Method for overcoming distant hybridization obstacle of crape myrtle and lythrum salicaria by utilizing gibberellin

Abstract

The invention relates to a method for overcoming distant hybridization obstacle of lagerstroemia indica and lythrum salicaria by gibberellin, which comprises the following steps: castration: when lagerstroemia indica flowers do not completely bloom and loosen pollen, removing stamens on the flowers with tweezers, and sleeving the flowers with sulfuric acid paper bags for isolation; spraying a gibberellin solution, namely uniformly spraying the gibberellin solution on pistil stigmas of the crape myrtle; pollination: dipping pollen of lythrum salicaria in a cotton swab in sunny weather without strong wind, smearing the pollen on pistil stigmas of lagerstroemia indica treated by a gibberellin solution, bagging in time after pollination, and marking. The technical problem to be solved by the invention is to promote distant hybridization, fertilization and fruit setting of crape myrtle and lythrum salicaria by spraying gibberellin to stigmas before pollination, so that distant hybridization obstacles are overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of plant hybridization, and particularly relates to a method for overcoming the distant hybridization obstacle between crape myrtle and loosestrife by utilizing gibberellins. Background Art

[0002] Crape myrtle Lagerstroemia indica ) is a plant of the genus Lagerstroemia in the Lythraceae family, native to China. It is a traditional famous flower in my country and one of the most popular summer flowering tree species in garden applications. It is widely cultivated and used around the world and has extremely high economic and cultural value. Lythrum salicaria Lythrum spp., a member of the Lythrum genus of the Lythraceae family, combines ornamental value with ecological adaptability, playing a crucial role in aquatic landscape design. Lythrum spp., distributed as far north as Heilongjiang Province, China, is known for its strong cold tolerance. As a closely related genus of the genus Lagerstroemia, Lythrum spp. has the potential to serve as an important germplasm resource for improving the cold tolerance of Lagerstroemia.

[0003] Distant hybridization refers to the crossbreeding of species, genera, or even more distantly related plant groups in plant taxonomy. In the genetic improvement of ornamental plants, distant hybridization has been widely validated as an effective method for introducing genetic variation. However, due to severe reproductive barriers between distantly related species, successful hybridization often remains difficult. Sexual barriers in distant hybridization can be categorized as pre- and post-fertilization barriers. Pre-fertilization barriers refer to the inability to complete fertilization and develop a zygote. Post-fertilization barriers refer to hybrid collapse caused by incoordination between the development of the hybrid embryo and endosperm tissue, leading to embryo degradation or abortion, or hybrid sterility.

[0004] Distant hybridization between crape myrtle and loosestrife suffers from severe hybridization barriers, manifested in large numbers of flowers and fruits dropping after artificial pollination. Currently, no technology exists to overcome these barriers. Summary of the Invention

[0005] In view of this, the main purpose of the present invention is to provide a method for overcoming the barriers to distant hybridization between Lagerstroemia indica and Lythrum salicaria by utilizing gibberellins. The technical problem to be solved is to promote the fertilization and fruit setting of distant hybridization between Lagerstroemia indica and Lythrum salicaria by spraying gibberellins on the stigmas before pollination, thereby overcoming the barriers to distant hybridization.

[0006] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. The present invention proposes a method for overcoming the barrier of distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, comprising the following steps: 1) Emasculation: Before the crape myrtle flowers fully open and shed pollen, use tweezers to remove the stamens from the flowers and place them in a sulfuric acid paper bag for isolation; 2) Mist spraying gibberellin solution: spray the gibberellin solution evenly on the stigma of the pistil of the crape myrtle; 3) Pollination: On a sunny day without strong winds, use a cotton swab to dip the pollen of Lythrum salicaria and apply it to the stigma of the crape myrtle treated with gibberellin solution. After pollination, bag the flowers and mark them in time.

[0007] The objectives and technical problems solved by the present invention can be further achieved by adopting the following technical measures.

[0008] Preferably, in the aforementioned method of overcoming the barrier to distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, in step 1), the time for emasculation is 4:00 to 6:00 in the morning on a clear and windless day.

[0009] Preferably, in the aforementioned method of overcoming the barrier of distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, in step 2), the variety of Lagerstroemia indica is 'Pink Crystal' or 'Multi-Flower Purple'.

