Overview of Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège, commonly known as the white yam, is a tropical root vegetable that belongs to the family Dioscoreaceae. It is one of the most important yam species in West Africa, where it is primarily cultivated for its starchy tubers.
Origin and Distribution
The white yam is native to West Africa, specifically in the region stretching from Senegal to Cameroon. Today, it is widely grown in various African countries, including Nigeria, Ghana, and Ivory Coast. It has also been introduced in other tropical regions around the world, such as the Caribbean, South America, and Southeast Asia.
Uses
The main use of the white yam is as a food crop. Its starchy tubers are harvested and processed into different food products, such as yam flour, pounded yam, and yam chips. The tubers are boiled, roasted, or fried and are often served as a staple food alongside soup, stew, or sauce. In addition to its culinary uses, the white yam has also been used in traditional medicine to treat various ailments, such as cough, asthma, and rheumatism.
General Appearance
The white yam is a herbaceous vine that can reach up to 10 meters in length. It has heart-shaped leaves that are arranged alternately on the stem. The plant produces bulbous tubers that can weigh up to 30 kg and have a white, creamy flesh. The tubers have a rough, scaly bark-like skin that is often peeled off before consumption.
The white yam is a hardy and versatile crop that can be grown in a range of soils and climates. It is an important source of food and income for many farmers in West Africa and continues to be a staple food in the region's culinary tradition.
Light Requirements
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège requires full sunlight exposure for optimal growth and development. Inadequate light can result in stunted growth, less foliage, and poor tuber formation. Therefore, it is important to grow the plant in areas with high light availability or under artificial lighting during cloudy or low light conditions.
Temperature Requirements
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège thrives in tropical to subtropical climates with warm and humid conditions. The ideal temperature range for optimal growth and yield is between 25 to 35°C (77-95°F). Temperatures below 20°C can slow down plant growth and delay the maturity of tubers. The plant can tolerate occasional slight frosts but can suffer significant yield loss at prolonged low temperatures.
Soil Requirements
The plant grows best in well-drained and fertile soils with good water retention capacity. Dark sandy loam and clay soils are ideal provided they are well-drained and have good water retention ability. The pH range of the soil should be between 5.5 to 6.5, though the plant can tolerate slightly acidic to slightly alkaline soils. Soil fertility is important, and application of compost manure or other organic matter to the soil prior to planting can help in achieving optimal growth and yield.
Cultivation Methods
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège, commonly known as "white yam," can grow in a variety of soils, including sandy loam, clay loam, and sandy soil. The plant prefers tropical and subtropical climates with temperatures between 25 - 30°C. It can be propagated through vine cuttings or by planting whole small yam tubers.
Watering Needs
The plant requires consistent and adequate moisture levels, and therefore you should provide regular watering throughout the growing season. White yams require more water in the beginning stages but need a bit of a dry spell two weeks before harvesting. Overwatering can lead to root rot, so ensure you do not leave the soil waterlogged.
Fertilization
White yams require fertile soil to grow well. You can provide organic fertilizers like farmyard manure or compost to the soil before planting. You can also apply inorganic fertilizers rich in nitrogen to encourage vine growth. A nitrogen application rate of around 40:20:20 kg NPK per hectare spread in two splits should be enough for yam plants.
Pruning
White yams can produce a vast amount of foliage and vines that require pruning. Pruning generally involves removing dead leaves, diseased areas, and removing long sprawling vines that would limit growth. You should also cut back the vines to avoid spreading to other plants, as they can quickly grow out of control. Prune regularly for the plant to have room for air circulation and sunlight exposure.
Propagation of Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège, commonly known as white yam, is a tropical plant highly valued for its edible tubers. Propagation of this plant can be done through various methods, including:
Seed propagation
This species produces seeds, which can be collected and used for propagation. However, seed propagation is not commonly used due to the low germination rate and the difficulty in identifying the gender of the plant as it takes time to flower.
Tuber propagation
The most common propagation method is through the use of tubers. Yam tubers are commonly used for planting, and they can be obtained from fields or markets if available. It is important to select healthy and disease-free tubers which are active and have buds or 'eyes'.
To propagate, the tubers are simply cut into sections, each with at least one bud or 'eye'. These sections are then planted in soil at a depth of around 8-10 cm. After planting, the soil should be kept moist and a steady temperature of around 25-30°C is required for optimal growth and germination.
Vine cutting propagation
Propagation can also be done by using vine cuttings. These are taken from mature vines and planted into the soil or another growing medium. The cuttings must be at least 30 cm long and should be planted at a depth of around 10-15 cm. These cuttings need to be watered regularly to ensure they do not dry out, and they require warm conditions for growth and development.
Propagation of Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège can be quite successful using any of these methods, and with proper care, new plants can grow and thrive in tropical areas.
Disease and Pest Management for Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège
Dioscorea cayenensis Lam. subsp. rotundata (Poir.) J.Miège, commonly known as white yam, is a staple food crop in many tropical regions around the world. As with all crops, it is susceptible to a range of diseases and pests that can affect its growth and yield. In this section, we will discuss some common diseases and pests that might affect the plant and suggest ways to manage them.
Common Diseases
One of the most common diseases affecting white yam is anthracnose, which is caused by the fungus Colletotrichum gloeosporioides. Symptoms of anthracnose include brown or black spots on the leaves, stems, and fruits of the plant. The spots may also become sunken and surrounded by a yellow halo. To manage anthracnose, it is important to practice good sanitation by removing and destroying infected plant parts. Applying fungicides such as copper-based products can also be effective in controlling the disease.
Another disease that can affect white yam is yam mosaic virus (YMV), which is transmitted by aphids. YMV causes yellowing and mottling of the leaves, stunting of plant growth, and reduced yields. To manage YMV, it is important to control the populations of aphids that transmit the virus by using insecticides and practicing good crop hygiene.
Common Pests
The most common pest that affects white yam is the yam tuber moth (Scrobipalpula absoluta), which burrows into the yam tubers and causes damage that can lead to secondary fungal and bacterial infections. Signs of infestation include small holes in the tubers, tunnels, and frass. To manage the yam tuber moth, it is important to practice good hygiene by removing and destroying infested tubers. Additionally, planting resistant varieties and applying insecticides can be effective pest management strategies.
Another pest that can affect white yam is the sweet potato weevil (Cylas spp.), which feeds on the stems and leaves of the plant and can cause significant damage to the crop. Signs of infestation include wilting, yellowing, and stunting of the plant. To manage the sweet potato weevil, it is important to rotate crops and remove and destroy infested plant parts. Additionally, applying insecticides and using pheromone traps can be effective control measures.
In conclusion, managing diseases and pests is crucial to maintaining healthy and productive white yam crops. Good sanitation practices, crop hygiene, rotation, and the use of resistant varieties, fungicides, and insecticides can all help prevent and control damage to the plant. Regular monitoring and early detection of diseases and pests can also be helpful in preventing the spread of infestations.
