1. Name of the plant
1.1. Scientific name: Artemisia annua Linn. (2n=18)
(Family: Asteraceae)
1.2. Local name: Sweet wormwood / Annual wormwood / Sweet annie / Sweet Sagewort (English); Qinghao / Huag hua hao (Chinese); Seeme davana (Kannada)
2. Plant part used in artemisinin / aromatic oil extraction
Whole herb at full bloom stage
3. Characteristics of the plant
A. annua is an annual, branched, erect herb with a very slender stem having a sweet aromatic odour. Its stems are deeply grooved. Leaves are bi- or tri- pinnatifid, linear or lanceolate. The flower heads are yellow, 2 mm in diameter, arranged in loose very slender panicle racemes. The fruit of A. annua is an achene with a single seed
inside. The seeds are approximately 1 mm in length, oblong, yellow-brownish with a lustrous surface marked by vertical furrows; seed endosperm is creamy white and contains fat content.
T he main constituent of the plant is artemisinin, which is obtained from the aerial parts of the plant and varies from 0.05-0.17% with an average of 0.1%. It is a promising anti-malarial drug effective against Plasmodium vivax and P. falciparum. The distillation of aerial parts of the plant also yield essential oil (0.2 – 0.4%) which comprised of many chemical constituents with the major compounds including myrcene (3.8%), 1,8-cineole (5.5%), artemisia ketone (66.7%), linalool (3.4%), camphor (0.6%), alpha-pinene (0.032%), (0.047%), ß-pinene (0.882%), borneol (0.2%) and ß-caryophyllene (1.2%). The essential oil is used in perfumery, cosmetics, dermatology and also has fungicidal properties.
4. Major production areas
A. annua is widely distributed in the temperate, cool temperate and subtropical zones (mainly in Asia) of the world. It is originated from China and grows mainly in the Middle, Eastern and Southern parts of Europe and the Northern, Middle and Eastern parts of Asia. In India, it is cultivated in medium to low-temperature conditions in Kashmir valley and hills of Himachal Pradesh and also in Uttar Pradesh to a limited scale.
5. Characteristics of strain(s) for cultivation
Artemisia is a large, diverse genus of plants, consisting of between 200 and 400 species comprises of mostly herbaceous plants and shrubs, which are known for the powerful chemical constituents in their essential oils. Artemisia genus includes notable species like A. vulgaris (Common mugwort), A. tridentata (Big sagebrush), A. annua (Sagewort), A. absinthum (Worm wood), A. dracunculus (Tarragon) and A. abrotanum (Southern wood). Most species have strong aromas, and bitter tastes from terpenoids and sesquiterpene lactones, which exist as an adaptation to discourage herbivores A. annua is a highly cross-pollinated crop. Hence, the crop exhibits large variation in maturity, leaf biomass yield and ‘artemisinin’ content. Many recently released varieties like Asha, Jeevanraksha, Suraksha and Cim-Arogya are recommended for commercial cultivation.
6. Cultivation methods
6.1 Soil
A. annua is adapted to a wide range of soil types from sandy loam to loamy soil which is free from water logging. However, a well-drained light loam soil rich in organic matter is best for its cultivation. It can be cultivated in a wide pH range of 4.5 to 8.5.
6.2 Climate
I t is a short-day, temperate plant, which requires cold winter and moderate summer. The critical photoperiod lies between 12 and 16 hours (average 13:31 hours). It can also be cultivated in subtropical areas as a winter crop. However, it has been found that the `artemisinin’ content is higher in plants grown in cooler climate compared to sub-tropical climate. Shading and higher temperature reduce the artemisinin content.
6.3 Propagation
A. annua is usually propagated by seeds. The good quality seeds are always filled up and have a shape. The seeds can be stored for an average period of 4 months if the water content is less than 13%. Cultivars with optimal growth characteristics are selected for seed collection. The seeds which do not have a dormant phase can be used in the same year or the following year. It is better to procure the seeds from reliable sources. Due to small seed size, direct sowing in the main field does not give good results. Hence, seedlings are first raised in nursery beds and then transplanted to the main field.
Nursery raising of seedlings
Nursery beds of convenient size are prepared, and well-decomposed FYM/compost at the rate of 10 kg per bed is applied. Further, 250- 500 g seeds (sufficient to raise seedlings for one hectare) are mixed with sand, spread uniformly over the nursery beds and covered with a thin layer of soil or sand. The beds are kept moist by frequent watering with the help of sprinkler or rose can. Seeds germinate in about 5-8 days. Freshly collected seeds germinate quickly, and the germination percentage is also high. The seedlings would be ready for transplanting after 6-8 weeks.
