A review of 'Fengdan' peony cultivation and industrial development
_Li Zijian
Funds: Shanghai Science and Technology Program (21DZ1202000), Shanghai Central Government Guidance Local Science and Technology Development Fund (YDZX20223100001003), Shanghai Municipal Greening and City Appearance Administration (G222412), National Natural Science Foundation of China (32270399).
Peony (Paeonia suffruticosa Andr.) is a deciduous shrub of the peony group of the peony family Paeoniaceae, which is the traditional famous flower of the mainland, the national color is fragrant, symbolizes wealth and auspiciousness, is widely loved by the world, and is known as the "king of flowers". 'Fengdan' is currently the largest type of peony planted and cultivated in China, the root is used as a traditional Chinese medicine "Danpi" into medicine, stems, leaves, flowers can also extract paeonol and peony glycosides. As a new resource plant, the seeds of 'Fengdan' are rich in essential polyunsaturated fatty acids such as linoleic acid (C18:2) and α-linolenic acid (C18:3), which can be used as high-quality edible oil and dietary supplement. The ornamental nature of 'Fengdan' is different from the traditional peony's flowers, which are large and colorful, graceful and luxurious, and its flowers are single-petaled, mostly white, with the texture of oil paintings, noble and pure. As a plant integrating medicinal oil, 'Fengdan' has broad market prospects, and has also caused a great research boom. The publication of the genome map of 'Fengdan' has brought the scientific research of peony into the genomic era, opened a new chapter in molecular breeding, functional analysis of special excellent traits and industrial utilization of peony, and brought the basic research of peony to a new height. The product market at the end of the peony industry chain has entered a blowout development, but as an intermediate link, the peony precision cultivation and maintenance management technology is lagging behind, and there is no unified replicable and enforceable standard, especially in the research on the fine cultivation of 'Fengdan', the high-yield cultivation of medicinal and oil-used 'Fengdan' and the factors affecting the high yield of seeds. In this paper, we will mainly focus on the environmental factors affecting the growth and development of 'Fengdan', the effects of various nutrient elements on the yield of 'Fengdan' danpi and grains, and the research and progress of 'Fengdan' fine cultivation and maintenance technology, in order to provide a reference for the sustainable and in-depth development of the entire 'Fengdan' industry and promote the upgrading of the peony industry.
1. The development of 'Fengdan' medicinal oil concept
1.1 Inheritance and innovation of medicinal value
Peony root bark is dried and dried, that is, the Danpi in the traditional medicinal materials of the mainland, which has the effects of clearing heat and analgesia, invigorating blood and removing stasis, etc., and after the study of modern pharmacology, it is found that the function of Danpi is not only that, the research shows that Danpi also has the effect of regulating the cardiovascular system and immune system, protecting the liver and kidneys, dissolving inflammation, sterilization and disinfection. In the context of the post-epidemic era, people pay more attention to the treatment and health care of traditional Chinese medicine, and various traditional Chinese medicinal materials have also been revitalized. The main pharmacological components in peony are paeonol and paeoniflorin, especially paeoniflorin plays an important role in the treatment of postoperative recovery after stroke. The research on medicinal active ingredients such as peony glycosides is not only limited to pharmacological and clinical aspects, but also the basic raw materials for the preparation of a variety of drugs as natural and unique medicinal active products of Paeoniaceae plants, so the biosynthesis pathways of pharmacological components such as peony glycosides are also the focus of research.
In the main peony production area of the mainland, the cultivation and production of medicinal peony occupies a considerable proportion, the cultivation area is vast, and the varieties are mainly medicinal 'Fengdan' and 'Jianshi powder', of which the output of 'Fengdan' Danpi accounts for about 50% of the total output of Danpi in the country. Tongling, Bozhou, Anhui Province, Shaoyang, Hunan Province and other places are important Danpi production bases.
