Method for improving waterlogging tolerance and increasing yield of oil peonies

Abstract

The invention provides a method for improving waterlogging tolerance and increasing yield of oil peonies, which comprises the following steps: selecting different genetic male parents DFG, YLC, YPH and HFR to hybridize by taking an oil peony variety FD as a female parent to obtain a hybridized combination: (1) DFG * FD with relatively close genetic relationship; (2) YLC * FD for a medium genetic relationship; (3) YPH * FD for the farther genetic relationship; and (4) HFR * FD with relatively far genetic relationship. In addition, the method further comprises the step that coronatine is used for replacing hydrophilic seed soaking when the seeds germinate. By means of the method, the waterlogging tolerance of the oil peonies is obviously improved, and the yield is increased.

Description

Technical Field

[0001] The invention relates to a method for improving waterlogging resistance and yield of oil-bearing peony, and particularly relates to a method for improving waterlogging resistance of oil-bearing peony by hybridization and seed soaking with coronatine, and simultaneously improving yield of oil-bearing peony. Background Art

[0002] 'Fengdan' is the main variety of oil-bearing peony in the Jiangnan region. It is a new type of woody oil-bearing tree species with the characteristics of drought resistance, barrenness resistance, severe cold resistance, and shade resistance. Its root system is fleshy and sensitive to water, and it is a type of plant that is not tolerant to waterlogging. Due to the heavy rainfall in the south, waterlogging often occurs, which greatly affects the yield of 'Fengdan'. Every year, the yield of 'Fengdan' is reduced by more than 40% due to rain. Especially in the Jiangnan region, the pod-bearing period of 'Fengdan' happens to meet the plum rain season. The root system is prone to disease and even rot due to long-term waterlogging. The leaves of the aboveground part begin to turn yellow and black, and the fruit pods begin to mold before they are mature. Therefore, in order to fundamentally solve the problem, it is urgent to select some waterlogging-resistant oil-bearing peony varieties to solve the problem of reduced production of oil-bearing peonies due to waterlogging intolerance. Cultivating new Fengdan varieties with good waterlogging resistance through hybrid breeding and applying them to production is of great significance to promoting the development of the peony industry.

[0003] Hybrid breeding is a traditional breeding method. Traditional breeding methods are still the main way to breed new varieties because of their simple operation and effectiveness. So far, many researchers have obtained new peony germplasm by hybridizing oil-bearing peonies with ornamental peonies. The main breeding goals are to improve ornamental quality, enhance stress resistance and cultivate special varieties (such as cut flowers, potted plants and oil). Among them, the breeding direction for enhancing stress resistance mainly includes heat resistance, cold resistance, drought resistance, salt and alkali resistance, heavy metal resistance and pest and disease resistance, while there are almost no reports on breeding with waterlogging resistance as the breeding goal, which is limited to the evaluation of waterlogging resistance between different peony varieties. Through hybrid breeding, hybridizing varieties with strong waterlogging resistance and varieties with weak waterlogging resistance, thereby improving the waterlogging resistance of varieties that are not waterlogged resistant, is the most effective and reliable method. However, there has been no report on the creation and invention of waterlogging-resistant germplasm of 'Fengdan' at home and abroad, and waterlogging-resistant oil-bearing peony varieties are also urgently needed in production.

[0004] In the present invention, different varieties of Jiangnan ornamental peonies are interspecifically hybridized with 'Fengdan', the fruiting rates of different hybrid combinations and the germination rates of hybrid seeds are invented, and flooding tests are conducted on the seedlings of the hybrid offspring and their parents, and the morphological and physiological indicators of the seedlings are measured to screen out the waterlogging-resistant hybrid offspring. As a result of the invention, a new waterlogging-resistant 'Fengdan' germplasm is obtained, which provides variety resources for the southern region with more rain, especially the Jiangnan region, thereby fundamentally solving the bottleneck problem faced by the production of 'Fengdan' and providing favorable resource guarantees for the industrial development of oil-bearing peonies.

