Overview
Dioscorea dawei De Wild. is a perennial plant that belongs to the family Dioscoreaceae. It is also known by various common names including Davi’s yam, edible yam, and anome oies. The plant is typically found in tropical regions of Africa including Cameroon, Congo, Guinea, and Nigeria.
Appearance
The plant typically grows up to 3 meters in height with cylindrical and elongated stems that can reach up to 2 cm in diameter. The stems of Dioscorea dawei De Wild. are glabrous and have a striated surface that ranges in color from brown to gray. The plant is characterized by its heart-shaped leaves that range in size from10-25cm in length and 6-20cm in width. The plant’s flowers are unisexual and grow in axillary spikes that are about 40cm in length.
Uses
Various parts of the plant have been utilized for medicinal, nutritional, and industrial purposes. For instance, the tuberous roots (yam) are nutritious and are used for culinary purposes to prepare soups and stews. The roots are also used in traditional medicine to treat various ailments like skin infections, hypertension, and arthritis. The leaves of the plant are used as a green vegetable in some African countries and they contain high levels of ascorbic acid, carotenoids, and antioxidants. Furthermore, the plant’s stem contains bioactive compounds like diosgenin that are used in the production of steroid drugs.
Cultivation
Dioscorea dawei De Wild. is propagated using vegetative methods like tuber cuttings, stem cuttings, and plant residues. The plant grows best in hot, humid, and well-drained soils that are rich in organic matter. It is typically grown as an intercrop with other crops like maize, cassava, and beans. In addition, the plant’s growth can be enhanced by the application of organic and inorganic fertilizers.
Conclusion
Dioscorea dawei De Wild. is a valuable plant that has various uses in society. Its nutritional, medicinal, and industrial benefits make it an indispensable plant in most African countries. The plant’s tuberous roots are nutritious, the leaves are a good source of vitamins, and the stem contains bioactive compounds with immense medicinal benefits. Its cultivation can be enhanced by the application of organic and inorganic fertilizers. With continued research, the plant has the potential to revolutionize the agricultural and pharmaceutical industries.
Growth Conditions for Dioscorea dawei De Wild.
Light Requirements: Dioscorea dawei De Wild. prefers a partially shaded to a shaded environment. Direct sunlight exposure can be harmful to the plant's growth and development.
Temperature: This plant grows well in a warm and humid environment. The ideal temperature range for this plant is between 20°C to 30°C (68°F to 86°F). Temperatures above or below this range can affect its growth and development.
Soil Requirements: The plant prefers a well-drained, slightly acidic to neutral soil. The soil should have a pH level between 5.5 to 7.0. The soil should be rich in organic matter and nutrients to support the plant's growth. The plant can also grow in sandy or loamy soil types.
Water Requirements: Dioscorea dawei De Wild. requires consistent moisture in the soil to thrive. The soil should not be waterlogged, but it should not dry out completely either. The best way to ensure consistent moisture is to water the plant regularly in small amounts.
Fertilizer Requirements: Fertilizing the plant can enhance its growth and development. The best option is to use organic fertilizers that provide essential macronutrients such as nitrogen, phosphorus, and potassium. Apply the fertilizer during the growing season in small amounts.
Cultivation Methods for Dioscorea Dawei De Wild.
Dioscorea dawei De Wild., commonly known as Dawei yam, is a plant that thrives in warm and humid environments. To cultivate it successfully, you need to take the following steps:
- Choose a planting site with well-draining soil, and that receives at least six hours of sunlight daily.
- Prepare the planting bed using a combination of organic matter and inorganic fertilizers.
- Plough the field to a depth of 30 cm and form ridges at intervals of 20 cm in rows 35-40 cm apart.
- Cut yam minisetts, (basic seedlings for propagation) from mature yams and leave them to dry for at least three days before planting.
- Plant the minisetts 10-15 cm deep on top of each ridge, leaving two or three buds above ground level.
- Cover the planting bed with a straw mulch will help the soil retain moisture and protect the plants from direct sunlight.
- Water the seedlings promptly after planting and maintain a regular watering schedule.
- Train the yam vines up sticks or trellises, so they don't sprawl on the ground.
- Weed your yam at least once every three weeks to prevent competition for nutrients and water.
Watering requirements for Dioscorea Dawei De Wild.
Dioscorea Dawei De Wild. needs consistent watering to thrive. It is essential to:
- Water your yam twice a week in the absence of rainfall.
- Avoid over-watering as it may increase the risk of fungal disease and plant decay.
- Use a watering can or drip irrigation system to ensure that the water goes directly to the roots without flooding the soil or leaves.
- Regularly check the moisture levels in the soil to adjust your watering schedule accordingly.
Fertilization of Dioscorea Dawei De Wild.
