Difficult requirements and countermeasures for planting Platycodon grandiflorum flowers?

Difficult requirements and countermeasures for planting Platycodon grandiflorum flowers?

Platycodon grandiflorum (Eustoma grandiflorumShinn.) It is a herbaceous flower of Platycodon grandiflorum of Gentianaceae, also known as Texas orchid, Ribao and prairie gentian. it is native to the limestone-rich grassland desert of Nebraska, Colorado to Texas in the central United States. Platycodon grandiflorum flowers are rich in shape and color, and have a long vase period. At present, they are the mainstream flowers for weddings. In recent years, varieties continue to push through the old and bring forth the new, especially rose-shaped varieties occupy the mainstream of the market, which makes consumption expand rapidly. recently, varieties in the shape of carnations and lilies have been selected, and the future market development should not be underestimated.

Platycodon grandiflorum is the fastest growing cut flower species in the world in the past 20 years. As early as 2001, the annual production of cut flowers in Japan has reached 129 million, ranking fourth among cut flowers in terms of sales. Sales in Europe also reached 122 million, making it one of the top 10 cut flowers. At present, according to the estimation of seed and seedling sales, the annual output of Yunnan Province in China is about 200 million branches, with an annual growth rate of more than 15%, which has risen to the fourth place among the main cut flowers.

Platycodon grandiflorum is recognized as one of the most difficult flowers in the world. Once there are problems in the planting process, either the quality drops sharply, or a large number of plants die and the yield is seriously reduced. In the process of planting Platycodon grandiflorum, the main problems that are easy to appear can be summarized as 6 aspects, which can also be said to be under traditional cultivation conditions. Six major difficulties are: (1) the seeds are small, the seedling raising cycle is long and difficult; (2) sensitive to all kinds of adversity and prone to rosette dormancy, resulting in a great extension of production time; (3) sensitive to high temperature and long sunshine, short stem flowering and quality decline in summer and autumn; (4) high precision of water and fertilizer management. no matter the careless management of large seedlings and small seedlings can easily lead to dead seedlings or poor growth; (5) there are many kinds of soil-borne diseases and the speed of continuous cropping obstacles is fast. (6) there are many leaf diseases and insect pests represented by downy mildew, so it is difficult to manage plant protection. The editor analyzes various difficult problems in order to have a deeper understanding and understanding of the planting technology of Platycodon grandiflorum, turn difficulties into easy, and promote the sustainable development of Platycodon grandiflorum planting industry.

1 raising seedlings

1.1 difficulties in raising seedlings

Platycodon grandiflorum is the only seed propagation species among the top 10 cut flowers in the world. The seeds of Platycodon grandiflorum are very small, each seed is only 0.00005 g, it carries little nutrition and grows slowly in the early stage, so the seedling period of the seeds is as long as 3 months. Collecting F1 hybrid seeds is still the only way of reproduction, and there is no successful commercial mode of asexual reproduction at home and abroad. Both tissue culture and cutting propagation can form seedlings and blossom, but there are still some problems to be overcome. Platycodon grandiflorum has the saying of "seedling half-cropping", which means that once a high-quality seedling is produced, the cultivation has been half successful. Platycodon grandiflorum seedlings is a highly technical work, but also depends on highly self-control facilities, excellent environmental control and fine management. Although some flower farmers raise their own seedlings, they are no longer common, relying more on professional seedling companies, and even a large number of them are imported from the Netherlands.

1.2 Seedling requirements

Platycodon grandiflorum seedlings generally use 200 ~ 860 hole plates as seedling trays and light substrates such as imported peat, vermiculite and perlite as seedling substrates. Modern equipment and facilities such as seed cold storage, precision seeder, automatic greenhouse, self-propelled watering truck, wet curtain cooling and artificial light replenishment are needed, and the investment cost is high. Platycodon grandiflorum needs the natural process of "raising seedlings at low temperature and flowering at high temperature". Even with the above mechanical equipment, it also needs cold climate, strict light, temperature, water, fertilizer and humidity and other production conditions control and mature experience and technology. Improper management and substandard conditions in the production process can easily lead to problems such as rosette seeding, carrying diseases and insect pests, short-stem flowering, weak disease resistance and so on.