1.2 Re-examination of the oil industry
Since 2011, peony seed oil has been certified as a new oil crop by the Ministry of Health of the People's Republic of China, and the national standard of "Peony Seed Oil", which was officially implemented in May 2022, has brought the oil peony industry into the road of standardized development. Compared with other edible oils, the content of unsaturated fatty acids in peony seed oil can reach 92.26%, of which the content of α-linolenic acid is much higher than that of soybean oil, peanut oil, sunflower oil and olive oil, etc., and contains a certain amount of phytosterols, vitamin E and squalene, etc., which has incomparable advantages of traditional edible oils. At present, the two major oil peonies certified by the state are purple peony and 'Fengdan'. Compared with the purple spotted peony that grows in the alpine region, 'Fengdan' is native to Tongling, Anhui Province, and its seed yield is high and suitable for cultivation in most parts of China.
Table 1 Comparison of oil quality of peony seed oil with several edible oils %
The development of oil peony has been 10 years, and how much income has actually been brought to farmers in its main producing areas of Heze, Luoyang and Tongling? At the same time, the rapid development of this emerging industry of oil peony, the research group believes that it should be re-examined from the following aspects: First, the supply of excellent seedlings of oil peony is the bottleneck that restricts the development of the oil peony industry. If the seed seedling is raised for too long, there will be no income in the short term, which will seriously affect the income generation of enterprises and growers, and the seed seedling, oil quality and resistance are unknown after the seed seedlings grow, and they may not maintain the same biological traits as the female parent. Therefore, the development of rapid and efficient breeding technology will be a bottleneck problem to be solved urgently in the development of oil peony industry.
The advent of the genome map of 'Fengdan' will open up targeted molecular breeding of oil peony, which will effectively alleviate this problem. Secondly, the yield of oil peony, it is reported that the Yangtze River basin generally produces 400~500kg of 667m2, 300~400kg in the Yellow River basin, and 200~300kg in the Northwest Loess Plateau. The seed yield of peony in different producing areas is different, and the gap is very large, so it is necessary to explore an efficient cultivation mode suitable for local oil peony with high yield, stable yield and low cost. Thirdly, in terms of deep processing and utilization of oil peony, the development of oil peony industry can be promoted from many aspects, such as improving the antioxidant performance of peony seed oil, increasing the purification and industrialization of α-linolenic acid from seed oil, and optimizing the application of peony seed meal in animal husbandry feed.
Professor Li Yucai pointed out in the "Strategic Thinking of China's Oil Peony Project" that the selected and suitable for local planting conditions of excellent varieties will be provided to the majority of growers. For example, in the Jiangnan region, the oil can be combined with the ornamental industry, so that there are flowers to be appreciated and seeds can be harvested, and the peony cultivation technology suitable for the humid and hot climate conditions and cohesive paddy soil in the Jiangnan region can be promoted and demonstrated. Other regions can also adjust the planting strategy according to the actual situation.
1.3 'Fengdan' comprehensive industrial upgrading
In addition to medicinal and oil use, the application of 'Fengdan' has also been further expanded to ornamental, edible, health care and daily chemical aspects. The ornamental nature of 'Fengdan' is different, different from the peony flower with large color, graceful and luxurious characteristics, its flowers are single-petaled, most of them are white, the petal folds have an oil painting-like texture, noble and pure, and are called "oil painting peony" popular in the fresh cut flower market. The stamens and petals of 'Fengdan' can be reprocessed to form peony stamens, tea, peony flower cakes and other foods. Peony seed oil has health and skin care value. Relevant studies have shown that peony seed oil has the effect of lowering blood pressure, lowering blood lipids and improving Alzheimer's disease, and the unsaturated fatty acids in seed oil show significant effects on antioxidant, anti-free radical anti-aging and improving diabetes. Peony seed oil has a broad market prospect in daily chemical skin care and health care, with good ultraviolet absorption and burn repair properties, can better absorb UVA and UVB in the light, and has good sunscreen performance. Therefore, the 'Fengdan' industry has a wide range of uses, covering different life fields such as ornamental, medicinal, edible, health care and medical beauty, and its industrial application prospects are huge.