[0010] Preferably, in the aforementioned method of using gibberellins to overcome the barrier of distant hybridization between Lagerstroemia indica and Lythrum salicaria, in step 2), the concentration of the gibberellins solution is 150-250 mg·L -1 .

[0011] Preferably, in the aforementioned method of overcoming the barrier to distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, in step 2), the Lagerstroemia indica variety is 'Pink Crystal', and 250 mg·L of gibberellins is evenly sprayed on the pistil stigma of 'Pink Crystal' after emasculation and before pollination. -1 Gibberellin solution.

[0012] Preferably, in the aforementioned method of overcoming the barrier to distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, in step 2), the Lagerstroemia indica variety is 'Duohua Zi', and 200 mg·L gibberellins are evenly sprayed on the pistil stigma of 'Duohua Zi' after emasculation and before pollination. -1 Gibberellin solution.

[0013] Preferably, in the aforementioned method of using gibberellins to overcome the barrier to distant hybridization between crape myrtle and Lythrum salicaria, in step 2), the crape myrtle variety is 'Pink Crystal', and 200 mg·L gibberellins are evenly sprayed on the pistil stigma of 'Duohua Zi' after emasculation and before pollination. -1 Gibberellin solution.

[0014] Preferably, in the aforementioned method of overcoming the barrier to distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, in step 2), the Lagerstroemia indica variety is 'Duohua Zi', and 200 mg·L gibberellins are evenly sprayed on the pistil stigma of 'Duohua Zi' after emasculation and before pollination. -1 Gibberellin solution.

[0015] Preferably, in the method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin, in step 3), the pollination time is from 9:00 to 10:00 in the morning under sunny and windless weather.

[0016] Preferably, in the method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin, in step 1), the forceps are disinfected with 75% (v / v) alcohol solution.

[0017] Compared with the prior art, the method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin of the present invention has the following beneficial effects: 1. According to the present invention, the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria can be overcome conveniently and at low cost. By simply and evenly spraying 150 - 250 mg·L -1 gibberellin solution on the stigma of the pistil of Lagerstroemia indica after emasculation and before pollination, the distant hybridization between Lagerstroemia indica and Lythrum salicaria can be promoted, and the degree of affinity can be improved.

[0018] 2. According to the present invention, practical technical means can be provided for obtaining hybrid offspring of Lagerstroemia indica and Lythrum salicaria. By atomizing gibberellin solution on the stigma of the pistil of Lagerstroemia indica, the fruit setting rate can be increased. On this basis, hybrid offspring plants can be obtained by means of embryo culture or seed sowing.

[0019] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following takes the preferred embodiments of the present invention as detailed description as follows. Brief Description of the Drawings

