Method for improving seedling survival rate of poplar hybrid seeds

Abstract

The invention provides a method for improving the seedling survival rate of poplar hybrid seeds, and belongs to the technical field of forest clone breeding. According to the method, seed vigor grading, compound matrix proportioning, precise temperature and humidity regulation and control and progressive stress seedling hardening technologies are integrated, and a poplar hybrid seed seedling raising system integrating seed vigor keeping, precise environment regulation and control and comprehensive pest and disease damage prevention and control is adopted, so that the survival rate and quality of hybrid seed seedling raising are remarkably improved; the germination rate of the obtained hybrid seeds is 92% or above, seedlings are robust and grow vigorously, the proportion of robust seedlings with the height larger than or equal to 15 cm is 90%, the field transplanting survival rate is larger than or equal to 95%, the cross breeding achievement is effectively guaranteed, and the method is particularly suitable for treating hybrid seed populations uneven in maturity.

Description

Technical Field

[0001] The invention relates to the technical field of forest tree clone breeding, and in particular to a method for improving the survival rate of poplar hybrid seed seedlings. Background Art

[0002] Poplar is a general term for deciduous trees of the genus Populus in the family Salicaceae. There are many species of poplars with remarkable characteristics such as rapid growth, strong adaptability, and excellent material quality. They occupy a pivotal position in forestry production and ecological construction. At present, the European and American poplar and American black poplar varieties promoted and applied in production are mainly bred through hybrid breeding. Hybrid breeding is an important method for breeding new poplar varieties. The main methods of poplar hybrid breeding are wild large tree hybridization and indoor cutting hydroponic hybridization. Although wild large tree hybridization can obtain a large number of full seeds, it has disadvantages such as high cost and high risk of high-altitude operations. Indoor cutting hydroponics can concentrate the scattered mother plants for hybridization, provide a variety of hybrid combinations, quickly achieve breeding goals, and have the advantages of convenient management and low cost. It has become a commonly used method for poplar hybrid breeding at home and abroad.

[0003] However, during the hybrid breeding process of poplar cuttings and hydroponics, the number of seeds obtained is limited, and each hybrid seed is extremely precious. How to improve the germination rate of these hybrid seeds and then cultivate strong seedlings has become a key link in the success of hybrid breeding. Given that poplar seeds are short-lived and the vitality of hybrid seeds is lower than that of naturally strong seeds, this undoubtedly increases the difficulty of breeding. The current hybrid seed breeding process faces the following technical bottlenecks: (1) Uneven seed maturity: In indoor hydroponic hybridization of cuttings, the maturity period of capsules on different branches and even capsules in different parts of the same branch are significantly different. This inconsistency in maturity directly causes uneven seed vitality, which seriously affects the uniformity and stability of seedling cultivation. (2) Low germination rate: Hybrid seeds are less vigorous than naturally hardened seeds. Using conventional seedling cultivation methods, their germination rate is often not high. In addition, the seedlings have poor adaptability to the environment and are easily affected by fluctuations in environmental factors such as temperature and humidity, which in turn affects the normal growth of the seedlings. (3) Low survival rate of seedling hardening: Traditional seedling hardening methods lack sufficient consideration of the growth characteristics of seedlings and do not design a gradual environmental adaptation process. As a result, it is difficult for seedlings to quickly adapt to the field environment after transplanting, and their stress resistance is poor, which ultimately leads to a low survival rate in the field.

[0004] For a long time, existing technologies have lacked comprehensive and systematic solutions to these problems, which has, to a certain extent, restricted the in-depth development of poplar hybrid breeding and affected the efficiency of selecting high-quality hybrid varieties. Therefore, in order to overcome these technical bottlenecks and improve the survival rate and quality of poplar hybrid seed seedlings, a new seedling cultivation method specifically for poplar hybrid seeds is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the survival rate of poplar hybrid seed seedlings, which significantly improves the survival rate and quality of hybrid seed seedlings. The germination rate of the obtained hybrid seeds is above 92%, and the seedlings are strong and grow vigorously.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for improving the survival rate of poplar hybrid seed seedlings, comprising the following steps: (1) Seed grading: The seeds were grouped and cultured, and the germination rate of each seed group was counted. The seeds were then divided into high-vigor seeds, medium-vigor seeds, and low-vigor seeds based on the germination rate. The high-vigor seeds were sown directly, the medium-vigor seeds were soaked and then sown, and the low-vigor seeds were treated with tissue culture technology. (2) Sowing and raising seedlings: The seeds treated in step (1) were planted in seedling trays and cultured until the seedlings had 4 true leaves; (3) Gradual stress hardening Ridge the seedbed, and then plant the seedlings grown to 4 true leaves in step (2) in the seedbed for hardening; (4) When the seedlings in step (3) grow to a height of ≥15 cm, transplanting and planting begins.

