A method for increasing the water resistance and yield of oil-growing peonies.

Abstract

This invention provides a method to improve the water resistance of oil-producing peonies and to increase their production. [Solution] Using the oil-growing peony variety FD as the mother plant, select and cross the father plants DFG, YLC, YPH, and HFR, each with different affinity, to obtain the following hybrid combinations: (1) Close affinity: DFG × FD; (2) Moderate affinity: YLC × FD; (3) Distant affinity: YPH × FD; (4) Distant affinity: HFR × FD. Furthermore, this method also includes a step of using coronatin to replace hydrophilic seed immersion during seed germination. This method was found to significantly improve the water resistance of oil-growing peonies and also improve yield.

Description

Technical Field

[0001] The present invention relates to a method for enhancing the water tolerance of Paeonia ostii and simultaneously increasing the yield, and particularly relates to a method for improving the water tolerance of Paeonia ostii through hybridization and seed immersion with coronatin.

Background Art

[0002] "Fengdan" is a variety of Paeonia ostii mainly cultivated in the southern region of China and has attracted attention as a new woody oil crop. It has characteristics such as drought tolerance, adaptability to poor soil, cold tolerance, and shade tolerance. However, its root system is a fleshy root and is sensitive to water, so it is classified as a plant with low water tolerance. In the southern region, due to the large amount of precipitation, waterlogging often occurs, which has a great impact on the yield of "Fengdan". Every year, the yield of "Fengdan" decreases by more than 40% due to precipitation. Especially in the southern region of China, since the pod formation period of "Fengdan" overlaps with the plum rain season, diseases may occur due to the roots being immersed in water for a long time, and in some cases, they may even rot. On the above-ground part, phenomena such as yellowing or blackening of the leaves and mold growth on the immature fruit pods can be observed. Therefore, as a fundamental solution, it is urgent to select Paeonia ostii varieties with high water tolerance and solve the problem of yield reduction due to insufficient water tolerance at the variety level. Breeding new "Fengdan" varieties with good water tolerance through cross-breeding and introducing them into production has very important significance for the development of the peony industry.

[0003] Hybrid breeding is a traditional breeding method that is easy to perform and effective, and is still used as a primary method for developing new varieties. To date, many researchers have obtained new peony genetic resources through crossbreeding oil-producing peonies with ornamental peonies. The main breeding goals are focused on improving ornamental value, strengthening tolerance to adverse conditions, and developing varieties for specific uses such as cut flowers, bonsai, and oil production. Regarding breeding directions for strengthening tolerance to adverse conditions, heat tolerance, cold tolerance, drought tolerance, salt tolerance, heavy metal tolerance, and disease and pest resistance are the main focus, with very few reports targeting water tolerance as a breeding goal, and water tolerance evaluations are limited to those between peony varieties. Crossing varieties with strong water tolerance with varieties with weak water tolerance is the most effective and reliable method for improving the water tolerance of varieties with weak water tolerance. However, no inventions for creating water-tolerant genetic resources for 'Hōtan' have been reported domestically or internationally, and highly water-tolerant oil-producing peony varieties are desperately needed in the production field.

[0004] This invention involves interspecific crosses between different ornamental peony varieties from the Jiangnan region of China and "Fengdan," verifying the fruiting rate and germination rate of the hybrid seeds in different cross combinations, and conducting immersion tests on the hybrid progeny and parent seedlings. By measuring the morphological and physiological indicators of the seedlings, hybrid progeny with superior water resistance are selected. The new water-resistant "Fengdan" varieties obtained by this invention provide a variety resource, especially in southern regions with high rainfall, particularly the Jiangnan region of China, solving a fundamental problem in "Fengdan" production and providing a favorable resource guarantee for the development of the oil peony industry.

[0005] Coronatin (COR) is a compound isolated from a pseudomonospheric fungus derived from lilac. It has a chemical structure similar to jasmonic acid compounds (JAs) and shares many similar physiological functions. Studies have shown that COR has various physiological functions, including regulating plant growth and development, inducing related secondary metabolites, and enhancing plants' tolerance to environmental stress (Xu Ruqiang, 1998; Ai Lin, 2008). For example, Qi Fuguo et al. (2006) reported that COR treatment under low-temperature conditions increased the soluble protein content and decreased relative conductivity and MDA (malondialdehyde) content in wheat leaves. Ai Lin et al. (2008) found that COR treatment under drought conditions maintained the relative water content of rice leaves, promoted the accumulation of soluble proteins, reduced cell membrane permeability, and maintained cell membrane integrity.