[0005] Coronatine (COR) is a compound isolated from Pseudomonas syringae. It has a similar chemical structure to jasmonic acid compounds (JAs) and many similar physiological functions. The invention shows that COR has many physiological functions, such as regulating plant growth and development, inducing related secondary metabolites, and enhancing plant resistance to environmental stress (Xu Ruqiang, 1998; Ai Lin, 2008). Qi Fuguo et al. (2006) believed that under low temperature conditions, COR treatment can increase the content of soluble protein in wheat leaves, reduce relative conductivity and MDA content; Ai Lin et al. (2008) reported that under drought conditions, COR treatment can maintain a higher relative water content of rice leaves, promote the accumulation of soluble protein in seedling leaves, reduce plasma membrane permeability, and maintain the integrity of the cell plasma membrane.

[0006] Patent document CN201810769231 discloses a breeding method for improving the drought resistance of oil-bearing peony. The method selects an oil-bearing peony variety with excellent traits as the female parent, selects an oil-bearing peony variety with stable yield as the male parent, hybridizes and harvests the hybrid first-generation seed F1, plants F1 and mixes and harvests to obtain hybrid second-generation seed F2, backcrosses the F2 plant with the female parent to obtain the backcross first-generation seed BC1, and the BC1 plant is backcrossed with the female parent to obtain the backcross second-generation seed BC2, and finally plants the backcross second-generation seed BC2, self-pollinates for 3 to 4 generations, and selects the best strain as a new variety of oil-bearing peony; during the period, a stress agent is used for water stress treatment, which can strangle the germination of drought-intolerant seeds in the cradle, reduce the production of false positive drought-resistant seeds, reduce the total sample size of subsequent hybridization steps, reduce workload, and improve breeding efficiency.

[0007] Patent document CN202010947381 discloses a method for improving the drought resistance of oil-bearing peonies using methyl jasmonate. Specifically, methyl jasmonate is sprayed on the leaves of oil-bearing peonies under cultivation. This method significantly improves the net photosynthetic rate of the oil-bearing peony leaves, reduces the damage caused by drought stress to the peony, and improves the peony's ability to resist drought stress.

[0008] The above-mentioned prior art still does not solve the problem of waterlogging resistance of oil-bearing peony. Summary of the invention

[0009] Technical Problems to be Solved by the Invention

[0010] In view of the above problems, the technical problem to be solved by the present invention is to cultivate a new oil-bearing peony variety with waterlogging resistance, and a method for improving the waterlogging resistance of the new oil-bearing peony variety and increasing its yield.

[0011] Means for Solving the Problems of the Invention

[0012] The present invention provides a method for improving the waterlogging resistance and increasing the yield of oil peony, comprising the following steps:

[0013] The oil-bearing peony variety FD was used as the female parent and different related male parents DFG, YLC, YPH, and HFR were selected for hybridization to obtain the following hybrid combinations: (1) closely related: DFG×FD; (2) moderately related: YLC×FD; (3) distantly related: YPH×FD; (4) distantly related: HFR×FD.

[0014] The method of the present invention further comprises: using coronatine to replace hydrophilic seed soaking during seed germination.

[0015] The concentration of the above coronatine is 0.1 μmol / L to 0.5 μmol / L.

[0016] The present invention also provides the use of coronatine in improving the waterlogging resistance of oil-bearing peony, wherein the concentration of the coronatine is 0.1 μmol / L to 0.5 μmol / L.

[0017] Technical Effects

[0018] The new oil-bearing peony variety obtained according to the method of the present invention not only exhibits waterlogging resistance in the rainy season, but also ensures a higher yield when setting seeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Phenotypic changes of tree peony after waterlogging treatment (from left to right: FD Fengdan seedlings, YPH×FD hybrid offspring, YLC×FD hybrid offspring).

[0021] Figure 2 Physiological indicators of peony hybrid offspring under waterlogging stress. Determination results of plant sucrose synthase (SS). Different lowercase letters on the short bars indicate statistically significant differences between different plants at the P < 0.05 level within the same treatment period; n = 3, the same below.