2 Factors influencing the growth and development of 'Fengdan'
2.1 Effects of environmental factors on the growth and development of 'Fengdan'
Environmental factors affect the growth, development and phenotypic traits of 'Fengdan'. The results showed that ecological factors had an important impact on the growth of 'Fengdan' and the accumulation of nutrients in seeds. The seed quality of 'Fengdan' was correlated with soil organic matter content, altitude, annual sunshine duration, average monthly temperature and annual rainfall, among which altitude had the greatest impact on seed phenotype. With the increase of altitude, the pods, grain weight, grain length and width of 'Fengdan' increased significantly, and the seed oil yield also increased, and further studies showed that altitude changes promoted the synthesis of oil by affecting the activity of acetyl-CoA carboxylase (ACCase) in the fatty acid synthesis pathway.
Light plays a very important role in the growth and development of plants, and appropriate light intensity can promote the overall growth of plants and the accumulation of plant photosynthetic products. 'Fengdan' is a long-day plant that likes light but is not resistant to long-term exposure. Different shading treatments showed that when the shading rate was 45%~60%, the net photosynthetic rate of 'Fengdan' was significantly higher than that of the non-shading and 75% shading treatments, and the photosynthetic performance of over-shading 'Fengdan' decreased significantly. Moderate shading could increase the yield of fruits and seeds of 'Fengdan', and the fruit biomass of 'Fengdan' increased by 6.8g · The yield of plant-1 increased by 341.7%, and the seed yield increased by nearly 4.0g·plant-1, the yield increased by nearly 389.3%. Planting density is an important factor in determining plant photosynthesis. The results showed that the appropriate planting density could improve the yield per plant, 100-seed weight and seed quality of 'Fengdan', while too small planting density would lead to insufficient light and longitudinal elongation of the plant. Reasonable shading methods and planting density can improve the light conditions, promote ventilation and light transmission, and then improve the growth and development of 'Fengdan' plants and seed yield.
Water plays a direct role in determining the growth and development of the fleshy root system of 'Fengdan'. The results showed that excessive water would have a serious adverse effect on the root system of 'Fengdan', and the root vigor index was only 2.34% of that of the non-flooded control after 168 h of flooding. The leaves, ground diameter and plant height of 'Fengdan' of different ages weakened to varying degrees after water shortage and water saturation stress. When the soil maintains a suitable relative water content, the water plays a good role in promoting the growth and development of 'Fengdan'. When the relative soil moisture content was 75%~80%, the morphology of 'Fengdan' seedlings was significantly increased compared with the control, among which the root activity increased by 12.57% and the number of roots and whiskers increased by 17.95%, while the taproot length, leaf area and biomass of 'Fengdan' decreased significantly under severe water shortage stress. In the actual production application, it is also necessary to monitor the water changes in the 'Fengdan' cultivation plot in real time, combined with the climatic conditions of the cultivation area, the watering frequency will increase if the rainfall is less, and the watering frequency should be reduced if the rainfall is more, and the drainage should be paid attention to to avoid water siltation.
2.2 Effect of cultivation medium on the growth and development of 'Fengdan'
Succulent root plants have high drainage requirements for the planting site, and excessive water accumulation will lead to weakened root vitality and respiration, and root rot will occur in severe cases. A single substrate is not conducive to the growth and development of peony, and the cultivation substrate improvement of peony mainly uses a mixture of multiple substrates to improve air permeability and drainage ability. The results showed that the mixed substrate with a ratio of 2∶2∶1 had good air permeability and drainage capacity, and the germination rate of 'Fengdan' was maintained at 85%~87%, which was significantly higher than that of other substrates. There is still a big gap in the research on the improvement of the cultivation substrate of 'Fengdan', and there is no standard to meet the needs of industrialization. According to the different industrial needs of medicinal 'Fengdan' or oil-used 'Fengdan', different refined matrix ratio standards are formulated.