[0006] Patent document CN201810769231 discloses a breeding method to improve the drought tolerance of oil-producing peony. In this method, an oil-producing peony variety with superior traits is selected as the mother plant, and a variety with stable yield is selected as the father plant. They are crossbred to harvest F1 seeds, cultivated, and harvested together to obtain F2 seeds. The F2 individuals are crossbred with the mother plant to obtain BC1 seeds, and the BC1 individuals are crossbred with the mother plant again to obtain BC2 seeds. Finally, the BC2 seeds are planted, self-pollination is carried out for 3-4 generations, and the best line is selected to become a new oil-producing peony variety. During this process, a stress agent is used to treat the plants with water stress, suppressing the germination of seeds that are not drought-tolerant. This reduces the occurrence of false-positive drought-tolerant seeds, reduces the total sample size for crossbreeding, reduces the workload, and improves breeding efficiency.

[0007] Patent document CN202010947381 discloses a method for improving the drought resistance of oil-growing peonies using methyl jasmonate. Specifically, the method involves spraying methyl jasmonate onto the leaves of oil-growing peonies during cultivation. This method significantly increases the net photosynthetic rate of the leaves, reduces damage to the peonies due to drought stress, and enhances the peonies' resistance to drought stress. However, the above-mentioned conventional technology still does not solve the problem of water resistance in oil-growing peonies. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] China Patent Publication CN201810769231 [Patent Document 2] China Patent Publication CN202010947381 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In view of the above problems, the technical problem that the present invention aims to solve is to provide a method for developing a new water-resistant peony variety for oil production, improving the water resistance of the new variety, and increasing its yield. [Means for solving the problem]

[0010] This invention provides a method for improving the water resistance of oil-growing peonies and increasing their yield, and includes the following steps. Using the oil-producing peony variety "Houtan" FD as the mother plant, we selected and crossed sire plants DFG, YLC, YPH, and HFR, each with different affinity, to obtain the following cross combinations.

[0011] (1) Close affinity: DFG × FD (2) Moderate affinity: YLC × FD (3) Distant affinity: YPH×FD (4) Poor affinity: HFR × FD The method of the present invention further includes an alternative treatment to hydrophilic immersion using coronatin during seed germination.

[0012] The coronatin concentration mentioned above should be 0.1 μmol / L to 0.5 μmol / L. The present invention also provides the use of coronatin to improve the water resistance of oil-grown peonies, with a coronatin concentration of 0.1 μmol / L to 0.5 μmol / L. [Effects of the Invention]

[0013] The new variety of Paeonia ostii obtained by the method of the present invention shows water tolerance during the rainy season and maintains a high yield even during fruiting.

Brief Description of the Drawings

[0014] [Figure 1] Phenotypic changes of Paeonia ostii in waterlogging treatment (from left to right: FD Fengdan seedlings, hybrid progeny of YPH×FD, hybrid progeny of YLC×FD). [Figure 2] Measurement results of sucrose synthase (SS), a physiological index of Paeonia ostii hybrid progeny under waterlogging stress. Different lowercase letters on the short grids indicate statistically significant differences at the P<0.05 level among different plants within the same treatment time (n = 3, the same below). [Figure 3] Measurement results of plant α - amylase, a physiological index of Paeonia ostii hybrid progeny under waterlogging stress. [Figure 4] Measurement results of plant alcohol dehydrogenase (ADH), a physiological index of Paeonia ostii hybrid progeny under waterlogging stress. [Figure 5] Measurement results of plant pyruvate decarboxylase (PDC), a physiological index of Paeonia ostii hybrid progeny under waterlogging stress. [Figure 6] Measurement results of plant soluble protein (s - protein), a physiological index of Paeonia ostii hybrid progeny under waterlogging stress.

Modes for Carrying Out the Invention

[0015] Hereinafter, the present invention will be further described based on specific examples. Coronatine (hereinafter abbreviated as "COR") is a compound isolated from the culture broth of Pseudomonas syringae pv. Atropurpurea in 1977 and is known to cause disseminated chlorosis in many plants.