[0022] Figure 3 The results of the determination of plant α-amylase, a physiological indicator of peony hybrid offspring under waterlogging stress.

[0023] Figure 4 The results of the determination of plant alcohol dehydrogenase (ADH), a physiological indicator of peony hybrid offspring under waterlogging stress.

[0024] Figure 5 The results of the determination of plant pyruvate decarboxylase (PDC), a physiological indicator of peony hybrid offspring under waterlogging stress.

[0025] Figure 6 The results of determination of plant soluble protein (s-protein), a physiological indicator of peony hybrid offspring under waterlogging stress. DETAILED DESCRIPTION

[0026] The present invention will be further explained below in conjunction with specific embodiments.

[0027] Coronatine (COR) is a compound isolated from the culture medium of Pseudomonas syingae pv. Atropurpurea in 1977. It can cause diffuse Verticillium wilt in many plants.

[0028] COR is a structural and functional analog of jasmonic acid, and its molecular formula is C 18 H 25 NO4, with a molecular weight of 319.4 Da, is composed of a coronamic acid (CMA) containing an α-amino acid and a coronafacic acid (CFA) with a polyketide structure linked by an amide bond, as shown in Chemical Formula 1. It has the same alkane structure as methyl jasmonate (hereinafter referred to as JA-Me), and the activity of COR is much higher than that of jasmonic acid. COR can stimulate the secondary metabolism of plants, produce a variety of plant toxins, and participate in stress regulation. Its mode of action is similar to that of jasmonic acid. There are inventions showing that both JA and COR can improve the drought resistance of sorghum seedlings, and COR is better than JA. The regulation of COR shows a certain dose-effect relationship, that is, it promotes plant growth at low concentrations and inhibits plant growth at high concentrations.

[0029] Coronatine has the following structural formula:

[0030] Chemical formula 1

[0031]

[0032] The coronatine of the present invention can be obtained by industrial fermentation production (such as ZL200510011466.2; ZL200510085280.1; L200710099033.6; ZL200810119153.2). It can also be purchased directly from a chemical company, such as Sigma's product number C8115, and stored in a -20°C refrigerator. Before use, it is prepared into a 1 mmol / L solution with double distilled water, and diluted with tap water or field water when used.

[0033] The concentration of coronatine is 0.05 to 1 μmol / L, more preferably 0.1 to 0.5 μmol / L.

[0034] Example

[0035] 1 Materials and methods

[0036] 1.1 Test materials

[0037] The test material 'Fengdan' (hereinafter referred to as FD) was introduced from Tongling, Anhui, and is a 10-year-old seedling; the Jiangnan ornamental peony 'Poinsettia' (hereinafter referred to as YPH), 'Yulouchun' (hereinafter referred to as YLC), 'Hong Furong' (hereinafter referred to as HFR) and 'Dafugui' (hereinafter referred to as DFG) are local varieties grown in Zhejiang, with pink and red color, and chrysanthemum type, crown type, and pavilion type.

[0038] 1.2 Hybrid combination

[0039] Different hybrid combinations were selected according to the relationship between different Jiangnan peony varieties. The main hybrid combinations are: (1) closely related: DFG×FD; (2) medium related: YLC×FD; (3) distantly related: YPH×FD, HFR×FD.