2 rosette dormancy

2.1 factors leading to dormancy

The wild characteristics of Platycodon grandiflorum show that the rosette phenomenon is a growth state caused by adverse environment, and it is a way to survive the difficult environment through long-term evolution. Rosette dormancy may occur in Platycodon grandiflorum at seedling stage, planting stage, stubble changing stage, and even bolting and flowering stage. In addition to the main factors of rosette dormancy, there are drought, root cutting, drying, strong light, the use of mature seeds at high temperature, genetic characteristics of varieties and so on. In the process of artificial cultivation of Platycodon grandiflorum, if the rosette phenomenon occurs, the cultivation time will be greatly prolonged, resulting in a serious reduction in yield. After the rosette formation of the plant, the leaves are dense, and the greenhouse management is lack of experience, resulting in a low-temperature and humid environment, which often leads to the outbreak of downy mildew, and even leads to no harvest in extreme cases.

2.2 relationship between temperature and dormancy

Platycodon grandiflorum seedlings are very sensitive to temperature in seedling stage, and adult temperature also has a decisive effect on its growth and development. Temperature is the main factor leading to rosettization. When the night temperature is 15 ℃ and the temperature is 25 ℃, the quality of cut Platycodon grandiflorum is the best. When the average temperature is below 10 ℃, the growth of Platycodon grandiflorum almost stops. When the night temperature is lower than 8 ℃, most late or very late varieties grow slowly and are prone to rosette dormancy caused by low temperature, and the flowering time can be delayed by 3 ~ 4 months. When the night temperature is higher than 23 ℃, most Platycodon grandiflorum varieties are prone to rosette dormancy caused by high temperature, and sometimes they will not wake up until the spring of the second year, and the production delay can be more than half a year.

2.3 methods to avoid rosette dormancy of Platycodon grandiflorum

The main results are as follows: (1) raising seedlings with cool temperature: the rosette can be avoided by raising seedlings at 23 ℃ day and night after sowing, or the seedlings can be raised by 10 ℃ when 2 ~ 4 pairs of leaves are raised. The rosette phenomenon can be broken after 30 days. (2) do not use seeds harvested at a high temperature (33 ℃ day and night). (3) at the initial stage of planting, adverse environmental factors such as strong light, high temperature and water shortage should be avoided. (4) raise seedlings with point plate to avoid root injury during transplantation, and pay attention to water management so as not to make the seedlings aging. (5) choose varieties that are born early or have less demand for low temperature. (6) when the night temperature is 15 ~ 17 ℃ in the high temperature season, rosette will not occur even if the day temperature reaches 30 ~ 33 ℃.

3 short stem flowering

3.1 occurrence period

In the absence of heating and cooling equipment, it is difficult to bloom in winter, and short-stem flowering in summer and autumn is easy to be encountered in the production of Platycodon grandiflorum. Generally speaking, early-maturing varieties bloom early in winter and spring, but short-stem flowering is easy to occur in summer, and buds may appear when they are 20 cm high. It is necessary to repeatedly pick buds or hearts in order to prolong the branch length and make it barely qualified. It is difficult for late-maturing varieties to bloom in winter and early spring, but the phenomenon of short-stem flowering is rare in summer and autumn. If there are two crops of annual production in this way, it will be more difficult to take into account the quality.

3.2 causes of occurrence

The flowering response of Platycodon grandiflorum belongs to relatively long-day crops with cumulative quantity, that is, it blossoms early under long sunshine and high temperature, but the plant height is relatively short and the number of flowers is less. On the contrary, Platycodon grandiflorum can blossom in short days, but it blossoms later, the plant height is higher and the number of flowers is more. The induction period of Platycodon grandiflorum to the day length and temperature of flower bud differentiation is about 45 ~ 80 days after sowing, and when the true leaves are 2 ~ 3 pairs, when they encounter high temperature and long sunshine, it is easy to advance flower bud differentiation and cause short stems to blossom after planting. It is also easy to cause short stem flowering when the sunshine is long and the average temperature is higher than 20 ℃ after planting. At the suitable growth temperature, the longer the sunshine time is, the earlier the flower bud differentiation is and the earlier the flowering is, but the shorter the branch length is, the less the branch number is, and the less the flower number on the same flower is. According to Japanese research, Platycodon grandiflorum can achieve flower bud differentiation when the daily length is more than 10.5 hours. Under the condition of 15 ℃ night temperature, the flowering period of 16 h day length treatment of the same variety was about 2 months earlier than that of 8 h short day treatment.

Platycodon grandiflorum is sensitive to water shortage after planting. Insufficient water supply will result in small growth and high soil EC value, resulting in poor nutrition absorption, root damage, and short stem flowering.

