietal traits of celery. When the outside temperature begins to rise, pay attention to extending the ventilation time and increasing the ventilation volume to enhance the adaptability of celery and prepare for the transplanting of seedlings. Do a good job in the prevention and control of diseases and pests throughout the process.

5. The method according to claim 1, characterized in that, The criteria for evaluating bolting resistance in step (6) are as follows: Extremely resistant to bolting: 0 ≤ BI < 15; Bolting tolerance: 15 ≤ BI < 35; Moderate bolting resistance: 35 ≤ BI < 55; Bolting tendency: 55 ≤ BI < 85; Extremely prone to bolting: BI≥85.

6. The method according to claim 1, characterized in that, When inserting the plant vertically from the side to the center in step (7), try to minimize damage to the surrounding petioles.

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