Overview of Dioscorea dumetorum (Kunth) Pax
Dioscorea dumetorum, also known as Bitter yam, Africa arrowroot, or Bush yam, is a perennial plant that belongs to the family Dioscoreaceae. The plant is native to West African countries, such as Cameroon, Ivory Coast, Nigeria, and Ghana.
Description of Dioscorea dumetorum (Kunth) Pax
The Dioscorea dumetorum plant has a vine-like appearance, and it can climb up to 10 meters in height. The leaves are heart-shaped, large, and dark green in color. The plant produces small, greenish-white flowers, which develop into a capsule containing black seeds. The yam tuber of the plant is cylindrical or elongated and can grow up to 60 cm in length and 25 cm in diameter. The skin of the yam is rough, and the flesh is white, but it turns yellow after cooking.
Uses of Dioscorea dumetorum (Kunth) Pax
The bitter yam is a staple food in many West African countries, where it is used to make several traditional dishes. The tuber can be boiled, roasted, or fried, and can also be used to make flour for baking. The yam is a rich source of carbohydrates and dietary fiber, and it is also a good source of Vitamins B6 and C. Besides its food uses, the plant also has some medicinal properties. The bark, roots, and leaves of the plant are used in traditional medicine to treat various ailments such as fever, dysentery, and gonorrhea.
Moreover, Dioscorea dumetorum is an essential plant in agroforestry systems, and it is used in soil conservation programs. The plant is drought-resistant and can thrive in harsh environmental conditions, making it an ideal crop for farmers in arid and semi-arid regions.
Light Requirements
Dioscorea dumetorum requires partial to full sunlight to grow well. It is intolerant to complete shade, which may stunt its growth or even kill the plant.
Temperature Needs
The plant grows well under tropical to subtropical climatic conditions, preferring temperatures between 22°C to 32°C. It is sensitive to cold and frost, and exposure to extremely low temperatures can lead to stunted growth or death of the plant.
Soil Conditions
Dioscorea dumetorum grows best in well-drained sandy loam, sandy clay loam, or clay loam soils. The soil should be moderately fertile, with a pH ranging between 5.5 and 7.5. The optimal soil temperature for growth is between 25°C and 30°C.
Cultivation Methods
Dioscorea dumetorum, also known as bush yam, is a perennial vine that thrives in warm and humid climates with temperatures ranging from 25 to 35 degrees Celsius. This plant prefers well-drained soils that are rich in organic matter, and it grows best in areas with partial to full sunlight exposure. The propagation of this plant can be achieved through the use of stem cuttings or seedlings. The stem cuttings should be taken from mature and healthy plants and planted in a nursery bed until they establish roots. Seedlings should be transplanted into the soil after they have grown to a height of about 15 to 20 centimeters.
Watering Needs
Dioscorea dumetorum requires even and regular watering to thrive. The plant should be irrigated at intervals of 2 to 3 days, depending on the prevailing weather conditions. During dry spells, the plant requires more frequent watering to avoid wilting. Overwatering should be avoided as it can lead to root rot and damage the plant.
Fertilization
Fertilization is necessary to maintain the health and productivity of Dioscorea dumetorum. The application of organic fertilizers such as well-rotted manure and compost should be done during the planting stage and at appropriate intervals thereafter. Nitrogen-rich fertilizers can also be applied during the vegetative growth stage to promote the growth of foliage and stem development. Fertilizers should be applied in small quantities, and only as necessary, to avoid the buildup of excessive nutrients in the soil.
Pruning
Pruning may be necessary to keep Dioscorea dumetorum under control and minimize the spread of the plant. Pruning should be done during the vegetative growth stage to remove weak and diseased stems, leaving only the strong and healthy ones. This encourages the plant's growth and productivity and also improves the quality of the yams produced. Pruning should be carried out using disinfected pruning tools to prevent the spread of diseases.
Propagation of Dioscorea dumetorum (Kunth) Pax
Dioscorea dumetorum or Bitter yam is propagated in different ways, including:
Seed propagation
The plant produces seeds, which can be used for propagation. However, the germination rate is typically low, and the seedlings grow slowly.
Cuttings
Bitter yam can also be propagated by using stem cuttings. Cuttings should be taken from healthy and disease-free plants. They should be at least 15 cm long and have several nodes. Cuttings should be planted in a well-drained soil mixture of compost and sand or perlite.
Tubers
A faster and more straightforward method of propagating Dioscorea dumetorum is by using the tubers. The plant produces tubers underground, which can be dug up and cut into small pieces. Each piece should have at least one bud. These pieces are then planted in well-drained soil with a mixture of compost and sand or perlite. The tubers should be planted 10-15 cm deep.
Regardless of the propagation method used, it is essential to ensure that the young plants are protected from direct sunlight and excessive heat. They should be gradually exposed to outdoor conditions after they have grown to a reasonable size, and it is relatively safe to transplant them to their permanent location.
Disease and Pest Management for Dioscorea dumetorum (Kunth) Pax
Dioscorea dumetorum (Kunth) Pax, commonly known as bitter yam or bitter-leaf yam, is a tropical tuber crop that is widely grown in West and Central Africa. Like all crops, this plant is vulnerable to various diseases and pests which can reduce yields and affect the quality of the tubers. Proper disease and pest management is therefore crucial for a successful harvest.
Common Diseases
The most common diseases that affect Dioscorea dumetorum include anthracnose, black rot, and yam mosaic virus.
Anthracnose: This disease is caused by the fungus Colletotrichum gloeosporioides and is characterized by dark, sunken lesions on the leaves and stems. To manage anthracnose, remove and destroy infected plant parts and apply a fungicide to protect healthy plants.
Black Rot: This disease is caused by the fungus Lasiodiplodia theobromae and is characterized by dark, sunken lesions on the tubers which eventually turn black and become soft. To manage black rot, remove and destroy infected plant parts and avoid planting in waterlogged soils which favor fungal growth.
Yam Mosaic Virus: This disease is caused by a virus and is characterized by yellowing and mottling of the leaves. There is no cure for yam mosaic virus, so prevention is key. Plant disease-free seed yams and control the aphids which spread the virus.
Common Pests
The most common pests that affect Dioscorea dumetorum include yam beetles, nematodes, and rodents.
Yam Beetles: These insects feed on the leaves and stems of the plant, and can cause significant damage if left unchecked. To manage yam beetles, handpick and destroy adults and larvae and apply an insecticide if necessary.
Nematodes: These microscopic worms feed on the roots of the plant, causing stunted growth and reduced yields. To manage nematodes, rotate crops and plant resistant varieties, and apply organic soil amendments such as compost to improve soil health.
Rodents: These pests can cause significant damage by feeding on the tubers. To manage rodents, control weed growth around the plants which can provide hiding places for rodents, and use traps or baits to reduce their numbers.
By implementing proper disease and pest management strategies, farmers can protect their Dioscorea dumetorum crops and ensure a successful harvest.