[0020] Figure 1 are photos of Lagerstroemia indica and Lythrum salicaria in the embodiments of the present invention. Among them, A: Lagerstroemia indica 'Duohuazi'; B: Lagerstroemia indica 'Fenjing'; C: Lythrum salicaria; Figure 2 is the pollen tube growth status diagram of 'Fenjing' × Lythrum salicaria in the embodiments of the present invention; among them, a: OU: ovule; the arrow indicates the pollen tube. b: Figure 2 A - L are the growth conditions of the pollen tube after 1, 2, 4, 8, 12, 24, 48, 72 h after pollination; Figures K, L: the growth conditions of the papilla cells, style and ovary 72 h after pollination; Figure 3 is the pollen tube growth status diagram of 'Duohuazi' × Lythrum salicaria in the embodiments of the present invention; among them, a: OU: ovule; the arrow indicates the pollen tube. b: Figure 2 A - L are the growth conditions of the pollen tube after 1, 2, 4, 8, 12, 24, 48, 72 h after pollination; Figures K, L: the growth conditions of the papilla cells, style and ovary 72 h after pollination; Figure 4Flower retention of 'Pink Crystal' × Lythrum salicaria after hybridization pollination for 1 - 3 days under different concentrations of GA3 treatment in the embodiments of the present invention; a: T1 - T3: 150, 200, 250 mg·L⁻¹ GA3; CK: water; Figure 5 Fruit retention of 'Pink Crystal' × Lythrum salicaria after hybridization pollination for 4 - 31 days under different concentrations of GA3 treatment in the embodiments of the present invention; a: T1 - T3: 150, 200, 250 mg·L⁻¹ GA3; CK: water; Figure 6 Flower retention of 'Multi - flower Purple' × Lythrum salicaria after hybridization pollination for 1 - 3 days under the same concentration of GA3 treatment in the embodiments of the present invention; a: T1 - T3: 150, 200, 250 mg·L⁻¹ GA3; CK: water; Figure 7 Fruit retention of 'Multi - flower Purple' × Lythrum salicaria after hybridization pollination for 4 - 31 days under different concentrations of GA3 treatment in the embodiments of the present invention; a: T1 - T3: 150, 200, 250 mg·L⁻¹ GA3; CK: water; Figure 8 Microscopic observation diagram of paraffin sections of embryo development of 'Pink Crystal' self - pollination in the embodiments of the present invention; Note a: The red arrow indicates the zygote. a and b are the zygotes at 4 and 6 days after pollination respectively; c and d are the multicellular pro - embryos at 4 and 6 days after pollination respectively; e is the globular embryo at 16 days after pollination; f is the torpedo - shaped embryo at 14 days after pollination; g is the late cotyledon stage at 18 days after pollination; h is the mature embryo at 35 days after pollination; Figure 9 Microscopic observation diagram of paraffin sections of embryo development of 'Pink Crystal' × Lythrum salicaria hybridization in the embodiments of the present invention; Note a: a and b are the multicellular pro - embryos at 4 and 6 days after pollination respectively; c, d, e are the abnormal embryos at 8, 14, 16 days after pollination, showing the phenomena of abnormal embryo sac and empty sac; f is the mature embryo at 30 days after pollination; Figure 10 Embryo culture diagram of self - pollination and hybridization fruits of 'Pink Crystal' × Lythrum salicaria in the embodiments of the present invention; Note a: A: The fruit at 30 days after hybridization pollination treated with 250 mg·L⁻¹ GA3 solution; B, C: The hybrid embryo and self - pollinated embryo germinate 7 days after inoculation respectively; D: The fruit at 30 days after 'Pink Crystal' self - pollination; E, F: The 'Pink Crystal' self - pollinated embryo grows more roots 36 days after inoculation; Figure 11 Diagram of 'Pink Crystal' seedlings and hybrid F1 generation of 'Pink Crystal' × Lythrum salicaria in the embodiments of the present invention; Note a: (1): A - D are the hybrid F1 generations of 'Pink Crystal' × Lythrum salicaria to be identified; (2): A, B are 'Pink Crystal' seedlings. Detailed implementation manners

[0021] To further illustrate the technical means and efficacy employed by the present invention to achieve the intended purpose of the invention, the following, in conjunction with preferred embodiments, describes in detail the specific implementation, structure, features, and efficacy of a method for overcoming the barrier to distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0022] Unless otherwise specified, the materials and reagents mentioned below are all commercially available products familiar to those skilled in the art; unless otherwise specified, the methods described are all methods well known in the art. Unless otherwise defined, technical or scientific terms used should have the same meanings as those of ordinary skill in the art. Where specific experimental procedures or conditions are not specified below, the procedures or conditions described in the literature in this field can be followed.

[0023] Some embodiments of the present invention provide a method for overcoming the barrier of distant hybridization between Lagerstroemia indica and Lythrum salicaria using gibberellins, comprising the following steps: 1) Emasculation: Between 4:00 and 6:00 in the morning on a clear, windless day, before the flowers of the crape myrtle fully open and shed pollen, use tweezers to remove the stamens from the flowers and cover them with a sulfuric acid paper bag to isolate them. When removing the stamens, you need to be careful not to damage the pistils. Effect: Emasculation and bagging can prevent hybridization from being interfered with by foreign pollen and can protect the pistils.

[0024] 2) Mist spraying gibberellin solution: spray the gibberellin solution evenly on the stigma of the pistil of the crape myrtle; 3) Pollination: On a clear, windless day, use a cotton swab to dip Lythrum salicaria pollen and gently apply it to the stigma of the crape myrtle treated with the gibberellin solution. After pollination, bag the pistil and mark it. There is no limit to the amount of pollen applied, as long as the stigma is visible to the naked eye.

[0025] In some optional embodiments, in step 1), the time for emasculation is 4:00-6:00 in the morning under clear and windless weather. Too early (e.g., earlier than 4:00 in the morning) or too late (e.g., later than 6:00 in the morning) is not conducive to the smooth progress of the hybridization pollination experiment.

