Cordeauxia

Taxonomy

Cordeauxia edulis is a leguminous plant (Fabaceae) from the genus Cordeauxia. The genus Cordeauxia is in subfamily Caesalpinioideae and tribe Caesalpinieae, and is closely related to the genera Caesalpinia and Stuhlmannia. There are at least two varieties of the species C. edulis: Moqley and Suley. Other names are Yebb, Hebb, Ye'eh, Yi-ib, Yehib or Yicib. In amharic it is called Ehb, Qud or Quda.

History

The yeheb nut bush has been known to the Somali nomads for centuries. The first recovery of his existence dates back to 1871, when the Italian esplorer Luigi Robecchi Bricchetti noticed the plant when traversing Somalia to Bari. The bush has been named after Cordeaux, a botanic who first obtained botanical specimens in the Ogaden province (Somali Galbeed) which were found to be a leguminous plant belonging to a hitherto unknown genus in the Caesalpinaceae. Afterward, Hemsley gave the plant the generic name Cordeauxia, with the specific epithet edulis (edible). In 1929, the yeheb bush covered half of the vegetation of large territories in Somalia and Somali region. In 1983 the distribution has been reduced to small regions.

Distribution

The yeheb tree is native in the arid and semi-arid areas in Somalia (Ogaden). found that the species had disappeared from the Haud plateau of Somaliland, although still to be found on the Ethiopian side of the border.

It is exotic in Israel, Kenya, Sudan, Tanzania and in the Republic of Yemen. Today there is germplasm collection in Ethiopia (ILRI Addis Ababa), Kenya (National Genebank, Kikuyu) and the USA (Southern Regional Plant Introduction Station, Griffin, Georgia).

Biology

It is an evergreen, multistemmed shrub of about 1.6m height but it can also grow up to 4 m. The Yeheb tree has a taproot system, which can go 3m deep. Like that it reaches deep water and can stay green all year round.

• Leaves: The lower surface of the leaves is green with glandular hair. The hair contain cordeauxiaquinone, a magenta-red pigment. The leaves measure 3–5 cm. They curl when the soil moisture gets low.
• Flowers: The flowers are yellow and contain both sexes. They are 2–5 cm in diameter and have 5 petals. They are grouped in corymbs with very few flowers at the end of the branch. Flowering occurs throughout the year but is more profuse during the rainy season. They are pollinated by insects. The flowers develop at the first stage of the fruit formation, exhibit a dormancy through the dry season and continue the development at the onset of the next rainy period. After that, they mature within a few days.
• Seeds: They have the size of a big hazel-nut, weight 1–3 g and are red-brown. The indehiscent pods include 1–4 round or ovoid seeds, they are by mistake called nuts. The germination rate is about 80% growth.
• Trunk and Bark: They have a yellow-brownish color.
• Growth: The growth in the first developing stages is slow due to small proportion of reserve proteins and the development of the taproot system.
• Chromosome number: 2n=24
• Inflorescence: The inflorescence is a terminal few-flowered raceme.

Cultivation

C. edulis is cultivated on a small scale in Somalia and near Voi in Kenya. It has only recently been a subject to domestication, therefore little knowledge about propagation, the agronomic practices and its potential for selection as well as breeding exists. The potential of this multipurpose plant is very promising, especially for other arid, hot regions as an important food and fodder resource.

Environmental requirements

C. edulis is a drought resistant plant and tolerant to desertification. For optimal plant development, average temperature and rainfall requirements are 25 °C and 250 - 400mm/year (two rainy seasons). Occasionally the Yeheb tree can also cope with minimal precipitation levels of 150–200 mm/year. It grows on red sandy soils (called Haud) with a low nitrogen content. The soils are alkaline and their texture is fine to coarse sand or grit to loamy sand. C. edulis prefers elevated stands, where no water accumulates. It grows in altitudes between 100–1000 m and is found in vegetation with acacia-commiphora deciduous bushland and thickets.

Sowing

The seed is often said to be viable for a few months only, but seed coated in wood ash and stored in a sack is reputed to remain viable for at least a year. The seeds should be sown on soils where the taproot can develop. There is no information available on optimal density and spacing. Under natural conditions there are up to 320plants/ha. The seedlings need ample water after planting. A transplantation of the plant destroys the taproot and leads to mortality.

Harvest

The yeheb seeds are usually harvested from wild plants. but in Somalia nowadays the harvest is reported to occur twice a year. This is possible if both rainy seasons occur within their normal extent and contribute enough rain for the plant. The Yeheb-Nut is mainly harvested manually by children and women, and the harvest process is described as hard work. Due to the high demand and many droughts in the last few years, the shrub is often harvested immature at an age below 3 years. The plants are often overused as the people remove all seeds at the same time.

Yield

Yeheb produces few fruits in the first three years, but it can live up to many years. The quantity of the yield increases with higher age, but also depends on the amount of rainfall. The yield is about 5–8 kg seeds. The estimated average forage production is 325–450 kg/ha.

Postharvest treatment and storage

The seeds are rarely eaten fresh by Somali children, more often they are first dried in the shade during 7–10 days and then the hard seed coat is removed. For storage, the seeds have to be roasted or boiled to prevent fungal attack, to kill insects eggs and larvae inside the seeds and to harden the seed coat. After roasting in the hot ash, which leads to yield losses due to damage of the seeds, the seeds are coated in weed ash and stored in sacks in the house for personal use or for trade at local markets at a later time. The seeds treated this way are storable for about one year. Pastoralists keep the seeds in containers out of dried and tanned camel leather, where they can be stored for many years. The firewood for roasting is often taken from the shrub, which hampers the regeneration of the population in addition to the complete removal of all the seeds.