6.4 Land preparation
The land is ploughed 2-3 times to produce a fine tilth before the seedlings are transplanted. For better management, the land is laid into beds of convenient size after applying the recommended dose of manures and fertilizers.
6.5 Planting time
The crop can be grown in two different seasons under Indian conditions, the first crop during the late rainy season and the second during summer. Seeds can be sown in the nursery during September- October for the late rainy season crop and during November – December for the summer crop. For seed production, the rainy season sown crop is advisable, whereas, November – December planted crop is reported to give maximum oil yield.
6.6 Transplanting
The beds have to be irrigated a day before transplanting. The seedlings which are 6-8 weeks old, healthy and uniform should be transplanted at a spacing of 30-60 cm between rows and 45-60 cm between the plants. However, planting at a spacing of 45 × 45 cm is the best to obtain maximum biomass, essential oil and artemisinin yield. Usually transplanting is done in the evening hours to avoid transplantation shock. The plots are given light irrigation after transplanting. Gap filling should be done within 8-10 days of transplanting. It is advisable to plant two seedlings per hill to avoid seedling mortality.
6.7 Crop nutrition
T he crop responds well to the application of manures and fertilizers. Well, decomposed farm yard manure/compost should be to be applied at 10 t/ha before planting. A fertilizer dose of 60-80 kg N; 40-60 kg P2O5 and 60 kg K2O/ha may be applied depending upon the soil condition for getting a good yield. A full dose of P2O5 and K2O and two third dose of N are incorporated into the soil at the time of land preparation. The remaining one-third dose of N is applied in two equal split doses at 30 and 60 days after transplanting. A. annua is highly sensitive to the boron and iron deficiency. Hence, basal application of borax at the rate of 8 kg/ha is recommended. While, increased supply of copper, manganese and zinc are reported to cause an inhibitory effect on the crop by reducing its growth and artemisinin content.
6.8 Irrigation
The field is to be frequently irrigated from transplanting to the establishment of the crop. After establishment, only 3-4 irrigations will be required up to harvest period. Apply mulch to conserve soil moisture. However, irrigation should be discontinued 7-10 days before harvesting.
6.9 Intercultural operation
A. annua is sensitive to water logging, and it causes root rotting. In the rainy season, the channels and furrows should regularly be cleared. Keeping the crop weed-free during the early period of the establishment is essential to get a good harvest. The crop requires 2-3 weeding and hoeing during the growth period. The first inter-tillage and weeding should be done about 20 days after transplantation. The second weeding is needed before the major branching stage, followed by hilling. No inter-tillage weeding is necessary once the field is entirely covered by the plant. Manage weeds before they start competing with the main crop for nutrients and light. Use mulch to maintain moisture in the soil and to inhibit the growth of weeds. Do not use chemical herbicides to eradicate weeds.
6.10 Plant protection
Insect pests
1.Aphids: Aphids suck sap from young leaves and shoots and can be seen on the lower side of leaves.
Management: Spraying Azadirachtin 10,000 ppm @ 5 ml/l is effective to control the pest.
2.Ants: Ants attack plants mostly during seedling stage which leads to the withering and complete death of the plant. Management: Its menace can be minimized by mixing 10 kg of 1.5% chlorpyriphos per hectare into the soil at the time of land preparation
Diseases
1.Leaf blight: The disease is more common on mature plants of more than 50 days old. Within a plant usually, the older leaves are first affected by the disease. The initial symptom is the appearance of minute, brown lesions on the leaf tip. Later these lesions enlarge toward the middle and lamina of the leaves gradually turn yellowish. As the spots grew in size, the leaves often curled upward. Once the necrotic area covers the majority of the leaf lamina, the leaf shows a blighted appearance. In cases of severe infection, small branches and inflorescences also become blighted. Management: The disease can be controlled by spraying of Bordeaux
mixture 1%.
2.Damping off: The disease usually occurs in young seedlings which rot, collapse and die rapidly. Management: Disease can be overcome by adjusting the planting time, to get bright weather during the early stages of the establishment of the crop.
