Overview
Dioscorea triphylla A.Rich. var. rotundata R.Knuth is a plant species that belongs to the family Dioscoreaceae. It is commonly known as yam and is widely cultivated in different parts of the world due to its many uses in food and medicine production.
Origin and Distribution
The plant is believed to have originated from West Africa and has been introduced to different parts of the world, including Asia and America. Today, it is widely cultivated in tropical regions around the world, with Nigeria being the largest producer of yams.
Common Names
In addition to yam, the plant is also commonly known by several other names, including ñame, igname, djambi, and air potato. Different varieties of yam exist, including the white yam, yellow yam, and Chinese yam.
General Appearance
The Dioscorea triphylla A.Rich. var. rotundata R.Knuth yam plant grows as a vine, with its foliage consisting of three large, heart-shaped leaves. The plant produces underground tubers that are typically cylindrical or oblong in shape and can vary in size, with some very large specimens weighing over 50 kg. The tubers have a rough, scaly texture and a brownish or white skin, with a white or yellowish flesh inside.
Uses
The yam is an important food crop in many cultures, with the tubers being used to produce various different dishes, including mashed yam, yam fries, and yam porridge. The plant is also used in traditional medicine, with yam extracts being used to treat a range of ailments, including asthma, diabetes, and arthritis. In addition to this, the plant has been found to have potential for use in industrial applications, such as the production of bioethanol and biodegradable plastics.
Growth conditions for Dioscorea triphylla A.Rich. var. rotundata R.Knuth:
Light requirements: Dioscorea triphylla A.Rich. var. rotundata R.Knuth thrives in bright, filtered light. It requires at least 50% shade to grow and develop properly. Direct sunlight can harm the plant and cause its leaves to burn.
Temperature requirements: This plant prefers warm temperatures between 20°C to 30°C. While it can tolerate lower temperatures, it cannot endure frost and should not be grown in areas where temperature regularly drops below 5°C. It is also essential to protect the plant from cold drafts and winds.
Soil requirements: The soil should be well-drained and loamy, with a pH between 5.0 to 6.5. It is essential to avoid waterlogged soils as it can cause the plant to rot. Adding organic matter to the soil can improve its water retention capabilities while also providing the necessary nutrients to the plant.
Fertilizer requirements: The plant requires regular fertilization throughout the growing season. Fertilizers with a high content of nitrogen are best suited for Dioscorea triphylla A.Rich. var. rotundata R.Knuth. However, it is essential to avoid over-fertilization as it can burn the roots and damage the plant.
Water requirements: The plant requires consistent watering to ensure proper growth. It should be watered regularly, ensuring that the soil remains moist but not waterlogged. The frequency of watering may increase during the hot and dry season. It is essential to avoid overhead watering as it can cause the plant to develop diseases.
Propagation: Dioscorea triphylla A.Rich. var. rotundata R.Knuth can be propagated through rhizomes, bulbs or division. The plants can also be grown from seeds in well-drained soil. The seeds should be soaked in water before planting, and it may take up to four weeks for the plant to germinate.
Cultivation
The plant Dioscorea triphylla A.Rich. var. rotundata R.Knuth, also known as the white yam or Guinea yam, is a tropical root crop that is commonly cultivated for its edible tubers. The plant can be grown in a variety of soils, but it prefers well-drained loamy soils that are rich in organic matter. It is also important to choose a growing site that receives plenty of sunlight.
Propagation can be done with either stem cuttings or tubers. If using stem cuttings, make sure they are taken from healthy plants and are at least 30cm long. Plant the cuttings in a prepared bed and make sure they are watered regularly until they root and start to grow.
Watering Needs
The white yam plant requires adequate water to produce good yields. Ideally, the plants should be watered deeply once or twice a week or more frequently if the weather is dry. Overwatering, however, should be avoided as this can lead to root rot and other diseases.
Fertilization
Since yam is a heavy feeder, it is important to apply fertilizers regularly to ensure proper growth and development. A balanced fertilizer with a 15:15:15 NPK ratio is recommended. Apply the fertilizer at least twice during the growing season. Organic fertilizer can also be used to improve soil fertility and promote healthy growth.
Pruning
Pruning is not necessary for the white yam plant, but it can help to promote better air circulation and control the spread of diseases. If pruning is done, it should be carried out early in the season when the plants are still young. This will encourage branching and promote the production of tubers.
Propagation of Dioscorea triphylla A.Rich. var. rotundata R.Knuth
Dioscorea triphylla A.Rich. var. rotundata R.Knuth, commonly known as the roundleaf yam, can be propagated through both vegetative and sexual means. The plant belongs to the Dioscoreaceae family and is native to South America.
Vegetative Propagation
One of the most common methods of propagating Dioscorea triphylla A.Rich. var. rotundata R.Knuth is through vegetative propagation. This process involves using cuttings or sections of the stem or tuber to grow new plants. The cuttings should be taken when the plant is dormant and should be at least 10 cm long. While cutting the stem or tuber, care should be taken to ensure that no damage is caused to the parent plant.
The cuttings should be treated with fungicide and left to dry for a day or two before being planted. The ideal time for planting cuttings is in early spring. The cuttings should be planted in pots filled with a well-draining potting mix. The pots should be kept in a warm, humid place until the new plants emerge.
Sexual Propagation
Dioscorea triphylla A.Rich. var. rotundata R.Knuth can also be propagated through sexual means. The plant produces male and female flowers on separate plants. The flowers of the plant are insect-pollinated, and once fertilization occurs, seeds are produced.
The best time to collect the seeds is after the fruit has ripened and turned yellow. The fruit should be cleaned and soaked in water for a day or two to remove any remaining pulp. The seeds should be stored in a cool, dry place until they are ready to be planted.
The seeds should be planted in pots filled with a well-draining potting mix. The pots should be kept in a warm, humid place until the new plants emerge. The seedlings should be transplanted into larger pots or directly into the ground once they have grown large enough.
Disease and Pest Management for Dioscorea triphylla A.Rich. var. rotundata R.Knuth
Dioscorea triphylla A.Rich. var. rotundata R.Knuth, commonly known as yam, is vulnerable to a variety of diseases and pests. Disease and pest management is essential to ensure healthy and productive yam crops.
Common Diseases
1. Anthracnose: It is a fungal disease that causes black spots on leaves and stems, leading to defoliation and stunted growth. To manage the disease, apply a copper-based fungicide to the whole plant. 2. Bacterial wilt: This disease causes wilting and yellowing of leaves. Infected tubers also have brown streaks. The disease spreads through the soil. To manage bacterial wilt, dig up and dispose of infected plants. 3. Yam mosaic virus: It is a viral disease that causes yellow mottling, stunted growth, and deformed leaves. There is no cure for viral diseases. Therefore, removing infected plants is the only management option.
Common Pests
1. Yam beetles: These pests feed on leaves, stems, and tubers, reducing the yield. To manage the beetles, handpick them from the plants regularly. 2. Yam nematode: It is a microscopic worm that feeds on yam roots, causing swellings and reducing plant growth. To manage nematodes, rotate crops regularly and use resistant varieties. 3. Cutworms: These pests chew through young yam plants, causing them to wilt and die. To manage cutworms, apply Bacillus thuringiensis-based insecticides to the soil around the plants.
Regular crop inspection and hygiene practices, such as cleaning tools and equipment, can also help prevent disease and pest infestation.