[0007] Preferably, in step (1), the high-vigor seeds are seeds with a germination rate greater than 85%, the medium-vigor seeds are seeds with a germination rate of 60%-85%, and the low-vigor seeds are seeds with a germination rate less than 60%.

[0008] Preferably, in step (1), the tissue culture comprises the following steps: Soak the seeds in 75% alcohol for 1 minute, rinse with sterile water, take out the seeds, and inoculate them into MS culture medium until seedlings emerge.

[0009] Preferably, in step (2), the structure of the seedling tray is: Bottom layer: peat soil: perlite volume ratio = 2-4:1-2, thickness 2-4cm; Middle layer: 0.5-1mm vermiculite, thickness 1-2cm; Surface layer: slow-release fertilizer.

[0010] Preferably, in step (2), the conditions for culturing the seedlings to 4 true leaves are: During the germination period 1-2 days after sowing, control the temperature at 19-23°C, humidity at 70%-80%, and shading rate at 40-60%.

[0011] Seedling stage from emergence to 4 true leaves: temperature 24-28℃, humidity 50-60%, daily light 10-14 hours, intensity 8000-10000 lux.

[0012] Preferably, in step (3), the parameters of the ridge formation are: ridge height 20-30 cm, ridge width 45-55 cm, and ridge spacing 0.5 m.

[0013] Preferably, in step (3), the step of hardening the seedlings includes: Day 1-3: Light intensity 6000±500 lux, watering 1-2 times a day, substrate humidity ≥70%; Day 4-7: Light intensity 8000±500 lux, humidity reduced to 40-50%; Day 8-14: Natural light, intermittent watering, and water replenishment when humidity is ≤30%.

[0014] Preferably, in step (4), the planting row spacing is: plant spacing 25-30 cm, and row spacing 80-100 cm.

[0015] The beneficial effects of the present invention compared with the prior art are: (1) The present invention integrates seed vigor grading, composite matrix ratio, precise control of temperature and humidity, and progressive stress hardening technology to form a poplar hybrid seed seedling system that combines seed vigor maintenance, precise environmental control, and integrated pest and disease control. This significantly improves the survival rate and quality of hybrid seed seedlings. The resulting hybrid seeds have a germination rate of over 92%, and the seedlings are robust and grow vigorously, effectively ensuring the results of hybrid breeding. The system is particularly suitable for treating hybrid seed populations with uneven maturity.

[0016] (2) The seed grading process of the present invention can screen out low-vitality seeds by measuring germination rates, and adopt embryo rescue technology to ensure that all seeds can be effectively utilized, so that the germination rate of hybrid seeds in the seedling stage is ≥92%, which is 25%-30% higher than the original traditional method. During the seedling raising process, the bottom layer of the seedling tray (peat soil: perlite = 2-4:1-2) retains water and is breathable, the middle layer (vermiculite) promotes root development, and the surface layer (slow-release fertilizer) provides continuous nutrition.

[0017] (3) The progressive stress hardening of the present invention enhances the stress resistance of seedlings by regulating light, humidity and water deprivation in stages. The survival rate of seedlings is ≥95%, which is 15% higher than that of the original traditional method. In addition, the proportion of strong seedlings with a height of ≥15 cm is 90%, which is 20% higher than that of the original traditional method. The survival rate of transplanting in the field after transplanting is ≥95%, which is 20% higher than that of the original traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The high-vigor seeds in Example 1 of the present invention; Figure 2 The low-vigor seeds in Example 1 of the present invention; Figure 3 The tissue culture seedlings are the low-vigor seeds in Example 1 of the present invention; Figure 4 The poplar seedlings in the germination stage in Example 1 of the present invention; Figure 5 The poplar seedlings with 4 true leaves in Example 1 of the present invention; Figure 6 The poplar seedlings during outdoor hardening in Example 1 of the present invention; Figure 7 These are the poplar seedlings planted in the field in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting 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 terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0022] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0023] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

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

[0025] Hardware measures of embodiment 1 of the present invention: (1) Use solar greenhouses or plastic greenhouses. The greenhouses provide sufficient light, which helps to ensure that the seedbeds are exposed to sunlight for a longer period of time and to increase the temperature of the seedbeds, thus promoting seed germination. At the same time, the greenhouses are equipped with corresponding temperature control equipment and sunshade equipment to keep the temperature at 25°C-32°C, which is conducive to the germination of hybrid seeds and the healthy growth of hybrid seedlings.

