General Description
Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker, commonly known as the lesser Guinea yam or batoko-yaw, is a perennial climbing plant belonging to the family Dioscoreaceae. It is native to West Africa, particularly in Nigeria, where it is commonly cultivated by local communities for food and medicinal purposes.
Appearance
The plant has a tuberous root system that is cylindrical in shape and has a rough, scaly texture. The stems are slender, twining, and can reach up to 2-3 meters in length. The leaves are heart-shaped, alternate, and have a shiny green color. The plant produces small greenish-white flowers that have a distinct odor.
Uses
The tubers of Dioscorea praehensilis var. minutiflora are known for their edible and medicinal properties. They are rich in starch and vitamins and are used in various dishes in Nigeria as a staple food. The tubers are also believed to have medicinal properties and are used locally to treat various ailments, including stomach disorders, headache, and fever. The root is also used in Traditional African Medicine to prevent and manage diabetes, rheumatism, and hypertension.
The plant is also used as a green manure cover crop in agroforestry systems due to its nitrogen fixing properties. It is a good source of fodder for livestock and is also used in erosion control and soil improvement.
Growth Conditions for Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker
When it comes to the growth conditions for Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker, the following elements are essential:
Light
The plant prefers to grow in partial shade, with exposure to some sunlight. Direct exposure to sunlight can cause leaf scorching, while complete shade can affect the plant's growth and yield. Therefore, partial shade with a few hours of exposure to sunlight each day is ideal.
Temperature
The ideal temperature range for the plant's growth is between 25°C to 35°C. The plant requires warm temperatures to grow, but it cannot withstand extreme heat. The plant can be grown in tropical or subtropical regions, given suitable conditions for growth.
Soil Requirements
The plant thrives in loose, well-draining, and fertile soil. The soil pH level should be between 5.5 to 6.5, and it should contain adequate organic matter. The soil should be moist, but not waterlogged, and it should retain moisture for extended periods. The plant can also grow in a sandy loam or clay loam soil, given that it is rich in nutrients.
Cultivation Method
Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker, commonly known as the forest yam, is a climbing plant that is native to tropical Africa. The plant can grow up to 15 meters long, and it prefers warm, humid, and shady conditions. Therefore, when cultivating the plant, you should plant it in a warm and humid environment, but ensure that there is enough shade to protect it from direct sunlight.
Additionally, the plant grows best in well-drained soils. Therefore, ensure that you plant it in soils with good drainage and high organic matter content. The soil pH should range between 5.5 and 6.5, and the soil temperature should be between 24 and 32 degrees Celsius.
Watering Needs
The forest yam requires adequate water for optimal growth. You should water the plant regularly, especially during dry seasons, to keep the soil moist. However, avoid overwatering it as this can cause root rot. Water the plant when the soil is slightly dry about one inch deep.
Fertilization
The forest yam requires moderate fertilization to improve its growth and yield. Fertilize the plant with organic compost or well-rotted animal manure during the planting season. Additionally, you can apply NPK fertilizers with a ratio of 20:10:10 or 15:15:15 to the soil every three months.
Pruning
Pruning the forest yam is critical, especially when the plant begins to climb uncontrollably. Pruning helps to shape the plant, control its growth, and improve airflow, which reduces the risk of fungal infections. When pruning, remove dead or diseased leaves, stems, and vines. Additionally, you can cut the plant's branches to a length of about 1.8 meters to encourage the sprouting of new branches.
Propagation of Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker
Propagation is the process of creating new plants from existing ones. There are several methods of propagating Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker:
Seed propagation
The most common and easiest way to propagate Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker is through seed propagation. The seeds should be sown in a well-drained potting mix, covered with a thin layer of soil and kept moist at all times. The best temperature for germination is between 25°C and 30°C. The seeds should germinate within 2 to 4 weeks.
Vegetative propagation
Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker can also be propagated vegetatively. This method involves taking cuttings or dividing the parent plant. Take cuttings of 10 to 12 cm from the parent plant's stems, making sure each cutting has a few leaves. Place the cutting in a well-drained potting mix and water it regularly. The cuttings should root within a few weeks. When dividing the parent plant, use a sharp, sterile knife to divide the tubers, making sure each division has a good root system.
Air layering
Air layering is another propagation method that can be used for Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker. Air layering involves wounding a stem and applying a rooting hormone to encourage roots to grow. After rooting, the rooted section is cut off and planted in a container filled with a well-draining soil mix. This method takes longer than others, as the rooting process can take several months.
Disease Management
Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker is prone to several diseases that can reduce its yield and quality. Here are some of the most common diseases and ways to manage them:
Black spots
Black spots are caused by the fungus Colletotrichum gloeosporioides. They appear as round, black lesions on the leaves and stems. To manage black spots, the affected parts should be removed and burned to prevent further spread of the fungus. Fungicides containing azoxystrobin, chlorothalonil, or mancozeb can also be applied to control the disease. However, it is important to follow the recommended dosage and frequency to avoid pesticide residues on the plant and the environment.
Anthracnose
Anthracnose is another fungal disease that affects Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker. It often begins as yellow or brown spots on the leaves and eventually leads to premature defoliation. To manage anthracnose, regular pruning and removal of infected parts can help reduce the spread of the disease. Application of fungicides such as copper-based products or tebuconazole can also be effective against anthracnose.
Pest Management
Aside from diseases, Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker is also vulnerable to pest attacks. Here are some common pests and ways to manage them:
Mites
Mites are small arthropods that suck the sap of the plant, causing yellowing and disfiguration of the leaves. To manage mites, neem oil or insecticidal soap can be sprayed on the plant to suffocate and repel them. Application of predatory mites such as Phytoseiulus persimilis can also help control the pest population without harming the plant.
Root-knot nematodes
Root-knot nematodes are microscopic worms that invade the plant's roots and cause swelling and galling. They can weaken and stunt the growth of Dioscorea praehensilis Benth. var. minutiflora (Engl.) Baker. To manage root-knot nematodes, crop rotation and soil solarization can be conducted to reduce the population of the pest. Application of nematicides such as 1,3-dichloropropene and metam sodium can also be effective but should be handled with caution due to their toxicity.