In addition to the substrate ratio, the physical and chemical properties of the soil are extremely important for the growth of 'Fengdan'. It is generally believed that the pH tolerance range of 'Fengdan' is 6.5~8.0, which is closely related to soil depth and other soil indicators. The pH of shallow soil was significantly correlated with plant growth, and the EC value of middle soil was significantly correlated with plant growth and development. EC values at 500 μ S · 'Fengdan' was planted below cm-1, and the soil had no significant inhibitory effect on its growth, and the plant grew well. Therefore, before planting 'Fengdan', soil improvement should be carried out in combination with the substrate ratio and various factors in the soil, and the soil pH and EC value should be taken as important indicators to judge the growth environment of 'Fengdan', and targeted improvements should be carried out in combination with the specific conditions of the planting site.
3 Effects of nutrients on the growth and development of 'Fengdan'
Nitrogen, phosphorus and potassium are a large number of elements in the soil and a large number of life elements necessary for plant growth and development, and their effects on plants are multifaceted. Nitrogen is involved in most physiological and biochemical reactions in plants, and is an important part of proteins, chlorophyll and various enzymes in plants. The results showed that the uptake of a large number of elements in the annual growth of 'Fengdan' was different, and nitrogen was the element with the highest annual uptake. Nitrogen had a great influence on the photosynthesis of 'Fengdan', and its net photosynthetic rate and photosynthetic capacity increased with the increase of nitrogen application rate, and some studies showed that nitrogen was the primary factor for the increase of the yield of 'Fengdan', and higher nitrogen application rate could promote the increase of the yield of 'Fengdan'. The nitrogen application rate should be controlled within a reasonable range, and the imbalance of nitrogen supply will lead to the inhibition of the growth of 'Fengdan', and in severe cases, it will lead to a decrease in yield.
Phosphorus is an essential element for plant growth, which participates in the photosynthesis, respiration and growth process of plants, and affects the storage and transfer of plant energy. The supply of appropriate phosphorus can improve the photosynthetic performance of plants, high phosphorus and low phosphorus will affect the photosynthesis of plants, and in the case of severe phosphorus deficiency, it will affect the formation of photosynthetic products, and high phosphorus will cause toxic effects on plants, resulting in a decrease in photosynthetic rate. Previous studies have found that phosphorus is second only to nitrogen in its effect on the increase of production of 'Fengdan'.
Potassium acts as a catalyst for many enzymes in plants, enhancing photosynthesis, promoting protein synthesis, metabolism of sugars and fats, and enhancing plant stress resistance. During the annual growth and development of 'Fengdan', the uptake and utilization of potassium was related to the development period of the plant. The results showed that the potassium uptake of 'Fengdan' was much higher than that of nitrogen and phosphorus during the fruit development and grain maturity period, and the annual uptake was much higher than that of phosphorus, which was similar to that of nitrogen.
Throughout the annual growth and development period of 'Fengdan', its growth stages can be roughly divided into spring germination stage, leaf development stage, wind chime stage, full flowering stage, post-flowering and fruiting stage, grain maturity stage and autumn and winter dormancy stage. In the budding stage of 'Fengdan', most of the nitrogen, phosphorus and potassium elements are accumulated in the aboveground part and the content is the highest in the bud, and a large number of elements will move to the bud for vegetative growth, and a large number of elements in the plant change greatly, so it is necessary to replenish nutrients in time. After that, to the stage of the big wind chime, the elements began to gather to the leaves and flower buds, and the plants began to transition from vegetative growth to reproductive growth, which required a large amount of nutrients to ensure the blooming of flowers, and the absorption of nitrogen and phosphorus by 'Fengdan' was relatively high during this period, and a number of studies showed that the absorption of nitrogen by 'Fengdan' in this period was the highest, up to 1.01 g ·plant-1. During this period, the nutrient supplement should be mainly nitrogen, supplemented by phosphorus and potassium, and appropriately adjusted in combination with soil fertility. After the flowering period, the flow of the three macroelements in Fengdan' changed again, and a large number of elements gradually converged into the fruit. The absorption of phosphorus and potassium reached a high point during the fruiting stage of 'Fengdan', and the absorption of potassium reached the highest level in the whole year. Therefore, the nutritional supplement of 'Fengdan' fruit should be mainly potassium and phosphorus, supplemented by nitrogen. In the autumn and winter hibernation period, a large number of elements from various organs in the body of 'Fengdan' begin to transfer to the roots and stems to accumulate nutrients for the next cycle of growth. This period is also the active stage of root development and flower bud differentiation of peony, and the application rate of phosphorus can be appropriately increased on the basis of the balanced application of nitrogen, phosphorus and potassium to promote the development of peony roots.