[0026] (2) Seedbed rack: The width of the seedbed rack can be 1.5m-1.8m, and the height should be 0.5m-0.7m from the ground. A space of 0.5m should be reserved between every two groups of seedbed racks as an operating channel.

[0027] (3) Sprinkler irrigation facilities: equipped with automatic or human-powered mobile sprinkler vehicles. The hoisting position should be 0.5m-0.7m away from the seedbed. The number of sprinkler heads should be increased at both ends of the sprinkler vehicle. The water fineness of the sprinkler heads should be above 1000 mesh. A handheld water spray gun with a fineness higher than 1000 mesh should also be equipped for local water replenishment.

[0028] Example 1

[0029] Example 1 of the present invention provides a method for improving the survival rate of poplar hybrid seed seedlings, the specific steps of which are as follows: (1) Harvesting poplar hybrid seeds When the capsule skin turns yellow, cover it with a high-density nylon mesh bag to prevent the seeds from flying. Harvest after 1 / 2 of the capsules have cracked, separate the seed fluff, and place it in a ziplock bag. Store in a cool environment at 4°C and sow within 5 days.

[0030] (2) Seed viability determination and embryo rescue 100 poplar hybrid seeds were randomly selected as a group and placed in a culture dish (humidity 70%) with sterile filter paper. They were cultured at 25°C for 3 days, and the germination rate of each group of seeds was calculated.

[0031] Grading of seeds by germination rate test: Seeds with high vigor (>85%) can be sown directly, e.g. Figure 1 shown.

[0032] Medium-vigor seeds (60%-85%) should be soaked in 0.1% gibberellin solution for 2 hours before sowing.

[0033] Low vigor seeds (<60%, e.g. Figure 2 As shown): Using tissue culture technology, soak the seeds in 75% alcohol for 1 minute, rinse with sterile water 3 times, take out the seeds, inoculate them into MS culture medium, culture at 25±2℃ light (12h / d), and when the seedlings are 2cm tall (as shown Figure 3 Move the culture bottles into the greenhouse (as shown). After one day in the greenhouse, open the bottle caps, remove the seedlings with tweezers, rinse the culture medium from the roots with clean water, and transplant them into seedling trays.

[0034] (3) Seedling medium configuration and sowing Prepare the seedling tray according to the following composition: Bottom layer: peat soil: perlite = 3:1 (volume ratio), thickness 3cm.

[0035] Middle layer: 0.5-1mm vermiculite, thickness 1cm.

[0036] Surface layer: Slow-release fertilizer containing 15% total nitrogen (calculated as elemental N), 15% effective phosphorus pentoxide (P2O5), and 15% soluble potassium oxide (K2O), evenly spread 0.5 cm.

[0037] The high-vigor seeds in step (2), the medium-vigor seeds after soaking, and the low-vigor seeds obtained by tissue culture were planted in a 72-hole seedling tray, with one seed per hole. The tray was covered with vermiculite until it was completely buried, and water was sprayed until the moisture content of the substrate reached 90%.

[0038] Pest and disease control: Irrigate the roots with 1:2000 Shishile (fludioxonil), 50 mL per tray.

[0039] (4) Temperature and humidity management A small arch shed and sunshade net are built in the greenhouse to control temperature and humidity.

[0040] Germination period (1-2 days after sowing): control the temperature at 20℃±1℃, humidity at 75%, and shading rate at 50%. Figure 4 shown.

[0041] Seedling stage (emergence to 4 true leaves, such as Figure 5 Shown): Temperature 27°C, humidity 55%, 12 hours of sunlight per day (intensity 10,000 lux).

[0042] Control equipment: The greenhouse is equipped with an automatic temperature control system, a mobile sprinkler truck (nozzle fineness ≥ 1000 mesh) and a humidity sensor.

