Origin
Vigna maranguensis (Taub.) Harms is a wild plant that belongs to the genus Vigna, which is a member of the family Fabaceae. It is native to East Africa, specifically in the Usambara Mountains in Tanzania.
Common Names
The plant is commonly referred to as Marangu bean or Marangu groundnut due to its origin in the Marangu region of Tanzania. It is also known as the Usambara groundnut because of its occurrence in the Usambara Mountains in Tanzania.
Uses
The Marangu bean is traditionally used as food by the Chagga people who inhabit the Marangu region in Tanzania. The beans are boiled or roasted and consumed as a snack or a meal. They can also be used in making porridge or soup. The plant is also used as a livestock feed in some African countries.
General Appearance
Vigna maranguensis is a scrambling herbaceous plant that can reach up to 2 meters in length. It has a thin stem with tendrils that aid in anchoring it to other plants. The leaves are compound, with three leaflets that are ovate to elliptic in shape and have a velvety texture. The flowers are yellow and occur in racemes that arise from the leaf axils. The fruits are pods that are linear, flattish and have a length of 20-30 cm. The pods contain about 8 to 15 seeds that are flattened and are light brown or grey in color with dark blotches at the hilum.
Light Requirements
Vigna maranguensis (Taub.) Harms typically prefers partial shade, although it can also thrive in full sunlight. It is important to provide the plant with enough light to help with photosynthesis, but it should not be exposed to overly harsh direct sunlight, as this can cause the leaves to wilt or scorch. Indoor growers should ensure that their plants receive at least 6-8 hours of indirect light each day.
Temperature Requirements
Generally, Vigna maranguensis (Taub.) Harms prefers warm and humid conditions. Ideally, the plant should be grown in temperatures between 22°C and 32°C (72°F and 90°F), but can tolerate lower temperatures if they are not prolonged. It is important to keep the plant away from heat sources such as radiators or air conditioners, as this can cause stress or damage to the leaves.
Soil Requirements
Vigna maranguensis (Taub.) Harms requires well-draining soil that is rich in organic matter. The plant prefers a slightly acidic to neutral soil pH range of 5.5 to 7.5. It can be grown in a variety of soil types, including sandy, loamy, or clay soils, as long as they are well-draining and have adequate nutrients. The plant should also be fertilized regularly with a balanced, all-purpose fertilizer to support healthy growth and development.
Cultivation of Vigna maranguensis
Vigna maranguensis grows well in warm temperatures ranging from 25-30°C. It requires medium to heavy rainfall, with an ideal range between 800-1200 mm per annum. It grows in well-drained, rich soils with slightly acidic characteristics ranging from 6.0-6.5 pH.
Watering needs
Vigna maranguensis requires regular watering throughout its growth period. The frequency of watering should be determined by the prevailing weather conditions and soil moisture. Overwatering should be avoided as it can result in waterlogging, leading to the development of root rot.
Fertilization
Vigna maranguensis requires sufficient nitrogen and phosphorous for optimal growth. Incorporating organic fertilizer, such as animal waste, into the soil before planting improves soil fertility and nutrient retention. Nitrogenous fertilizers should be applied, especially during the flowering and podding stages, to encourage vigorous growth and high yields.
Pruning
Pruning is essential in maintaining the plant's vigor and health. Regular pruning encourages bushy growth and increases yield. It involves removing diseased and dead stems, topping, and thinning, which helps improve air circulation and sunlight penetration. Pruning after each harvest helps to reduce the incidences of fungal and bacterial infections.
Propagation of Vigna maranguensis
Vigna maranguensis is a legume plant that is native to Tanzania. It is primarily propagated through seeds. The seeds are easily obtainable and affordable, making propagation an easy process. However, Vigna maranguensis can also be propagated through cuttings and grafting.
Propagating through Seeds
The first step to propagate Vigna maranguensis through seeds is to identify mature pods on the plant. Mature pods are greenish-yellow in color and are fully grown. Once identified, the pod should be left on the plant to dry out further. When the pod is dry, it can be harvested by cutting the stem holding the pod with a pair of scissors.
The next step is to thresh the pod to remove the seeds from their pods. The seeds can then be cleaned and sorted to remove any dirt or debris. After cleaning, the seeds can be put in a container and stored in a cool, dry place until they are ready for planting. Planting should be done during the rainy season to ensure optimal growth.
Cuttings
Propagating Vigna maranguensis through cuttings involves cutting a section of the plant’s stem and planting it in soil to develop roots. To do this, cutting should be done during the plant's active growing season, which is typically the rainy season. Cuttings should be made from a healthy and matured plant.
After the cutting has been taken, it should be dipped in rooting hormones, which helps to foster root growth. The cutting should then be placed in a well-draining potting soil mix and placed in a warm and humid location. Care should be taken not to expose the cutting to direct sunlight to prevent heat stress.
Grafting
Grafting involves joining a Vigna maranguensis stem with another related species with a strong root system. The rootstock plant provides the newly grafted plant with nutrients and water while the scion plant provides the leaves, branches, and flowers of the new plant.
For grafting to be successful, it is essential to select a compatible rootstock plant. Once a compatible plant is identified, the stem of the scion should be cut an inch above its node. A V-cut should be made in the rootstock stem, and the cut portion of the scion should be inserted into the stem.
After the graft has been made, the newly grafted plant should be placed in a well-draining potting soil mix and placed in a warm and humid location. The graft should be checked regularly to ensure that it is healing and growing well.
Disease and Pest Management of Vigna maranguensis (Taub.) Harms
Vigna maranguensis, also known as the Marangu cowpea, is a legume species native to Africa. Like other plants, it is susceptible to various diseases and pests that can cause significant damage to the crop. To ensure optimal yield and plant health, proper disease and pest management measures should be implemented throughout the growing season.
Common Diseases
One of the common diseases that can affect Vigna maranguensis is the cowpea aphid-borne mosaic virus which is transmitted by aphids. This virus can cause stunted growth, leaf curling, and yellowing of leaves. Another disease is anthracnose, which is caused by the fungus Colletotrichum lindemuthianum. It causes dark lesions on the leaves, stems, and pods eventually leading to defoliation and loss of yield.
Disease Management
To manage virus diseases in Vigna maranguensis, control measures targeting the vector, aphids, should be implemented. This can be done through the use of insecticide sprays or the release of insect predators like ladybird beetles. For fungal diseases like anthracnose, crop rotation, weed management, and fungicide sprays can be used to manage the disease. Fungicide sprays should be used following proper safety measures, and a licensed pesticide applicator should conduct the spraying.
Common Pests
Vigna maranguensis can be attacked by various pests, including leafhoppers, thrips, and pod borers like the maruca pod borer. These pests can cause damage to the leaves, flowers, and pods, leading to reduced yield.
Pest Management
Effective pest management can be achieved using insecticides and cultural methods. Cultural methods include proper tillage practices, weed management, and planting resistant cultivars. Insecticide sprays should be used only when necessary and following the recommended guidelines. Integrated pest management (IPM) strategies should be used to minimize the impact of insecticides on non-target organisms while preserving their effectiveness.
Implementing proper disease and pest management measures is crucial for the proper growth and development of Vigna maranguensis. A proactive approach that combines cultural, chemical, and biological methods is the best way to ensure plant health and optimal yield.