[0040] 1.3 Methods

[0041] Choose a sunny day between 9:00-11:00 in the morning. At the end of March, select the female parent whose buds have been broken and exposed for 1-2 days, whose petals are slightly open and in the initial stage of opening, and emasculate and bag them; in early April, when the male parent's stamens mature and gradually begin to shed pollen, and the petals are fully open in the full flowering period, use tweezers to remove the pollen into a test tube filled with desiccant, dip a small amount of pollen with a cotton swab, and apply it to the stigma of the emasculated female parent, and artificially pollinate it. After pollination, continue to bag it and fix it with a paper clip at the bottom to prevent insect pollination. On the 7th day after artificial pollination, you can remove the bag and let it receive natural light. From July 30th to August 5th, when the fruit pods turn from green to crab yellow, they can be harvested. The harvested pods were placed in a dark and ventilated place indoors to dry for about a week until the pods were completely cracked. The seeds were peeled off manually and the number of seeds, seed weight, and fruit setting rate (number of pods / number of pollinations*100) were counted. The peeled seeds were soaked in clean water for 24 hours and then sown. The number of seedlings of each combination was counted and the germination rate (number of seedlings / number of sowings*100) was calculated.

[0042] In addition, in order to test whether soaking seeds with different concentrations of methyl jasmonate and coronatine can stimulate waterlogging resistance, different concentrations of methyl jasmonate or coronatine were used instead of water for soaking seeds. The concentrations of methyl jasmonate or coronatine were 0.1μmol / L, 0.5μmol / L, and 1.0μmol / L. The test object was YLC×FD.

[0043] 1.4 Analysis of waterlogging resistance

[0044] The seeds of hybrid offspring with full grains and their parents were selected and sown in 90mm double-color pots. When the seedlings grew two leaves, they could be transplanted, one plant per pot. After 2 months of open-air cultivation, seedlings with consistent growth were selected for flooding test. The potted seedlings were placed in a water tank and watered until the pot soil was submerged by 2cm. The plants were observed for 1 week, and their morphological indicators such as plant height, root length, and root-crown ratio were investigated. The relative content of chlorophyll was determined, and the top leaves were collected as test materials to prepare for the determination of physiological indicators related to waterlogging stress, such as sucrose synthase (SS), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), α-amylase (RAMY) activity and soluble protein (PRO) content. Finally, various data were counted, and the waterlogging resistance of hybrid offspring and parents was comprehensively evaluated, and hybrid offspring with strong waterlogging resistance were selected.

[0045] 1.5 Measurement methods of the above enzymes and proteins

[0046] Sucrose synthase (SS): The activity of sucrose synthase was determined using the plant sucrose synthase ELISA kit from Jianglai Biotechnology Co., Ltd.

[0047] Pyruvate decarboxylase (PDC): The activity of Pyruvate Decarboxylase was determined using the Plant Pyruvate Decarboxylase ELISA kit from Jianglai Biotechnology Co., Ltd.

[0048] Alcohol dehydrogenase (ADH): The activity of ADH was determined using the plant alcohol dehydrogenase ELISA kit from Jianglai Biotechnology Co., Ltd.

[0049] α-Amylase (RAMY): The plant α-amylase ELISA detection kit of Jianglai Biotechnology Co., Ltd. was used for determination.

[0050] Soluble protein (sprotein): The plant soluble protein ELISA detection kit of Jianglai Biotechnology Co., Ltd. was used for determination.

[0051] 1.6 Detection method of relative chlorophyll content

[0052] The chlorophyll was measured using a JC-YLC chlorophyll meter.

[0053] 2 Results and analysis

[0054] 2.1 Fruiting situation of different hybrid combinations

[0055] In order to obtain the fruit setting of different hybrid combinations, the number of pods and seeds collected from each combination was investigated, and the hybrid fruit setting rate of each combination was calculated based on the number of pollinations. The fruit setting rates of the four hybrid combinations were all above 70%, among which the combination YLC×FD had the highest fruit setting rate, reaching 85%, followed by the combination HFR×FD, the combination YPH×FD and the combination DFG×FD, with fruit setting rates of 75%, 71.66% and 70%, respectively. The seeds obtained from each combination were weighed, and the single seed weight of the seeds was calculated based on the number of seeds. As can be seen from Table 1, the single seed weights of the hybrid seeds obtained from the four hybrid combinations were relatively close, ranging from 443.3 to 464.7 mg, with little difference.