[0016] COR is structurally and functionally similar to jasmonic acid (JA), with a molecular formula of C18H25NO4 and a molecular weight of 319.4 Da. COR consists of coronamic acid (CMA) containing α - amino acids and coronafacic acid (CFA) with a polyketone structure linked by an amide bond. As shown in Chemical Formula 1, it has an alkane structure similar to methyl jasmonate (hereinafter abbreviated as "JA - Me"). Also, the activity of COR is much higher than that of JA. COR stimulates the secondary metabolism of plants, promotes the production of various phytotoxins, and is involved in regulation under stress. Its mode of action is similar to that of JA. According to an invention, both JA and COR have the effect of improving the drought tolerance of sorghum seedlings, and it has been shown that COR has a higher effect than JA. There is a certain dose - effect in the regulatory effect of COR. It is known that at low concentrations, it promotes plant growth, and at high concentrations, it inhibits growth.

[0017] The structural formula of coronatin is as follows. Chemical Formula 1 JPEG2026067328000002.jpg4999

[0018] The coronatin in the present invention can be obtained by industrial fermentation production (for example, ZL200510011466.2; ZL200510085280.1; ZL200710099033.6; ZL200810119153.2). It can also be directly purchased from chemical manufacturers. For example, the product with the product number C8115 of Sigma can be used and stored in a freezer at - 20°C. Before use, prepare a 1 mmol / L solution with double - distilled water and dilute it with tap water or field water during use.

[0019] The concentration of coronatin used in the present invention is appropriately 0.05 - 1 μmol / L, and the concentration that gives particularly excellent effects is 0.1 - 0.5 μmol / L.

[0020] Examples 1. Materials and Methods 1.1 Test Materials The test material "Fengdan" (hereinafter FD) is a 10-year-old seedling introduced from Tongling City, Anhui Province. The ornamental peonies "Yipinhong" (hereinafter YPH), "Yulouchun" (hereinafter YLC), "Hongfurong" (hereinafter HFR), and "Dafugui" (hereinafter DFG) from the Jiangnan region of China are varieties cultivated in Zhejiang Province, China, with flower colors ranging from pink to red, and flower shapes including chrysanthemum, crown, and pavilion types.

[0021] 1.2 Crossbreeding combinations Based on the compatibility of peony varieties in the Jiangnan region of China, the following hybrid combinations were selected. The main combinations are as follows:

[0022] (1) Close affinity: DFG × FD (2) Moderate affinity: YLC × FD (3) Distant affinity: YPH×FD, HFR×FD

[0023] 1.3 Method The process is carried out between 9:00 AM and 11:00 AM on a sunny day. At the end of March, select a mother plant in the early flowering stage, 1-2 days before blooming, when the flower buds are beginning to show color and the petals are just starting to open. Remove the stamens and cover with a bag. In early April, when the stamens of the father plant have matured and pollen is being dispersed, collect the pollen with tweezers and place it in a test tube with a desiccant. Take a small amount of pollen with a cotton swab and apply it to the stigma of the mother plant from which the stamens have already been removed to perform artificial pollination. After pollination, cover with a bag again and secure the bottom with a clip to prevent pollination by insects. Seven days after artificial pollination, remove the bag and expose to natural light. Harvest the pods between July 30th and August 5th when they change from green to crab yellow. Dry the harvested pods in a dark, well-ventilated place indoors for about a week, and after they have completely split open, manually remove the seeds. The number, weight, and fruit set rate (number of fruit pods / number of pollinations per 100) of seeds are statistically recorded. The extracted seeds are soaked in water for 24 hours before sowing, and the number of germinated seeds for each combination is recorded to calculate the germination rate (number of germinated seeds / number of seeds sown per 100).

[0024] Furthermore, to confirm whether seed immersion with different concentrations of methyl jasmonate and coronatin could induce water resistance, water immersion was replaced with different concentrations of methyl jasmonate or coronatin. The concentrations of methyl jasmonate and coronatin were 0.1 μmol / L, 0.5 μmol / L, and 1.0 μmol / L, and the test subjects were YLC×FD.