[0026] In some optional embodiments, in step 2), the crape myrtle variety is 'Pink Crystal' or 'Multi-Flower Purple'. The crape myrtle varieties 'Pink Crystal' and 'Multi-Flower Purple' have bright flower colors and good growth conditions, and are suitable as hybrid parents.

[0027] In some optional embodiments, in step 2), the concentration of the gibberellin solution is 150-250 mg·L -1。150 - 250 mg·L -1 Gibberellin solution is the suitable hormone to promote fertilization and fruit setting of the hybrid combination (‘Pink Crystal’ and Lythrum salicaria), and when it is lower than 150 mg·L -1 or higher than 250 mg·L -1 , the fruit setting rate will decrease.

[0028] In some alternative embodiments, in step 2), the cultivar of Lagerstroemia indica is ‘Pink Crystal’. For the hybrid combination ‘Pink Crystal’ × Lythrum salicaria, 200 mg·L -1 or 250 mg·L -1 of gibberellin solution is evenly sprayed on the pistil stigma of ‘Pink Crystal’ before pollination after emasculation. According to the experiments in specific embodiments, 250 mg·L -1 of gibberellin solution can more effectively promote fertilization and fruit setting of the hybrid combination ‘Pink Crystal’ × Lythrum salicaria.

[0029] In some alternative embodiments, in step 2), the cultivar of Lagerstroemia indica is ‘Pink Crystal’. For the hybrid combination ‘Multi-flowered Purple’ × Lythrum salicaria, 200 mg·L -1 or 250 mg·L -1 of gibberellin solution is evenly sprayed on the pistil stigma of ‘Multi-flowered Purple’ before pollination after emasculation. According to the experiments in specific embodiments, 200 mg·L -1 of gibberellin solution can more effectively promote fertilization and fruit setting of the hybrid combination ‘Multi-flowered Purple’ × Lythrum salicaria.

[0030] In some alternative embodiments, according to the hybridization research, in step 3), the time of pollination can be set at 9:00 - 10:00 in the morning on a sunny and windless day. Such a setting is beneficial to the distant hybridization between Lagerstroemia and Lawsonia.

[0031] In some alternative embodiments, the method specifically includes the following steps: 1) Emasculation is generally carried out on a sunny and windless day at 4:00 - 6:00 in the early morning when the flower buds have cracked and the petals have not yet unfolded. The forceps need to be disinfected with 75% (v / v) alcohol solution; then all stamens are removed with the disinfected forceps, and ensure that the pistil is not damaged during the emasculation process. After emasculation, choose a sulfuric acid paper bag to bag the emasculated inflorescence. Avoid squeezing the inflorescence during bagging, seal it with a paper clip, and mark the parental information and the number of emasculated flowers. The above-mentioned “the flower buds have cracked and the petals have not yet unfolded” is judged by the naked eye, that is, the flower buds are loose and the petals are curled in the flower buds and have not yet unfolded.

[0032] 2) Gibberellin solution spraying is carried out before pollination, and it is required to be evenly sprayed, and at the same time, it is necessary to ensure that the branches and leaves of other parts will not be affected by exogenous hormones. For the hybrid combination ‘Pink Crystal’ × Lythrum salicaria, 250 mg·L -1Gibberellin solution, and for the hybrid combination 'Duohua Purple' × Lythrum salicaria, 200 mg·L -1 gibberellin solution is used; such setting can promote the fertilization and fruit setting of the female parent in hybridization.

[0033] 3) Pollination is generally carried out on a sunny and windless day, and the time is from 8:00 to 10:00 in the morning. When the flowers are in the full-bloom stage and the stigma secretes a large amount of mucus, after atomizing the gibberellin solution on the stigma, pollination is carried out immediately. Dip a cotton swab in pollen and gently smear it on the pistil stigma of Lythrum salicaria. After pollination, bag it in time and make good marks.

[0034] In the above technical solution, the present invention sprays gibberellin solution on the stigma of Lagerstroemia indica after emasculation and then conducts pollination, which can significantly improve the phenomenon of flower and fruit dropping, and overcome the obstacle of distant hybridization to a certain extent.

[0035] The following will further illustrate the present invention in conjunction with specific embodiments, but it cannot be understood as a limitation to the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention according to the above content of the present invention still fall within the protection scope of the present invention.