[0056] Table 1 Fruiting situation of different hybrid combinations

[0057]

[0058] 2.2 Seed germination of different hybrid combinations

[0059] In order to further clarify the seed germination of different hybrid combinations, we selected 150 seeds with full grains and uniform size from the hybrid seeds obtained from each hybrid combination, and counted their germination after sowing. As can be seen from Table 2, the germination of seeds in different hybrid combinations is significantly different. Among them, the combination with the highest germination rate is YLC×FD, followed by the combination of YPH×FD. The combinations with lower germination rates are DFG×FD and HFR×FD, with germination rates of 80.00%, 78.67%, 60.00% and 59.33% respectively. Overall, the germination rates of the four hybrid combinations are relatively high, all above 59%.

[0060] Seed soaking with different concentrations of methyl jasmonate and coronatine had a small effect on the germination rate of YLC×FD, specifically, 1.0 μmol / L methyl jasmonate and coronatine reduced the germination rate.

[0061] Table 2 Seed germination rate of different hybrid combinations

[0062]

[0063] Table 3 Germination rate of YLC×FD seeds after soaking in different solutions

[0064]

[0065] 2.3 Waterlogging tolerance of hybrid offspring

[0066] According to the experimental results of 2.2, we selected two hybrid combinations YPH×FD and YLC×FD with higher germination rates, and 6 seed soaking groups with different concentrations of methyl jasmonate and coronatine (as shown in Table 3) to further explore the waterlogging resistance of the hybrid offspring. The unhybridized 'Fengdan' mother plant was used as a control, and observations were made from the phenotypic, morphological and physiological levels for 1 week, resulting in the following results.

[0067] 2.3.1 Phenotypic traits

[0068] From the appearance, the leaves of the seedlings of the control 'Fengdan' were thinner and lighter in color; the leaves of the hybrid seedlings obtained from the hybrid combinations YPH×FD and YLC×FD were thicker and darker in color. The phenotypic changes were observed one week after the waterlogging treatment. Figure 1 It was found that the leaves of the control group began to wilt slightly and droop, while the hybrid seedlings obtained through hybridization performed normally, with flat leaves and no wilting symptoms.

[0069] There was no difference in the hybrid seedlings of the hybrid combination YLC×FD (shown in Table 3) of the six groups soaked with different concentrations of methyl jasmonate and coronatine. The leaves of the six groups of seedlings were flat and no wilting symptoms appeared (not shown).

[0070] 2.3.2 Results of morphological index determination

[0071] Hybrid seedlings and control seedlings were treated with waterlogging, and their morphological indicators were investigated. From the waterlogging treatment group and the control group without waterlogging treatment, the plant height of the waterlogging treatment group did not change, while the plant height of the control group without waterlogging treatment increased slowly, about 0.2-0.3cm; after waterlogging treatment, the relative chlorophyll content of leaves FD decreased by 8.1%, YPH×FD and YLC×FD increased by 12.5% ​​and 0.38%, respectively; the root length and root-to-crown ratio of the waterlogging treatment group were significantly lower than those of the control group, and the root length of YPH×FD and YLC×FD decreased by 27.08% and 24.42%, respectively, and the root-to-crown ratio decreased by 13.33% and 21.08%, respectively. From the two groups of hybrid seedlings and control seedlings, the plant height, root length and root-to-crown ratio were roughly affected by waterlogging. All were inhibited by waterlogging, the plants stopped growing, and the root length and root-to-crown ratio also showed a downward trend; the relative content of chlorophyll was just the opposite, the hybrid seedlings did not decrease but increased, while the control seedlings showed a downward trend; from the perspective of the decrease in the root-to-crown ratio, the decrease in the hybrid seedlings (13-21%) was lower than that in the control seedlings (31.88%).

[0072] The hybrid seedlings of the hybrid combination YLC×FD (shown in Table 3) of the 6 groups of seed soaking with different concentrations of methyl jasmonate and coronatine showed a significant increase in the relative chlorophyll content in the 0.5 μmol / L COR treatment group compared with the hybrid seedlings of YLC×FD soaked in water, and the root-to-shoot ratio of this group also decreased significantly, as shown in Table 5.