[0025] 1.4 Analysis of water resistance Seeds from hybrid progeny with robust seed development and their parent plants are selected and sown in 90mm size two-color pots. When the seedlings have developed two leaves, they are transplanted, with one plant per pot, and cultivated outdoors for two months. After that, seedlings with uniform growth are selected and a water immersion test is conducted. The potted seedlings are placed in a water tank, and water is poured in until the soil is submerged to a depth of 2 cm, and observed continuously for one week. Morphological indicators such as plant height, root system length, and root cap ratio are investigated, and the relative chlorophyll content is measured. In addition, the uppermost leaves are collected as test material and used to measure physiological indicators related to water damage stress (activities of sucrose synthase (SS), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), and α-amylase (RAMY), and soluble protein (PRO) content). Finally, all data are compiled, the water resistance of the hybrid progeny and parent plants is comprehensively evaluated, and hybrid progeny with strong water resistance are selected.

[0026] 1.5 Methods for measuring the above enzymes and proteins Sucrose synthase (SS): Measured using the sucrose synthase ELISA detection reagent kit from Jianglai Biotechnology Co., Ltd.

[0027] Pyruvate decarboxylase (PDC): Measured using the plant pyruvate decarboxylase ELISA detection reagent kit from Jianglai Biotechnology Co., Ltd.

[0028] Alcohol dehydrogenase (ADH): Measured using the plant alcohol dehydrogenase ELISA detection reagent kit from Jianglai Biotechnology Co., Ltd.

[0029] α-Amylase (RAMY): Measured using the plant α-amylase ELISA detection reagent kit from Jianglai Biotechnology Co., Ltd.

[0030] Soluble proteins (s-proteins): Measured using the plant soluble protein ELISA detection reagent kit from Jianglai Biotechnology Co., Ltd.

[0031] 1.6 Method for measuring relative chlorophyll content The measurement is performed using the JC-YLC chlorophyll analyzer.

[0032] 2. Results and Analysis 2.1 Fruiting status of different hybrid combinations To understand the fruiting status of different hybrid combinations, the number of fruits (fruit capsules) and seeds harvested from each combination were investigated, and the fruiting rate was calculated by combining this with the number of pollinations. The fruiting rates for all four hybrid combinations were 70% or higher, with the YLC×FD combination being the highest, reaching 85%. This was followed by the HFR×FD, YPH×FD, and DFG×FD combinations, which showed fruiting rates of 75%, 71.66%, and 70%, respectively. The seeds obtained from each combination were weighed, and the seed weight per seed was calculated based on the number of seeds. As shown in Table 1, the single seed weights of the seeds obtained from all four hybrid combinations were in the range of 443.3 to 464.7 mg, and no significant differences were observed.

[0033] Table 1: Fruit production status of different hybrid combinations JPEG2026067328000003.jpg32116

[0034] 2.2 Seed germination status of different hybrid combinations To further clarify the seed germination status of different hybrid combinations, 150 seeds of uniform size and quality were selected from the seeds obtained from each hybrid combination, and their germination status was statistically analyzed after sowing. As can be seen from Table 2, there were clear differences in seed germination status among the different hybrid combinations. The highest germination rate was observed in the YLC×FD combination, followed by the YPH×FD combination. The lowest germination rates were observed in the DFG×FD and HFR×FD combinations, with germination rates of 80.00%, 78.67%, 60.00%, and 59.33%, respectively. Overall, all four hybrid combinations had high germination rates, all above 59%.

[0035] Seed immersion treatment with different concentrations of methyl jasmonate and coronatin had a slight effect on the germination rate of YLC×FD; specifically, 1.0 μmol / L of methyl jasmonate and coronatin reduced the germination rate.

[0036] Table 2 Seed germination rates of different hybrid combinations JPEG2026067328000004.jpg28116

[0037] Table 3. Germination rates of YLC×FD seeds after immersion treatment with different solutions. JPEG2026067328000005.jpg34116

[0038] 2.3 Water resistance of hybrid offspring Based on the results of the 2.2 test, two hybrid combinations with high germination rates, YPH×FD and YLC×FD, were selected, and the water tolerance of the hybrid progeny was further investigated using groups (shown in Table 3) that were soaked in six different concentrations of methyl jasmonate and coronatin. Uncrossed 'Houtan' was used as the maternal control, and observations were made in terms of phenotypic, morphological, and physiological aspects. After continuing observations for one week, the following results were obtained.

[0039] 2.3.1 Phenotypic Characteristics From an external perspective, the leaves of the control 'Houtan' seedlings were relatively thin and pale in color. On the other hand, the hybrid seedlings obtained from the hybrid combinations YPH×FD and YLC×FD had thicker leaves and darker in color. When the phenotypic changes were observed one week after flood treatment, as shown in Figure 1, the control leaves showed mild wilting and drooping, but the hybrid seedlings obtained from the hybridization were normal, with flat leaves and no symptoms of wilting.