The results showed that the ratio of nitrogen, phosphorus and potassium in the fertilizer applied to 'Fengdan' throughout the year should be 1∶0.35∶0.36 or 1∶0.35∶0.72, which could effectively promote the seed yield of 'Fengdan', but the fertilizer ratio of field planting in different regions was also related to soil nutrients, substrate selection and climate environment. We can learn from the absorption law of nitrogen, phosphorus and potassium elements in different periods of 'Fengdan', and apply fertilizer reasonably according to local conditions.
4 Cultivation and maintenance strategies of 'Fengdan'
As the saying goes, peony "three points of planting, seven points of nourishment". The planting and maintenance of peony is mainly divided into planting, fertilization, pruning and pest control, etc., 'Fengdan' as a resource plant with both medicinal oil concept, according to different uses, its cultivation and maintenance in fertilization, pruning and other aspects are slightly different.
4.1 Nutritional supplementation
Fertilization is the basic measure of crop production, and the amount of fertilizer and the different ratios of nutrients directly affect the growth and development of crops. The growth, flower shape, seed yield and quality of peony were affected by the amount of fertilizer and the ratio of nutrients. 'Fengdan' prefers a fertile soil environment, and the nutrient content of the soil in most of the main producing areas of Fengdan in the mainland cannot meet the demand standard in its natural state, so it is necessary to supplement nutrients when planting 'Fengdan'.
Before sowing seeds, 'Fengdan' needs to be deeply turned into the soil as the base fertilizer, and the leaves are sprayed with phosphorus and potassium fertilizer in March, September and November of the following year, the fertilizer application in the second and third years is the same as that of the first year, and the compound fertilizer is applied in each period on the basis of the fourth year, and compound fertilizer is used as the main fertilizer supply in the fifth year after the childhood. When applying fertilizer to transplanted seedlings, pay attention to giving enough time for the plant to rest and recover, try not to apply fertilizer in the year of transplanting to protect the root development and promote the plant's adaptation to the new environment, and then apply fertilizer in the following year. The fertilizer ratio was adjusted according to the differences in nutrient requirements at different development stages of the 'Fengdan' annual cycle. Nitrogen fertilizer and phosphorus fertilizer were applied to promote the overall growth and flowering of plants during the germination stage, more phosphorus and potassium fertilizers were applied after flowering to promote the development and ripening of fruits, and phosphorus fertilizer could be partially increased before the onset of dormancy period to promote the development of the root system of 'Fengdan'.
