Irvingia gabonensis

Dika
Ogbono nuts
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Malpighiales
Family:	Irvingiaceae
Genus:	Irvingia
Species:	I. gabonensis
Binomial name
Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill.
Natural occurrence of Irvingia gabonensis in Africa

Irvingia gabonensis is a species of African trees in the genus Irvingia, sometimes known by the common names wild mango, African mango, bush mango, dika or ogbono. They bear edible mango-like fruits, and are especially valued for their fat- and protein-rich nuts.

Distribution and habitat

Irvingia gabonensis is indigenous to the humid forest zone from the northern tip of Angola, including Congo, DR Congo, Nigeria, Côte d'Ivoire and south-western Uganda.^[1][2]

It is planted in parts of this area, e.g. in southeastern and south-western Nigeria and southern Cameroon, and also in Côte d'Ivoire, Ghana, Togo and Benin.

Biophysical limits

The tree is present in the tropical wet and dry climate zone.^[3] Dika grows naturally in canopied jungle, gallery forests and semi-deciduous forests. It grows at altitudes from 200–500 m with annual rainfalls from 1200–1500 mm.^[1] Supported temperature ranges from 20° to 38 °C under slightly shaded to very bright, clear skies. Deep soils with more than 150 centimetres (59 in) are needed with a moderate fertility and good drainage. pH can range from 4.5 to 7.5.

Description

Irvingia gabonensis grows straight, up to a height of 40 metres (130 ft) and 1 metre (3 ft 3 in) in diameter.^[1] It has buttresses to a height of 3 metres (9.8 ft). The outer bark is smooth to scaly with grey to yellow-grey color. The crown is evergreen, spherical and dense. Leaves are elliptic, one margin is often a little rounder than the other, acuminate, dark green and glossy on the upside. Flowers are yellow to greenish-white in small panicles.^[1] The flowers are bisexual. The fruit is nearly spherical, green when ripe with a bright orange pulp. The stone is woody and contains one seed. Seedling germinates epigeally.^[1]

Ecology

Irvingia gabonensis is pollinated by Coleoptera, Diptera, Hymenoptera and Lepidoptera.^[1] It flowers from March to June and has two fruiting seasons: from April to July and from September to October.^[2] Seeds are dispersed by specialized vertebrates as elephants and gorillas. By reducing the number of those animals, the spread and regeneration of dika decreases and it becomes dependent on human planting.^[4]

Cultivation

Until some years ago, 90% of dika products were harvested from scattered, wild trees.^[2] Dika trees were not cultivated systematically, because it was believed, that it takes up to 15 years until a tree bears fruit. Although they were not planted, their occurrence is high because they were also rarely lumbered. In a plantation using marcots (air-layering plants), flower production was observed two to four years after planting.^[2] Germination from seeds is low and when they are not handled carefully, most fail.^[2] The seeds are mostly extracted by breaking them by hand.^[2]

Breeding

The domestication of dika is in its early stages.^[2] Around 1990, vegetative propagation allowed mass replication and selection. Grafting, budding, air-layering, marcotting and cuttings are feasible when they are applied to young wood.^[2]

Uses

Humans eat the fruits fresh, leading to the misnomer, African mango.^[1] The fruits are processed into jelly, jam, juice and sometimes even wine.^[3] The pulp has also been used to prepare black dye for cloth coloration.

The seed coat has to be cracked open to get to the endosperm. Seeds, also called dika nuts, are eaten raw or roasted. Mostly however they are pounded to butter- or a chocolate-like block.^[4] Seeds can be pressed to produce an edible oil (solid at ambient temperatures) or margarine used for cooking. The oil can also be processed further to soap or cosmetics.^[4] The press cake can be used as cattle feed or as thickening agent for soup. Seeds can be ground or crushed and used as a thickening and flavoring agent in soups and stews.^[1] They can also be made into a cake called "dika bread" for preservation.^[1]

Dika bread

The wood is hard and therefore used for heavy construction work as making ships' decks or railway ties.^[1] Dead branches are used as firewood.^[4]

The trees are used in agroforestry systems to shade other crops, especially cocoa and coffee. They are also used to reduce erosion. Cities have started using them to shade streets, as shelter belts, or for beautification.

Thousands of tons of dika seeds are traded each year, mostly within Africa.

Nutrition

The edible seeds provide 697 calories in a 100 gram portion and the following nutrients:^[4]

The approximate fatty acid composition in seeds includes myristic acid (33–70%), lauric acid (20–59%), oleic acid (1–11%), palmitic acid (2%) and stearic acid (1%).^[4]

Unlike the pulp of some other Irvingia spp., the pulp of Irvingia gabonensis tastes juicy and sweet and is eaten fresh. A 100 gram portion of fruit pulp provides 61 calories and includes:

Fruit pulp flavor components include zingiberene, cinnamic acid, dodecanal and dodecanol, resulting in spicy, earthy, fruity, and wine-yeast characteristics.^[4]

African mango and weight control

Food supplements from dika under the name "African mango" are marketed for management of body weight. Clinical trials to date have not unequivocally confirmed their efficacy, although a meta-analysis concluded that Irvingia gabonensis showed "some potential benefit for weight loss",^[5] stating that "it appears to be safe and well tolerated as the most common adverse effects are headache, flatulence, and difficulty sleeping".^[5]

References

External links

• "Irvingia gabonensis". Forest Products Laboratory Tech Sheet. United States Department of Agriculture. 
• "Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill.". Protabase record display. Prota. 

• Irvingia gabonensis in West African plants – A Photo Guide.