[0036] Example 1 This example provides a method for overcoming the distant hybridization obstacle between Lagerstroemia indica and Lythrum salicaria by using gibberellin, including the following steps: 1) Emasculation: It is carried out on a sunny and windless day, and emasculation is carried out for one and a half hours from 4:30 to 6:00 in the morning. Select the Lagerstroemia indica variety 'Pink Crystal', the flower bud shows a cracked state, the flower bud is loose, and the petals are curled in the flower bud and still not unfolded. Use tweezers disinfected with 75% (v / v) alcohol solution to remove all stamens, and ensure that the pistil is not damaged during the emasculation process. After emasculation, select a kraft paper bag with a size of about 26*17 cm to bag the emasculated inflorescence. Avoid squeezing the inflorescence during bagging, seal it with a paper clip, and mark the information of the male and female parents and the emasculation quantity on the surface of the paper bag with a pencil.

[0037] 2) Atomize gibberellin solution: Uniformly spray the gibberellin solution of 250 mg·L -1 on the pistil stigma of Lagerstroemia indica 'Pink Crystal'; 3) Pollination: When it is sunny and there is no strong wind, dip a cotton swab in the pollen of Lythrum salicaria and gently smear it on the pistil stigma of Lagerstroemia indica treated with gibberellin solution. After pollination, bag it in time and make good marks.

[0038] Pollinate 100 flowers and conduct three repeated experiments. Record the flower dropping situation every day within 1 to 3 days after pollination, record the fruit dropping situation every day within 4 to 7 days after pollination, and record and count every three days after one week until one month after pollination. The flower and fruit dropping situation is shown in Table 1.

[0039] Example 2 The difference between this example and Example 1 is that the concentration of the gibberellin solution in this example is 200 mg·L -1 ; the remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0040] Example 3 The difference between this example and Example 1 is that the concentration of the gibberellin solution in this example is 150 mg·L -1 ; the remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0041] Example 4 The difference between this example and Example 1 is that the Lagerstroemia indica variety in this example is 'Duohua Zi'; the remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 2.

[0042] Example 5 The difference between this example and Example 4 is that the concentration of the gibberellin solution in this example is 200 mg·L -1 ; the remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0043] Example 6 The difference between this example and Example 4 is that the concentration of the gibberellin solution in this example is 150 mg·L -1 ; the remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that the concentration of the gibberellin solution in this comparative example is 0. The remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example uses a 6-BA solution with a concentration of 20 mg·L -1 ; the remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example uses a 6-BA solution with a concentration of 30 mg·L -1 ; the remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0047] Comparative Example 4 The difference between this comparative example and Example 1 is that this comparative example uses a 6-BA solution with a concentration of 40 mg·L -1; The remaining steps and parameters are the same as those in Example 1. The flower and fruit drop situation is shown in Table 1.

[0048] Comparative Example 5 The difference between this comparative example and Example 4 is that the concentration of the gibberellin solution in this comparative example is 0. The remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0049] Comparative Example 6 The difference between this comparative example and Example 4 is that this comparative example uses a 6-BA solution with a concentration of 20 mg·L -1 ; The remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0050] Comparative Example 7 The difference between this comparative example and Example 4 is that this comparative example uses a 6-BA solution with a concentration of 30 mg·L -1 ; The remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0051] Comparative Example 8 The difference between this comparative example and Example 4 is that this comparative example uses a 6-BA solution with a concentration of 40 mg·L -1 ; The remaining steps and parameters are the same as those in Example 4. The flower and fruit drop situation is shown in Table 2.

[0052] Table 1 Statistics of the average retention of flowers and fruits of Lagerstroemia indica 'Pink Crystal' under different treatments Table 2 Statistics of the average retention of flowers and fruits of Lagerstroemia indica 'Flore Pleno' under different treatments By comparing the examples and comparative examples, it can be found that in Comparative Examples 1 and 4, the concentration of the gibberellin solution is 0, and for the Lagerstroemia indica varieties 'Pink Crystal' and 'Flore Pleno', 3 days and 5 days after pollination respectively, the flowers together with the ovaries all dropped. In Examples 1 - 6, by spraying 150 - 250 mg·L -1 of gibberellin before pollination, the phenomenon of flower and fruit drop can be improved to varying degrees. Comparing the examples with the comparative examples, for 'Pink Crystal', the gibberellin solution with a concentration of 250 mg·L -1 has the relatively best improvement effect, and the fruit setting rate can reach 78.33% 31 days after pollination; while for 'Flore Pleno', the gibberellin solution with a concentration of 200 mg·L -1 has the relatively best improvement effect, and the fruit setting rate can reach 59.33% 31 days after pollination.