[0040] Furthermore, YLC×FD hybrid seedlings soaked in six different concentrations of methyl jasmonate and coronatin (shown in Table 3) showed no differences in any of the groups; the leaves were flattened and no symptoms of wilting were observed (not shown).

[0041] 2.3.2 Measurement results of morphological indicators Flood damage treatment was applied to hybrid and control seedlings, and their morphological indicators were investigated. Comparing the flood-treated group with the untreated control group, there was no change in plant height in the flood-treated group, but the plant height of the untreated control group increased by approximately 0.2-0.3 cm. After flood damage treatment, the relative chlorophyll content of the leaves decreased by 8.1% in 'Houtan', while it increased by 12.5% ​​and 0.38% in YPH×FD and YLC×FD, respectively. Root system length and root cap ratio were significantly lower in the flood-treated group than in the control group; root system length decreased by 27.08% and 24.42% in YPH×FD and YLC×FD, respectively, and root cap ratio decreased by 13.33% and 21.08%, respectively.

[0042] Comparing hybrid seedlings with control seedlings, plant height, root system length, and root cap ratio were all affected by flood treatment, with growth halted and both root system length and root cap ratio showing a decreasing trend. In contrast, the relative chlorophyll content increased in hybrid seedlings and decreased in control seedlings. The decrease in root cap ratio was smaller in hybrid seedlings (13-21%) than in control seedlings (31.88%).

[0043] Furthermore, in YLC×FD hybrid seedlings soaked in six different concentrations of methyl jasmonate and coronatin (shown in Table 3), the relative chlorophyll content increased significantly in the 0.5 μmol / L coronatin treatment group, and the decrease in root cap ratio was also remarkable in this group. Specific figures are shown in Table 5.

[0044] Table 4 Measurement of morphological indicators in flood damage treatment of peony hybrid progeny JPEG2026067328000006.jpg43116

[0045] Table 5 Measurement of morphological indicators of flood treatment in different soaking groups of peony hybrid YLC×FD JPEG2026067328000007.jpg44115

[0046] 2.3.3 Measurement results of physiological indicators Using FD as a control, we measured sucrose synthase (SS), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), α-amylase (RAMY), and soluble protein (PRO), which are physiological indicators related to flood resistance, to clarify the water resistance of hybrid progeny obtained from different hybrid combinations. As can be seen from Figure 3, when no flood treatment is performed, the sucrose synthase (SS) activity of FD, YPH×FD, and YLC×FD is almost the same. As the flood treatment time (0-7 days) is extended, the SS activity of the three combinations first increases, then decreases, reaching the highest level on the 5th day of flood treatment. In the first 3 days of flood treatment, the SS activity of the hybrid combination YLC×FD is clearly higher than that of the control FD. By the 5th day, there is no difference among the three combinations, but on the 7th day, the SS activity of the hybrid combinations YPH×FD and YLC×FD is significantly higher than that of the control FD.

[0047] As can be seen in Figure 4, when no flood treatment is performed, the α-amylase (RAMY) activity of the hybrid combinations YPH×FD and YLC×FD is significantly higher than that of the control FD. As the flood treatment time (0-7 days) is extended, the RAMY activity of the three combinations tends to increase first, and then decrease. The hybrid combination YLC×FD reaches its peak level on the third day of flood treatment, while YPH×FD and the control FD reach their peak levels on the fifth day of flood treatment. The control FD shows a sharp increase in RAMY activity one day after flood treatment, and the magnitude of this change is greater than that of the hybrid combinations YPH×FD and YLC×FD. During the flood treatment period, the RAMY activity of the hybrid combination YPH×FD is almost the same as that of the control FD, but the RAMY activity of YLC×FD is significantly higher than that of the control FD on the 0th, 3rd, and 7th days of flood treatment.

[0048] As can be seen in Figure 5, when no flood treatment is performed, the alcohol dehydrogenase (ADH) activity of the hybrid combinations YPH×FD and YLC×FD is significantly lower than that of the control FD, with YLC×FD showing the lowest activity. As the flood treatment time (0-7 days) is extended, the ADH activity of the control FD increases, then tends to decrease, reaching its highest level on day 5. The ADH activity of YPH×FD continues to increase until day 7, showing significantly higher ADH activity than both YPH×FD and the control FD on day 7. At all treatment times, the ADH activity of YPH×FD is significantly lower than that of the control FD.