Proper fertilization is necessary for the healthy growth of the yam plant. Use the following fertilization guidelines:
- Apply a balanced fertilizer, such as N.P.K (Nitrogen, Phosphorus, and Potassium) fertilizer at planting time; this will provide nutrients to the planting beds and, in turn, the growing yams.
- Once the plants have started to emerge, top-dress them with 50g of urea (carbamide) for every 10sq.m, taking care not to apply the urea too close to the yam plant's stalk as it may cause burn and decay of the stems.
- Another option is to use organic fertilizers, such as compost, animal manure, and bone meal. These fertilizers should be well-composted to avoid adding pathogens to your garden soil.
- Fertilize only when necessary; over-fertilization can lead to excess foliage and a low yield of roots.
Pruning of Dioscorea Dawei De Wild.
Pruning helps to control the size of the vines and minimize congestion, making your yam garden easier to manage. Here's how to prune:
- Wait until your yam vines reach a height of 30cm then cut off the plant's growing tip; this will stimulate new lateral growth.
- Remove any dead or diseased foliage that you observe.
- Pinch off any side shoots that emerge from the leaf axils to encourage the plant to produce bigger, healthier foliage that can provide more support to the yam fruit.
- Trim out any shoots that penetrate the trellis mesh or spread too far from the plant.
Propagation of Dioscorea Dawei De Wild.
The propagation of Dioscorea Dawei De Wild. can be done either sexually or asexually.
Sexual Propagation
In sexual propagation, the plant is propagated through seeds. The seeds are collected from the fruits of the plant when they are fully matured. The mature seeds are sown in well-drained soil in a warm, humid environment. The seeds will take around 2-3 weeks to germinate. Once the plant has developed a strong and healthy root system, it can be transplanted to its permanent location.
Asexual Propagation
In asexual propagation, the plant is propagated through division and vegetative propagation.
Division: In division, the underground tuber of the plant is carefully divided into smaller pieces with a sharp, sterilized knife. Each division should have some intact roots and at least one dormant bud. The divisions are planted in a prepared soil mixture, and it takes around 4-6 weeks for the new plant to establish.
Vegetative Propagation: In vegetative propagation, stem cuttings are taken from the parent plant. The cuttings are around 30cm long and should be taken during the plant's growing season. The cuttings are treated with a rooting hormone powder and planted in well-prepared soil. It takes around 3-4 weeks for the plant to develop roots and begin to grow.
Propagation of Dioscorea Dawei De Wild. can be done throughout the year under the correct conditions, and a combination of both sexual and asexual propagation can be used to achieve the desired plant numbers quickly and efficiently.
Disease and Pest Management for Dioscorea Dawei De Wild.
Dioscorea dawei De Wild. is a tropical plant that can be affected by several diseases and pests, affecting its growth and productivity. The following are some of the common diseases and pests of Dioscorea dawei and measures to control or manage them.
Diseases
Anthracnose - This is a fungal disease that causes leaf spots, stem lesions, and rotting of tubers. It is prevalent in high humidity and warm conditions. To manage this disease, cultural practices such as crop rotation and removal of infected plant debris are essential. Fungicides like copper-based products and mancozeb can also be applied.
Virus diseases - Dioscorea dawei is susceptible to several viral pathogens that cause stunted growth, leaf mottling, and yellowing. These viruses are usually transmitted by aphids and other sap-sucking insects. The best way to manage viral diseases is through controlling the insect vectors. Using insecticides like imidacloprid and neonicotinoids can limit aphid populations and virus spread.
Black rot- This is another bacterial disease that causes blackening of stems and tubers. The disease is prevalent in warm, wet conditions. To manage black rot, cultural practices like crop rotation and avoiding overhead irrigation are necessary. Copper-based fungicides or biological agents such as Bacillus subtilis can also limit the spread of the disease.
Pests
Yam beetle - This is a significant pest that feeds on the leaves, shoots, and stems of the plant, leading to stunted growth and even death. To manage the yam beetle, cultural practices like handpicking and destroying the beetles are essential. Insecticides like carbaryl and pyrethroids can also be used.
Mites - Mites are sap-sucking pests that cause yellowing and distortion of leaves. They can be controlled biologically by the use of predatory mites such as Amblyseius cucumeris. Insecticides like neem oil and acaricides such as abamectin are also effective in reducing mite populations.
Root-knot nematode - This is a soil-borne pest that causes root galls, stunted growth, and reduced yields. The best way to manage this pest is through crop rotation and using nematode-resistant varieties. Nematicides like carbofuran and oxamyl can also be used to manage root-knot nematodes.
In conclusion, controlling diseases and pests in Dioscorea dawei De Wild. is critical to ensure optimal growth and yield. Incorporating cultural practices such as crop rotation and removing infected plant debris are essential. Chemical control measures such as the use of insecticides and fungicides are also important in managing disease and pest populations.