4.2 Stubble pruning
The plastic pruning of peony is generally divided into spring and autumn, and the rational use of artificial management measures such as budding and stubble pruning can effectively adjust the "source-reservoir" relationship of plants. Studies have shown that when the fruit ratio of camellia oleifera is 36:1 by pruning means, there will be no poor fruit growth in the next year. There are similar reports in 'Fengdan', and too many flower buds will increase the nutrient consumption of the aboveground parts of the 'Fengdan' plant, which will seriously affect the development of the plant. From the perspective of the entire 'Fengdan' industry, the oil and medicinal 'Fengdan' are completely different in terms of stubble pruning. Medicinal 'Fengdan' needs to remove all flower buds in the early flowering stage to promote the growth and development of roots and avoid the loss of plant nutrients to the reproductive organs, while oil 'Fengdan' needs to retain part of the flower buds. Different budding stages and methods had a significant impact on the growth and development of 'Fengdan' plants. The results showed that the longest flower stems of 'Fengdan' were significantly higher than those of the control when only 2/3 of the buds were cut off for each bud, and the flower stems increased significantly when the large wind bell stage and the flat peach stage were selected for bud thinning. This result may be related to the return of nutrients from the remaining flower buds into the flower stem. Autumn stubble can effectively promote the growth and development of 'Fengdan' plants in the following year. The results showed that stubble leveling treatment with reducing plant height and crown width of 'Fengdan' could significantly increase the number of branches of 'Fengdan' in the following year, and more nutrients were applied to the growth of new branches.
4.3 Pest and disease control
The pest control of 'Fengdan' needs to be carried out systematically and comprehensively, using different measures and means according to different development stages. The soil of the sowing or transplanting site needs to be fully turned so that it is fully exposed to sunlight to achieve soil disinfection and sterilization, and the soil is deeply insecticidal with spraying insecticides. After the flowering period to the fruit ripening stage, there is a high incidence period of various diseases, including leaf spot, root rot, etc. For leaf spot, you can apply Bordeaux liquid to spray the foliage, root rot can be turned over to dry the soil before the arrival of summer, and the soil and roots with germs must be removed as soon as possible after the infection is found, and other plants should be watered with ferrous sulfate solution to prevent infection. For insect pests, trichlorfon can be applied. The prevention and control of root rot should be paid attention to the medicinal 'Fengdan', and the control of various insect pests should be carried out during the fruit development period for the oil 'Fengdan'. On the whole, the prevention and control of 'Fengdan' pests and diseases is carried out according to the time and place in different development periods in the annual cycle, so as to focus on prevention and block the occurrence of pests and diseases.
5 Current problems and future prospects for the development of 'Fengdan' industry
At present, the 'Fengdan' industry has reached a certain scale, but there are still some development gaps in the closed-loop of the 'Fengdan' industrial chain. Based on the current development status, the research group believes that the following aspects need to be improved: firstly, the extraction method, storage conditions, and taste of 'Fengdan' seed oil make consumers less biased in their choice, and the higher market price and lagging publicity lead to a narrow market for peony seed oil. Secondly, the entire 'Fengdan' industry lacks a standardized and precise system.
Before the identification of oil peony as a new oil crop, the 'Fengdan' industry was mainly medicinal, and the yield of root danpi was taken as an important criterion for output value, but the oil industry needed to improve seed yield and oil yield. The demand for 'Fengdan' is different, and there are also differences in cultivation and maintenance models, coupled with factors such as indistinguishable planting modes and extensive management in production, which ultimately lead to the lack of intensification and industrialization of the industry. Thirdly, the combination of production, education and research in the 'Fengdan' industry is loose. At present, the main production areas of major oil peony varieties are relatively single, and there is still a lack of high-yield, stable yield and low-cost efficient cultivation system, and the existing technical reserves cannot meet the needs of the peony industry to the international market.
The development of the 'Fengdan' industry should take production as the main purpose, scientific cultivation as the core guidance, and R&D and publicity as the starting point, build a sustainable, replicable and promotable technical system, and form a closed-loop chain of the industry. Peony is a precious flower with historical and cultural heritage, and it is also a strategic resource plant with the same origin of medicine and food, with broad development space and huge market potential. At present, the cultivation of medicinal and oil 'Fengdan' in mainland China and its corresponding industry development are still in a relatively simple state, how to carry forward the peony culture and enhance the resource advantages of peony in the mainland, which needs to be carefully examined. Accelerate scientific research in the field of peony, eliminate various pain points and itches in the development of the industry, and promote the development of the industry.