[0049] As shown in Figure 6, without flood treatment, pyruvate decarboxylase (PDC) activity in YPH×FD and YLC×FD is significantly lower than that of control FD. With increasing flood treatment time (0-7 days), PDC activity in control FD initially increases, then tends to decrease, reaching its peak level on day 5. In YPH×FD and YLC×FD, it initially increases rapidly, then increases gradually, reaching its peak level on day 7. During the flood treatment period, PDC activity in YPH×FD and YLC×FD is significantly higher than that of control FD, and there is little difference between the two hybrid combinations.

[0050] As shown in Figure 7, in the absence of flood treatment, the soluble protein (PRO) content of YPH×FD and YLC×FD is significantly higher than that of the control FD. As the flood treatment time (0-7 days) is extended, the PRO content of the three combinations initially increases, then tends to decrease, reaching its highest level on day 5. One day after flood treatment, the PRO content of YPH×FD and the control FD increases rapidly, becoming higher than that of YLC×FD. The PRO content of YLC×FD increases rapidly during days 1-3 of flood treatment, becoming almost equivalent to that of YPH×FD and significantly higher than that of the control FD. On days 5 and 7, the PRO content of YPH×FD is significantly higher than that of YLC×FD.

[0051] 2.4 Fruit yield of hybrid offspring The 11 seedlings shown in Table 5 were obtained by propagating by division and transplanted to the experimental field of the Zhejiang Provincial Institute of Horticultural Plants and Floriculture in March of the third year. The spacing between plants was set at 60 cm and the spacing between rows at 100 cm. Otherwise, fertilization and weeding were carried out according to normal field management and pest and disease control methods. Harvesting took place in October of the same year when the fruit pods changed from green to yellow and split open. After harvesting, the seeds were quickly threshed and dried, maintaining a moisture content of 10% to 12%. The harvested seeds were weighed and converted to calculate the yield per mound. The results are shown in Table 6.

[0052] Table 6 Fruit yield of oil-producing peonies JPEG2026067328000008.jpg94116

[0053] In peony varieties from different sources, no phenomenon of cross-incompatibility was observed in crosses between Zhongyuan Peony and Fengdan, Japanese Peony and Fengdan, or Jiangnan Peony and Fengdan. However, there were clear differences in the characteristics of the hybrid progeny obtained by crossing different varieties. The results of this invention show that while the fruiting rates of hybrid seeds obtained from cross combinations with different affinity levels differ, there is no direct relationship between the degree of affinity and the level of fruiting rate. The fruiting rates of hybrid seeds obtained from different cross combinations were all above 70%, reaching a maximum of 85%, significantly exceeding the 40% fruiting rate of Fengdan obtained by self-pollination. Therefore, artificial pollination can improve the fruiting rate of Fengdan. This result is consistent with literature reports. Regarding the single seed weight, no significant differences were observed between different cross combinations, however, the single seed weight of seeds obtained from the HFR×FD cross combination was slightly higher at 0.4647g. The single seed weight of seeds obtained from other cross combinations, such as DFG, YLC, and the cross of YPH with FD, was approximately 0.44g, indicating that the size of the seeds obtained from the hybrids of the selected Jiangnan Peony varieties and Fengdan is relatively uniform.

[0054] The germination rates of hybrid seeds obtained from different cross combinations are not uniform, and this is related not only to the affinity between the father and mother plants but also to the timing of seed harvesting. According to the results of this invention, the germination rate of seeds obtained from the cross of "Yulou Chun," "Yipin Hong," and Feng Dan was 78% or higher, and the germination rate of seeds obtained from the cross of "Da Fu Gui," "Beni Fu Yong," and Feng Dan was also 59% or higher. According to the literature, seeds obtained from self-pollination of Feng Dan have a germination rate of 50% or less if no special treatment is applied. Therefore, it can be seen that the seeds from all the cross combinations obtained in this invention have a significantly higher germination rate than seeds obtained from self-pollination of Feng Dan.