3.Root rot: The typical symptoms of this disease is withering of the whole plant. Later root turns black and rotting occurs.Management: Increase organic matter content in the soil, remove sick plants and apply Trichoderma to that site; follow crop rotation.
Viral diseases: In virus affected plants new leaves appear wrinkled and shrunken and have reduced leaf size Management: For managing viral disease control the aphids which are the vectors by spraying botanical pesticide [Azadirachtin 1% (10,000 ppm) @ 5 ml/l].
6.12 Harvesting
The crop is ready for harvesting in 4.5 – 5 months after transplanting. Although the content of artemisinin is affected by numerous factors such as geographical conditions, harvesting time, temperature and fertilizer application, harvesting time is critically important to ensure the optimum content of artemisinin in A. annua. The crop is to be harvested at full bloom stage, as harvesting at this stage recorded the maximum herb yield, essential oil and artemisinin content. Delayed harvest before flowering results in a low yield of artemisinin as well as essential oil. The crop is harvested by cutting the plants with a sickle at 15-30 cm above the ground level.
Harvest the crop in dry weather or during the hottest part of the day. Do not harvest when it is raining, or early in the morning when there is dew on the ground. The intermittent/multi harvesting of early planted full grown crops leads to relatively large sized leaf mass at the expense of stem mass and thereby resulted in high yield of artemisinin. Further, experiments also show that A. annua crop is suitable for ratooning with intermittent harvests at four times viz., 77, 132, 186 and 216 days after transplanting. It gives more yield of artemisinin than those harvested only once, twice or thrice.
6.12 Processing
Post-harvest processing is usually the most critical stage in determining the end quality of the aromatic plant material. Transport the harvested plant parts for processing as quickly as possible. Protect the plants from heat and rain during transportation. The post-harvest practices of A. annua include drying of herbage (leaves and thin stems) under ambient conditions; separation of and storage of herbage in moisture proof containers/packages. The adoption of multi-harvesting will allow spread of post-harvest operations over many months and extraction of the herbage in batches of convenient volume. The harvested crop needs to be dried to about 5-10% moisture content before its chemical extraction.
While the crops harvested in the summer (May/June) and winter (October / November) seasons can be economically shade dried, but those harvested in the rainy season (July September) may require the use of specially aerated drying chambers/suitable alternate equipment, making the post-harvest drying process relatively expensive. After the drying process is over, the leaves, flowers and thin stems are separated from the stalks. The essential oil from the fresh or dried leaves and flowers can be extracted by steam distillation or by solvent extraction methods using hexane as a solvent.
Distillation unit should be clean, rust free and free of any other odour. The essential oil obtained after distillation is then decanted and filtered. The distilled oil is treated with anhydrous sodium sulphate or common salt at the rate of 20 g/litre to remove the moisture. The oil should be stored in sealed amber coloured glass bottles or containers made of stainless steel, galvanised tanks, aluminium containers and stored in a cool and dry place.
6.13. Expected yield
Artemisia produces fresh herbage yield of about 10-15 t/ha which in turn gives 30-40 kg of essential oil per hectare. The essential oil content generally varies from 0.2-0.4%, which is found to be generally higher (0.34%) in early sown crop (September) and it decreases in late sown crop. The essential oil content is highest in the inflorescence compared to leaves. Similarly, the artemisinin content is found to be highest during anthesis and declines after flowering. The flowers contain 2-4 folds higher concentration of artemisinin compared to leaves.
7. The major chemical constituents
The main chemical constituents of A. annua are sesquiterpenoids, including artemisinin I, artemisinin II, artemisinin III, artemisinin IV, artemisinin V, artemisic acid, artemisilactone, artemisinol and epoxyarteannuinic acid. Besides, A. annua also consists of volatile and non-volatile constituents. The volatile components are mainly responsible for its essential oils with content being 0.2-0.25%. The main compounds, which account for about 70% of the essential oils, appear to be camphene, β-camphene, iso-artemisia ketone, 1-camphor, β-caryophyllene and β-pinene. In addition, other minor ingredients, such as artemisia ketone, 1,8-cineole, camphene hydrate, and cuminal are also found in the volatile parts of A. annual. The main non-volatile ingredients include sesquiterpenoids, flavonoids and coumarins, together with proteins (such as β-galactosidase, β-glucosidase) and steroids (e.g. β-sitosterol and stigmasterol).
Source-
- Directorate of Medicinal and Aromatic Plant Research