[0043] Figure 5 It shows that when there are 4 true leaves, the root system is well developed and growing strongly.

[0044] (5) Gradual stress hardening Ridges (25 cm high and 50 cm wide) were made on the seedbed with a ridge spacing of 0.5 m.

[0045] The seedlings that have emerged to 4 true leaves in step (4) are planted on the seedbed and subjected to outdoor progressive stress hardening.

[0046] The steps of progressive stress hardening are: Day 1-3: Light 6000±500lux, water once a day, substrate humidity ≥70%.

[0047] Day 4-7: Light intensity 8000±500lux, humidity reduced to 50%, and foliar spraying of 1:1000 potassium dihydrogen phosphate.

[0048] Day 8-14: natural light, intermittent watering (replenish water when humidity ≤ 30%), and spreading slow-release fertilizer granules, such as Figure 6 shown.

[0049] Pest and disease control: Spray 1:1000 propamocarb (cymoxanil hydrochloride) every week and use yellow sticky boards to trap and kill aphids.

[0050] (6) Field transplanting and management When the height of the seedlings grown in step (5) is ≥15 cm, transplanting begins.

[0051] Transplanting and land preparation: Apply 5000kg of manure and 50kg of compound fertilizer per mu, deep plowing 30-35cm, and the bed width 2m.

[0052] Planting density: plant spacing 30cm, row spacing 80cm, watering twice continuously after transplanting (7 days interval), the planting results are as follows Figure 7 shown.

[0053] Pest and disease control: Spray 1:800 imidacloprid every month to control stem-boring pests.

[0054] Figure 7 It shows that the poplar seedlings are growing healthily in the fields.

[0055] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for improving the survival rate of poplar hybrid seed seedlings, characterized in that: The steps include: (1) Seed grading: The seeds were grouped and cultured, and the germination rate of each seed group was counted. The seeds were then divided into high-vigor seeds, medium-vigor seeds, and low-vigor seeds based on the germination rate. The high-vigor seeds were sown directly, the medium-vigor seeds were soaked and then sown, and the low-vigor seeds were treated with tissue culture technology. (2) Sowing and raising seedlings: The seeds treated in step (1) were planted in seedling trays and cultured until the seedlings had 4 true leaves; (3) Progressive stress hardening: Ridge the seedbed, and then plant the seedlings grown to 4 true leaves in step (2) in the seedbed for hardening; (4) Field transplanting: When the seedlings in step (3) grow to a height of ≥15 cm, transplanting and planting begins.

2. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, wherein: In step (1), the high-vigor seeds are seeds with a germination rate greater than 85%, the medium-vigor seeds are seeds with a germination rate of 60%-85%, and the low-vigor seeds are seeds with a germination rate less than 60%.

3. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, wherein: In step (1), the tissue culture technique comprises the following steps: Soak the seeds in 75% alcohol for 1 minute, rinse with sterile water, take out the seeds, and inoculate them into MS culture medium until seedlings emerge.

4. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, wherein: In step (2), the structure of the seedling tray is: Bottom layer: peat soil: perlite volume ratio = 2-4:1-2, thickness 2-4cm; Middle layer: 0.5-1mm vermiculite, thickness 1-2cm; Surface layer: slow-release fertilizer.

5. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, wherein: In step (2), the conditions for culturing the seedlings to 4 true leaves are: During the germination period 1-2 days after sowing, control the temperature at 19-23°C, humidity at 70%-80%, and shading at 40-60%. Seedling stage from emergence to 4 true leaves: temperature 24-28℃, humidity 50-60%, daily light 10-14 hours, intensity 8000-10000 lux.

6. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, characterized in that: In step (3), the parameters of ridge formation are: ridge height 20-30 cm, ridge width 45-55 cm, and ridge spacing 0.5 m.

7. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, characterized in that: In step (3), the step of hardening the seedlings includes: Day 1-3: Light intensity 6000±500 lux, watering 1-2 times a day, substrate humidity ≥70%; Day 4-7: Light intensity 8000±500 lux, humidity reduced to 40-50%; Day 8-14: Natural light, intermittent watering, and water replenishment when humidity is ≤30%.

8. The method for improving the survival rate of poplar hybrid seed seedlings according to claim 1, characterized in that: In step (4), the planting row spacing is: plant spacing 25-30 cm, and row spacing 80-100 cm.

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