[0055] Various methods can be considered to create water-resistant seed traits. Among them, one relatively traditional and effective method is to improve the water resistance of offspring by crossing a highly water-resistant father with a highly water-resistant mother. Ornamental peony varieties from the Jiangnan region of China, such as "Yulou Chun," "Yipin Hong," and "Hong Fuyong," are highly water-resistant and very well adapted to the rainy climate of Jiangnan, making them ideal fathers. Feng Dan is the main variety of oil peony cultivated in the Jiangnan region of China, and with its strong adaptability and excellent fruiting ability, it is one of the best choices as a mother for crosses. By crossing a highly water-resistant father with a mother with excellent adaptability and fruiting ability, it is expected that water-resistant offspring traits can be created. In this invention, we crossed ornamental peony varieties from Jiangnan with Feng Dan and analyzed the water resistance of the resulting hybrid offspring. The water resistance of the hybrid offspring seedlings was evaluated from three aspects: phenotypic, morphological, and physiological.

[0056] From a phenotypic perspective, hybrid progeny obtained by crossing 'Yulou Chun', 'Yipin Hong', and 'Feng Dan' exhibit increased leaf thickness and significantly higher water resistance than the parent 'Feng Dan'. This indicates that the cross alters the leaf characteristics of the plants, resulting in improved resistance to flood stress. Morphological indicators show that while the relative chlorophyll content of leaves decreases when 'Feng Dan' plants are subjected to flood stress, it was confirmed that the relative chlorophyll content did not decrease in hybrid progeny seedlings, but rather increased. This is consistent with the phenotypic results. When plants are subjected to flood stress, the root system in the underground part stops growing or slows down due to oxygen deficiency, and consequently, the above-ground part also stops growing due to insufficient nutrient supply. From the results of this invention, it was found that both uncrossed 'Feng Dan' and hybrid progeny stopped growing above ground and suppressed underground growth after flood treatment, and the root cap ratio also decreased compared to untreated plants, but the decrease in hybrid progeny was significantly smaller than that of the control. This indicates that the peony plants obtained through crossbreeding have improved their ability to adapt to flood stress.

[0057] Under flood stress, plants experience metabolic disruption due to oxygen deficiency in the root system, leading to excessive carbohydrate consumption in the above-ground parts. To adapt to flood stress and mitigate damage, metabolic enzymes such as sucrose synthase (SS), α-amylase (RAMY), alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC) are activated, resulting in self-regulation. In this invention, the activity of four enzymes and soluble protein content were analyzed in hybrid progeny obtained from different cross combinations.

[0058] As a result, overall, compared to the uncrossed control *Platanthera japonica* FD, the water tolerance physiological indicators SS, RAMY, ADH, and PDC of the hybrid progeny obtained from the cross combination YLC×FD were all significantly higher than those of the control FD. The water tolerance physiological indicators SS, RAMY, PDC, and PRO of the hybrid progeny obtained from the cross combination YPH×FD were also higher than those of the control FD, and in particular, the three indicators SS, PDC, and PRO reached significant levels. During the flood treatment period, ADH and PDC reached their peak values ​​on the 7th day, while SS, RAMY, and PRO reached their peak values ​​on the 5th day. These results indicate that the progeny traits obtained by crossing promoted the activity of enzymes related to sugar metabolism and reduced the degree of flood stress experienced by the plants. Furthermore, the results of this invention demonstrate that new water-tolerant traits can be created by crossing water-tolerant traits with water-tolerant traits through crossbreeding.

Claims

1. A method for improving the water resistance of oil-producing peonies and increasing their production, Using the oil-producing peony variety FD as the mother plant, we selected and crossed sire plants DFG, YLC, YPH, and HFR that have different affinity characteristics, resulting in DFG×FD, YLC×FD, YPH×FD, HFR×FD, A method characterized by including obtaining the above four hybrid combinations.

2. The method according to claim 1, characterized in that the aforementioned hybrid combination is YLC × FD.

3. The method according to claim 2, characterized in that coronatin is used as a substitute for water-soaked seeds during seed germination.

4. The method according to claim 3, characterized in that the concentration of coronatin is 0.1 μmol / L to 0.5 μmol / L.

5. The method according to claim 4, characterized in that the concentration of coronatin is 0.5 μmol / L.

6. The use of coronatin to improve the water resistance of oil-grown peonies, characterized by a coronatin concentration of 0.1 μmol / L to 0.5 μmol / L.

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