3.3 solution

In order to solve the problem of short-stem flowering and rosette dormancy of Platycodon grandiflorum, and to realize high-quality annual production, the editor has four suggestions, which are to carry out production only in low-latitude plateau climate, to reduce seed cost, to raise seedlings at cool temperature and to adopt black screen. China has summer high temperature period except Yunnan and other low latitude plateau climate regions and northern cold regions, so it is not suitable for the annual production of Platycodon grandiflorum. In order to ensure quality and facilitate management, foreign Platycodon grandiflorum production generally produces only one crop of flowers per seedling, while in China, it is expensive to rely on imported seeds, and the cost can only be recovered by producing two crops of flowers with one seedling. The climate of the Netherlands is cold every year, raising more than 200 million seedlings every year, and it is also supplied to China, Israel and Africa. The use of shading and heat preservation facilities can keep heat in winter and reduce day length in summer, which is a good way to improve output and quality at the same time.

4 Water and fertilizer management and soil-borne diseases

4.1 importance of water and fertilizer management

Platycodon grandiflorum is an exotic plant, which is very different from the wild semi-arid environment under artificial cultivation conditions. Platycodon grandiflorum is sensitive to water supply, insufficient supply will lead to growth stagnation, excessive supply will lead to a serious decline in soil permeability, breeding diseases, resulting in lack of ponds. During the whole growth period, the demand for water was high in the front and low in the second, and gradually decreased. That is, adequate irrigation should be given before and 1 week after planting to maintain high soil water content. Once the root system grows and gradually extends downward, attention should be paid to gradually reduce soil water content and increase soil air permeability. No matter in which growth period, too much water may cause the direct death of Platycodon grandiflorum, and accompanied by a variety of soil-borne diseases spread or breed in the soil, leaving hidden dangers.

4.2 causes of high incidence of soil-borne diseases

Platycodon grandiflorum has no resistance to most soil-borne diseases, Fusarium, Botrytis cinerea, Phytophthora, Phytophthora, etc. can cause a large number of missing ponds, while root-knot nematodes are easy to cause severe poor growth and other fungal diseases. Generally, flower growers use cauliflower rotation to plant Platycodon grandiflorum, and the continuous planting is generally no more than one year. According to the author's microscopic observation and field investigation, Fusarium oxysporum is the most common soil-borne disease. at present, Fusarium species resistant to Fusarium oxysporum have been selected in Japan, which has greatly reduced the lack of ponds, but the growth potential of resistant plants has been observed to decline significantly, and after the evolution of pathogens, resistant varieties may become non-resistant varieties. Therefore, soil disinfection is still important. Root-knot nematodes are also common under the conditions of lack of flood-drought rotation and soil disinfection, and the disease is urgent, which can cause harm in the first crop. When the source of cultivated land is surface water without disinfection measures, the possibility of transmission of various soil-borne pathogens through irrigation is also greatly increased.

5 continuous cropping obstacle

5.1 main causes of continuous cropping obstacles

The main manifestations of continuous cropping obstacles of Platycodon grandiflorum are high incidence of soil-borne diseases, thin plant growth, yellowing of old leaves, root yellowing, necrosis and so on. The continuous cropping obstacle of Platycodon grandiflorum can be caused by the accumulation of soil-borne pathogens and nematodes in the soil, especially when there is a large number of missing ponds in the previous crop. Soil consolidation, high EC value and high content of toxic ions such as sodium and chloride ions are also important reasons. Japanese studies have shown that Platycodon grandiflorum is more sensitive to EC in sandy soil than in clayey soil. The EC value of soil measured by 1 ∶ 5 of two kinds of soil and water and the survival status of flowers and seedlings after planting in sandy soil showed that the EC value of all plants survived in sandy soil was less than 1.0 ds/m, when the EC value was more than 1.0 ds/m, some plants died, and all plants above 1.9 ds/m died. The EC value of the whole plant survival in clayey soil was the same as that in sandy soil, which was less than 1.0 ds/m, and the EC value was more than... Some of the plants withered at 1.0 ds/m, and all the plants above 2.8 ds/m died.

Foreign studies have shown that the accumulation of allelochemicals produced by Platycodon grandiflorum during planting is also an important cause of continuous cropping obstacles. The cultivation of Platycodon grandiflorum in the Netherlands adopts the model of producing one cut flower with one seed and harvests 5 crops a year. Whether there are a large number of missing ponds or not, the soil is sterilized by high temperature steam before each planting, and one of its purposes is to remove allelochemicals accumulated in the soil at high temperature.