[0073] Table 4 Determination of morphological indexes of peony hybrid offspring treated with waterlogging

[0074]

[0075] Table 5 Determination of morphological indexes of waterlogging in different seed soaking groups of peony after hybridization YLC×FD

[0076]

[0077] 2.3.3 Results of physiological indexes

[0078] Using FD as the control, the waterlogging resistance of the hybrid offspring obtained from different hybrid combinations was determined by measuring the physiological indicators related to waterlogging, such as SS, PDC, ADH, RAMY, ADH and PRO. Figure 2 From the above data, it can be seen that the sucrose synthase (SS) activities of FD, YPH×FD, and YLC×FD were almost the same before waterlogging treatment. With the extension of waterlogging treatment time (0-7d), the SS activities of the three showed a trend of first increasing and then decreasing, and all reached the highest level on the 5th day of waterlogging treatment. In the first 3 days of waterlogging treatment, the SS activity of the hybrid combination YLC×FD was significantly higher than that of the control FD; by the 5th day, the SS activity of the three was not significantly different; until the 7th day, the sucrose synthase activities of the hybrid combinations YPH×FD and YLC×FD were significantly higher than those of the control FD.

[0079] from Figure 3 From the above data, it can be seen that before waterlogging treatment, the α-amylase (RAMY) activities of the hybrid combinations YPH×FD and YLC×FD were significantly higher than those of the control FD. With the extension of waterlogging treatment time (0-7d), the RAMY activities of the three showed a trend of first increasing and then decreasing. Among them, the hybrid combination YLC×FD reached the highest level on the 3rd day of waterlogging treatment, and the hybrid combination YPH×FD and the control FD reached the highest level on the 5th day of waterlogging treatment. The RAMY activity of the control FD increased rapidly one day after waterlogging treatment, and the change range was significantly higher than that of the hybrid combinations YPH×FD and YLC×FD. During the waterlogging treatment, the RAMY activity of the hybrid combination YPH×FD was not significantly different from that of the control FD. The RAMY activity of the hybrid combination YLC×FD was significantly higher than that of the control FD on the 0th, 3rd and 7th days of waterlogging treatment.

[0080] from Figure 4From the perspective of the results, when not treated with waterlogging, the alcohol dehydrogenase (ADH) activities of the hybrid combinations YPH×FD and YLC×FD were significantly lower than those of the control FD, among which the ADH activity of the hybrid combination YLC×FD was the lowest. With the extension of the waterlogging treatment time (0-7d), the ADH activity of the control FD showed a trend of first increasing and then decreasing, reaching the highest level on the 5th day; the ADH activity of the hybrid combination YPH×FD showed a continuous upward trend until the 7th day, when its ADH activity was significantly higher than that of the hybrid combination YPH×FD and the control FD. From the perspective of all treatment times, the ADH activity of the hybrid combination YPH×FD was significantly lower than that of the control FD.

[0081] from Figure 5 From the results of the experiment, the pyruvate dehydrogenase (PDC) of the hybrid combinations YPH×FD and YLC×FD were significantly lower than that of the control FD before waterlogging treatment. With the extension of waterlogging treatment time (0-7d), the PDC activity of the control FD showed a trend of first increasing and then decreasing, reaching the highest level on the 5th day of waterlogging treatment; the PDC activity of the hybrid combinations YPH×FD and YLC×FD showed a trend of first increasing rapidly and then increasing slowly, reaching the highest level on the 7th day. During the waterlogging treatment, the PDC activity levels of the hybrid combinations YPH×FD and YLC×FD were significantly higher than that of the control FD, while there was no significant difference between the two hybrid combinations.