[0053] Specific Application Example 1 Artificial assisted pollination was carried out for the distant hybridization of Lagerstroemia indica and Lythrum salicaria in the Sanqingyuan of Beijing Forestry University from July to August 2024. The materials are as Figure 1 shown.

[0054] By observing the pollen tubes after pollination without being sprayed with GA3 solution under fluorescence microscopy, whether using 'Fen Jing' or 'Duohua Zi' as the female parent, it was found that only a very small number of pollen tubes entered the ovary or ovules, and at the same time, there was a large amount of flower and fruit drop. The growth status of the pollen tubes is as Figure 2 , 3 shown. From Figure 2 , [[ID= , it can be seen that 72 h after pollination, a large amount of callose still accumulated at the connection between the papilla cells and the style and even at the upper end of the style, and very few pollen tubes were observed in the ovary.

[0055] Select sunny and windless weather for artificial assisted pollination. From 4:00 to 6:00 in the morning, the flower buds were in a state of having cracked, but the petals had not yet unfolded. Use tweezers disinfected with 75% (v / v) alcohol solution to emasculate the flowers and cover them with sulfuric acid paper bags to prevent contamination by foreign pollen.

[0056] At 8:00 - 10:00 in the morning, the flowers were in full bloom and the stigmas secreted a large amount of mucus. Remove the sulfuric acid paper bags and spray GA3 solution on the stigmas of the pistils of 'Fen Jing' and 'Duohua Zi' respectively. Then dip a cotton swab in pollen and gently smear it on the stigmas of the pistils of 'Fen Jing' and 'Duohua Zi'. Immediately after pollination, bag them and make good marks.

[0057] For the 'Fen Jing' × Lythrum salicaria hybrid combination, on the 3rd day after pollination, all the flowers sprayed with clear water (CK group) fell off ( ​ ). Compared with the GA3 solutions of 150 and 200 mg·L -1 , the GA3 solution of 250 mg·L -1 had relatively appropriate flower and fruit retention effects. On the 3rd day after pollination, the flower retention rate was 96.67% ( ​ ), and the fruit setting rate reached 78.33% on the 31st day after pollination ( ​ ).

[0058] For the 'Duohua Zi' × Lythrum salicaria hybrid combination, on the 5th day after pollination, all the flowers sprayed with clear water (CK group) fell off ( ​ ). Compared with the GA3 solutions of 150 and 250 mg·L -1 , the GA3 solution of 200 mg·L -1 had relatively appropriate flower and fruit retention effects. On the 3rd day after pollination, the flower retention rate was 97.43% ( ​ ), and the fruit setting rate reached 59.33% on the 31st day after pollination ( ​ ).

[0059] Specific Application Example 2 In the hybrid combination 'Pink Crystal' × Lythrum salicaria, 250 mg·L -1 solution was sprayed on the pistil stigma to promote fertilization and fruit setting. Through paraffin section microscopic observation and comparison of the fruit development status of 'Pink Crystal' self-cross and 'Pink Crystal' × Lythrum salicaria cross, it was found that 250 mg·L -1 solution could promote the development of hybrid fruits to a certain extent and overcome the hybridization barrier between 'Pink Crystal' and Lythrum salicaria ( ​ , 9 ).

[0060] The development process of the self-cross fruit of 'Pink Crystal' was that the zygote began to divide 2 and 4 days after pollination ( ​ .a), multicellular proembryos appeared 4 and 6 days after pollination ( ​ .c, d), the embryo entered the globular embryo stage 10 days after pollination ( ​ .e). Since the embryo development in the same ovary may not be synchronous, torpedo-shaped embryos could be observed as early as 14 days after pollination ( ​ .f). Therefore, 10 - 16 days after pollination, the embryo development may be in the globular embryo, torpedo-shaped embryo, or the process of transformation from the globular embryo to the torpedo-shaped embryo. 18 days after pollination, an embryo in the cotyledon stage could be observed and was already relatively mature ( ​ .g). Mature late-stage embryos could be observed 30 days after pollination ( ​ .h).