5.2 solution proposal

Continuous cropping obstacles occur in many horticultural crops, but are more prominent in Platycodon grandiflorum. This is closely related to the traditional mode of production, such as irrigation water carrying pathogens, lack of scientific soil testing and fertilization methods leading to rapid deterioration of soil physical and chemical properties, excessive use of fungicidal pesticides to irrigate roots to reduce the number of probiotics in the soil. and the increase of resistant pathogens and so on. The cost of steam disinfection for continuous cropping obstacles is too high, and the degree of realization is low in China, while the chemical disinfection of Mianlong and Wei Baimu also has the problems of high cost and unstable effectiveness. Flower growers through crop rotation is a more ecological and environmentally friendly way, but there are obvious problems of economic benefits and unstable production. International experience shows that continuous cropping obstacles cannot be solved by a single agronomic measure, and we must adopt a multi-pronged approach, comprehensive prevention and control, and rely on scientific and technological innovation and the popularization and application of new technologies. In recent years, gratifying progress has been made in eco-friendly disinfection methods such as solar energy, biomass, lime nitrogen combined with flooding, which should be vigorously studied and popularized in China.

6 diseases and insect pests on the ground

The main pests of Platycodon grandiflorum are Noctuidae pests, thrips, whitefly, red spiders, Liriomyza huidobrensis and so on. Other pests such as aphids, grubs and slugs also occur from time to time. Some insect pests are not only difficult to control and high cost of medication, but also the key is that the seedlings of Platycodon grandiflorum infection quickly cause virus disease, the whole plant appears mosaic, yellowing, deformity and other symptoms, can not bloom and sell normally.

The main diseases of Platycodon grandiflorum are downy mildew, gray mildew, powdery mildew and so on, which are similar to most greenhouse flower crops, but its special feature is that not only the leaves are damaged, but also the plants are more likely to die. When Platycodon grandiflorum was infected with downy mildew in seedling stage, its growth stagnated and died gradually. After infection in the initial stage of colonization, the growth stagnated, and the growth was poor after repeated infection after spray control, and the yield could not be formed. Platycodon grandiflorum is in the prosperous period after bolting, and the plant will die because the soil is moist and closed and the rhizome is infected with Botrytis cinerea. Platycodon grandiflorum is easy to be infected with downy mildew and Botrytis cinerea when it meets the environmental conditions of low temperature and high humidity in the greenhouse at night. Platycodon grandiflorum is native to the dry and rainless grasslands, and it likes to be cool and dry. The suitable air humidity for growth is between 50% and 75%. Because the environment of low temperature and humidity and high temperature and humidity are easy to appear in the heating greenhouse, which is very different from the original place, the possibility of Platycodon grandiflorum infection is greatly increased.

7 Comprehensive solution

The difficulties in the above six aspects are the problems faced by Platycodon grandiflorum under the traditional production mode, which hinders the expansion of the production of Platycodon grandiflorum. The general spraying and fertilization measures can not solve the above problems. Taking downy mildew as an example, downy mildew is a serious disease in the planting process of Platycodon grandiflorum in Tonghai area of Yunnan Province. the key cause of the disease is the decrease of air temperature at night and the continuous precipitation of gaseous water in the high temperature air. condensed water is formed on the leaves, which is most likely to spread in the small seedling stage of moist soil and the harvest period of dense plants, which can not be controlled simply by spraying. The best and fundamental solution is to prevent leaf condensation by adding mild heat preservation measures.

In short, Platycodon grandiflorum has broad market prospects and great potential. With the continuous rise of labor prices, the traditional mode of production has great risks and unstable benefits, which has reached the time of transformation and upgrading. In order to develop the new production of Platycodon grandiflorum, we should follow the requirements of industrialization and intensification of modern flower production and follow the concept of scientific and technological innovation and ecological environmental protection. It is necessary to comprehensively consider the dialectical relationship among pathogens, hosts and environment that restrict and promote each other, and take into account the ecological factors such as light, temperature and humidity, soil fertilizer and water, disease and caterpillar fungus to design the production system, through standardized, specialized and large-scale planting, it is possible to obtain stable income and achieve sustainable development.

Difficult requirements and countermeasures for planting Platycodon grandiflorum flowers?