[0082] from Figure 6 From the results of the experiment, it can be seen that before waterlogging treatment, the soluble protein (PRO) content of the hybrid combinations YPH×FD and YLC×FD was significantly higher than that of the control FD. With the extension of waterlogging treatment time (0-7d), the PRO content of the three showed a trend of first increasing and then decreasing, and reached the highest level on the 5th day of waterlogging treatment. After 1d of waterlogging treatment, the PRO content of the hybrid combination YPH×FD and the control FD increased rapidly and was higher than that of the hybrid combination YLC×FD. The PRO content of the hybrid combination YLC×FD increased rapidly during the 1-3d of waterlogging treatment, reaching a level almost the same as that of the hybrid combination YPH×FD, and significantly exceeding that of the control FD. On the 5th and 7th days of waterlogging treatment, the PRO content of the hybrid combination YPH×FD was significantly higher than that of the hybrid combination YLC×FD.

[0083] 2.4 Seed yield of hybrid offspring

[0084] The nursery of 11 groups obtained by ramet seedling raising shown in Table 5 was transplanted to the experimental field of Zhejiang Provincial Garden Plant and Flower Invention Institute in March of the third year, with a plant spacing of 60 cm and a row spacing of 100 cm. Other fertilization, intertillage and weeding were carried out according to conventional field management and pest control methods. The fruit pods were harvested when they turned from green to yellow and cracked in October of the same year. After harvesting, they were threshed and dried in time to keep the moisture content of the seeds at 10%-12%. The harvested seeds were weighed and converted into per mu yield, and the results are shown in Table 7.

[0085] Table 7 Seed yield of oil-producing peony

[0086]

[0087] Peony varieties of different provenances, whether it is the hybridization of Central Plains peony and Fengdan, or the hybridization of Japanese peony and Fengdan, or the hybridization of Jiangnan peony and Fengdan, all do not have the phenomenon of hybridization incompatibility, but the hybrid offspring characteristics obtained by hybridization between different varieties are obviously different. The results of the present invention show that the hybrid combinations of different affinities have different hybrid seed setting rates, but the distance of affinities has no direct connection with the height of the setting rate. Through different hybrid combinations, the hybrid seed setting rate obtained is all above 70%, the highest reaching 85%, which is much higher than the setting rate of 40% of Fengdan self-pollination, indicating that the setting rate of Fengdan can be improved by artificial assisted pollination, which is consistent with the results reported in the literature. There was no obvious difference in the single-grain weight of seeds among different hybrid combinations. Except for the hybrid combination HFR×FD, which had a slightly higher single-grain weight of 0.4647g, the single-grain weight of hybrid seeds obtained by hybridizing other hybrid combinations DFG, YLC and YPH with FD was around 0.44g, indicating that the hybrid seeds obtained by hybridizing several Jiangnan peony varieties selected in this experiment with Fengdan had relatively uniform grain size.

[0088] The germination rate of hybrid seeds obtained from different hybrid combinations varies, which is not only related to the affinity between the male and female parents, but also to the harvest period of the seeds. From the results of the present invention, the germination rate of the seeds obtained by hybridizing 'Yulouchun' and 'Pinsettia' with Fengdan is higher than 78%; the germination rate of the seeds obtained by hybridizing 'Da Fugui' and 'Hong Furong' with Fengdan is also above 59%. According to literature reports, the natural germination rate of hybrid seeds obtained by self-pollination of Fengdan is less than 50% without any treatment. It can be seen that the germination rate of seeds obtained from all hybrid combinations of the present invention is significantly higher than that of seeds obtained by self-pollination of Fengdan.