[0061] Similar to the self-cross embryo, multicellular proembryos were observed 4 and 6 days after pollination in the distant hybrid fruit of 'Pink Crystal' × Lythrum salicaria (see ​ .a, ​ .b), but 8, 14, and 16 days after pollination (see ​ .c, ​ .d, ​ .e), further development of multicellular proembryos was not observed. Instead, the phenomenon of abnormal embryo sac and empty sac occurred. However, 30 days after cross-pollination, mature embryos were observed (see ​ .f). This shows that although most of the section tissues may start to abort 6 days after pollination, due to spraying 250 mg·L -1 GA3 solution, a small number of embryos can develop normally to maturity.

[0062] Specific Application Example 3 Embryo culture was carried out on the self-cross and hybrid fruits of 'Pink Crystal' × Lythrum salicaria that were pollinated 30 - 35 days after being treated with 250 mg·L -1 GA3 solution by fog spraying (see ​ .A, ​. D). Seven days after inoculation, both hybrid and self-cross embryos developed young roots and cotyledons (see ​ . B, ​ . C). Due to the occurrence of medium contamination, when the young roots grew to about 1 cm, both self-crossed seedlings and hybrid seedlings were transplanted into square pots for maintenance, and a total of 4 hybrid F1 generations to be identified were obtained (see ​ ). This shows that the 250 mg·L -1 GA3 solution not only has a certain fruit retention effect, but also can promote the growth and development of embryos.

[0063] In the description of the present invention, a large number of specific details are set forth. However, it is understood that the embodiments of the present invention may be practiced without these specific details. In some embodiments, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0064] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination manners.

[0065] Furthermore, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

[0066] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria using gibberellin, characterized in that, It includes the following steps: 1) Emasculation: When the Lagerstroemia indica flowers have not fully opened and shed pollen, use forceps to remove all the stamens on the flowers and cover them with sulfuric acid paper bags for isolation; 2) Atomizing gibberellin solution: Evenly spray the gibberellin solution on the stigma of the pistil of Lagerstroemia indica; 3) Pollination: On a sunny and windless day, dip a cotton swab in the pollen of Lythrum salicaria and smear it on the stigma of the pistil of Lagerstroemia indica treated with gibberellin solution. Immediately after pollination, bag it and make good marks.

2. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin according to claim 1, wherein, In step 1), the time for emasculation is from 4:00 to 6:00 in the early morning under sunny and windless weather.

3. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin as claimed in claim 1, wherein In step 2), the variety of Lagerstroemia indica is 'Pink Crystal' or 'Multiflora Purple'.

4. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria using gibberellin according to claim 3, characterized in that, In step 2), the concentration of the gibberellin solution is 150 - 250 mg·L -1 .

5. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin as claimed in claim 4, wherein In step 2), the variety of Lagerstroemia indica is 'Pink Crystal'. Before pollination after emasculation, the pistil stigmas of 'Pink Crystal' are evenly sprayed with 250 mg·L -1 gibberellin solution.

6. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin according to claim 4, wherein In step 2), the cultivar of Lagerstroemia indica is 'Duohua Zi'. Before pollination after emasculation, the pistil stigmas of 'Fen Jing' are evenly sprayed with 250 mg·L -1 gibberellin solution.

7. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin according to claim 4, characterized in that, In step 2), the variety of Lagerstroemia indica is 'Pink Crystal'. Before pollination after emasculation, the pistil stigmas of 'Multiflora Purple' are evenly sprayed with 200 mg·L -1 gibberellin solution.

8. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin according to claim 4, characterized in that, In step 2), the cultivar of Lagerstroemia indica is 'Duohua Zi', and 200 mg·L -1 gibberellin solution is evenly sprayed on the pistil stigma of 'Duohua Zi' before pollination after emasculation.

9. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin according to claim 1, characterized in that In step 3), the time for pollination is from 9:00 to 10:00 in the morning under sunny and windless weather.

10. The method for overcoming the distant hybridization barrier between Lagerstroemia indica and Lythrum salicaria by using gibberellin as claimed in claim 1, characterized in that, In step 1), the forceps are disinfected with 75% (v / v) alcohol solution.

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