[0089] Creating waterlogging-resistant germplasm can be achieved through a variety of ways, among which hybridizing male and female parents with good waterlogging resistance to improve the waterlogging resistance of offspring is one of the more traditional and effective methods. Local ornamental peony varieties in Jiangnan, such as 'Yulouchun', 'Poinsettia' and 'Hong Furong', have strong waterlogging resistance and can adapt well to the Jiangnan climate with more rain, and are more ideal male parents. Fengdan is the main variety of oil peony in the Jiangnan region. It not only has strong adaptability, but also has very good fruiting ability, and is one of the best choices as a hybrid female parent. Hybridizing a male parent with strong waterlogging resistance with a female parent with good adaptability and fruiting ability is expected to create offspring germplasm with good waterlogging resistance. The present invention hybridizes Jiangnan ornamental peony varieties with Fengdan, and analyzes the waterlogging resistance of the obtained hybrid offspring. The waterlogging resistance of the hybrid offspring was evaluated from three aspects: phenotype, morphology and physiology. From the phenotypic characteristics, the offspring of 'Yulouchun' and 'Pinghong' hybridized with Fengdan not only have increased leaf thickness, but also have significantly higher waterlogging resistance than the parent 'Fengdan', indicating that the characteristics of the plant leaves have been changed by hybridization, thereby changing the ability of the plant to endure waterlogging stress. From the morphological index, when the Fengdan plant is subjected to waterlogging stress, the relative chlorophyll content of its leaves will decrease accordingly, but the relative chlorophyll content of the seedlings obtained by hybridization does not decrease or even increases, which is also consistent with the results of phenotypic characteristics. After the plant is subjected to waterlogging stress, the root system of its underground part will stop growing or grow slowly due to lack of oxygen, thereby causing the aboveground part to stop growing due to insufficient nutrient delivery. From the results of the present invention, it can be seen that whether it is the unhybridized Fengdan or the offspring obtained by hybridization, after waterlogging treatment, its aboveground part stops growing, the underground part growth is inhibited, and the root-crown ratio is reduced compared with the untreated plant, but the decline of the hybrid offspring is obviously smaller than that of the control. It shows that the ability of the peony plant obtained by hybridization to adapt to waterlogging stress has been improved.

[0090] Under waterlogging stress, plants suffer from a lack of oxygen in their roots, which causes a large amount of carbohydrates in the aboveground parts to be consumed, leading to metabolic disorders. In order to adapt to flooding stress and reduce damage to the plants themselves, some enzymes related to metabolism, such as SS, RAMY, ADH and PDC, will be activated to perform self-regulation. Therefore, the present invention analyzed the above four enzyme activities and soluble protein content of the hybrid offspring obtained from different hybrid combinations.

[0091] The results showed that, overall, compared with the unhybridized control Fengdan FD, the hybrid offspring obtained by the hybrid combination YLC×FD had significantly higher waterlogging resistance physiological indicators such as SS, RAMY, ADH and PDC than the control FD; the hybrid offspring obtained by the combination YPH×FD had higher waterlogging resistance physiological indicators such as SS, RAMY, PDC and PRO than the control FD, among which SS, PDC and PRO all reached significant levels. During the waterlogging treatment, except for ADH and PDC, which reached the highest level on the 7th day, the other three indicators such as SS, RAMY and PRO all reached the highest level on the 5th day. This shows that the offspring germplasm obtained by hybridization promotes the function of enzymes related to sugar metabolism in the hybrid offspring, reducing the degree of waterlogging stress suffered by the plants. The results of this invention further confirm that new waterlogging-resistant germplasm can be obtained by hybrid breeding by hybridizing waterlogging-resistant germplasm with waterlogging-intolerant germplasm.

Claims

1. A method for improving the waterlogging resistance and increasing the yield of oil-bearing peony, characterized in that: The following steps are involved: Taking the oil peony variety FD as the female parent, different related male parents DFG, YLC, YPH, and HFR were selected for hybridization to obtain the hybrid combination: (1) Closely related: DFG×FD; (2) Moderately related: YLC×FD; (3) Distantly related: YPH×FD; (4) Very distantly related: HFR×FD.

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

3. The method according to claim 2, characterized in that The following steps are also included: When seeds are germinating, use coronatine instead of hydrophilic seed soaking.

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

5. The method according to claim 4, characterized in that The concentration of coronatine was 0.5 μmol / L.

6. Application of coronatine in improving waterlogging resistance of oil-bearing peony, characterized in that: The concentration of the coronatine is 0.1 μmol / L to 0.5 μmol / L.

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