Use

The seeds are usually consumed by local people and rarely sold in town. The demand exceeds the supply, because the plant population is declining.

Human Use

• Food: The seeds are eaten dried, boiled, roasted or raw. Sometimes the seeds of C. edulis is the only available food for Somali nomads during droughts. The seeds are nutritious and taste sweet with a chestnut flavour after roasting. Fresh or dried seeds taste sour. Local people like its taste so there is a saying Fadhi iyo Fuud Yicibeed lays la waa", which means: Those who remain seated and laze will not get Yihib. The raw seeds contain a considerable amount of serine protease (trypsin) inhibitors, causing nausea or stomach distress. These inhibitors are destroyed by heating during cooking or roasting.
• Drinks: People made a tea out of the leaves or drink the sweet water in which the seeds have been boiled as a beverage.
• Medicine: C. edulis can regulate gastric secretion. A study showed that the consumption of the plant enhances the production of erythrocytes and is therefore used as a remedy for anemia.

Forage

C. edulis is an important bee forage. but the shrubs cannot withstand long-term grazing pressure. During the rainy season, the animals usually avoid the plant because of its high content of tannins in the leaves (see table below). C. edulis can cause intestinal disorders in goats when eaten as the sole diet.

C. edulis also contains a naphthoquinone, cordeauxione (cordeauxiaquinone). It is found in the glands of the leaves and is unique for C.edulis. It is used as a red dye. If goats browse on the leaves of C. edulis, their feet become light-orange in color and their urine turn purple. As Cordeauxione makes calcium complexes, teeth of animals get orange-red and their bones pink when they eat the leaves. The pink bones are considered a sign of good meat quality in Somalia and Saudi Arabia.

Industrial Use

• Fuel: The wood is a good firewood, also when wet.
• Insect defence: Roasting or boiling of freshly picked seeds provide a good insect defence.
• Industry: The red dye in the glands of the leaves can be used for dyeing textiles. The dye can also be extracted by alkaline or acid dissolver, whereas first leads to a more intense violet color.
• Soap: Soap can be made out of the seed oil.
• Construction timber: The wood is popular as a building material due to its resistance to termites.

Other uses

• Livestock fences
• Nitrogen fixation
• Soil conservation
• Mulch

International trade

There is some trade between Ethiopia, Somalia and Arabia, but no quantitative information available. The Yeheb seed is suggested by many studies to have a potential market in Europe as a "dessert nut".

Pests and diseases

• Seeds: weevils and moth larvae
• Shrubs: rarely any insect pests

Nutritional aspects

The seeds are rich in starch, sugar, protein and fat. The Suley variety shows higher protein and fat content than the Moqley variety. Their carbohydrate and protein contents are less than those of most other legumes eaten in the Horn of Africa. However, C. edulis grows where it is impossible for the usual legumes to grow. The amino-acid composition of C.edulis is close to that of the Papilionaceae (e.g. Methionine-deficient).

The seeds of yeheb are rich in sodium, potassium and phosphorus; thus they contain a small amount of calcium and magnesium.

Both varieties contain a lot of amino acids; yeheb seeds have a high content of the essential amino acids lysine and arginine, but are deficient in tryptophan and isoleucine. Phytohaemagglutinin, a toxic lectin often present in legumes, is absent in Yeheb seeds; this is an additional nutritional advantage.

References

References

1. Beech, E.. (2021). "''Cordeauxia edulis''".
2. The Legume Phylogeny Working Group (LPWG).. (2017). "A new subfamily classification of the Leguminosae based on a taxonomically comprehensive phylogeny". [[Taxon (journal).
3. (2016). "A new generic system for the pantropical ''Caesalpinia'' group (Leguminosae)". PhytoKeys.
4. (2006). "Cereals and pulses". PROTA Foundation.
5. AgroForestryTree Database [https://archive.today/20130416071007/http://www.worldagroforestrycentre.org/sea/products/afdbases/af/asp/SpeciesInfo.asp?SpID=587] 13.10.13
6. Baumer, Michel. (1983). "Notes on trees and shrubs in arid and semi-arid regions". Food and Agriculture Organization of the United Nations.
7. Králová, B.. (1982). "The nutritional value of Yeheb-nut (Cordeauxia edulis Hemsl.)". Food/Nahrung.
8. Jacques. (1978). "Cordeauxia Edulis — A caesalpiniaceae of arid zones of East Africa". Economic Botany.
9. Ismail, Muna. (2015). "Report of a scoping mission to examine the restoration and possible domestication of the Yeheb plant in Somaliland". Initiatives of Change.
10. Booth, F.E.M.. (1988). "Non-timber uses of selected arid zone trees and shrubs in Africa". Food and Agriculture Organization of the United Nations.
11. Mahony, Desmond. (1990). "Trees of Somalia". Oxfam.
12. Yusuf, Mussa. (1 June 2013). "Traditional knowledge and practices on utilisation and marketing of Yeheb (Cordeauxia edulis) in Ethiopia". Agroforestry Systems.
13. Baumer, Michel. (1983). "Notes on trees and shrubs in arid and semi-arid regions". Food and Agriculture Organization of the United Nations.
14. Furthermore, it serves as fodder for camels, goats, sheep and cattle in dry seasonHeuzé V., Thiollet H., Tran G., Lebas F., 2017. Yeheb (Cordeauxia edulis). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/598
15. Ali, Hussein Mohamed. (1988). "Cordeauxia edulis: Production and forage quality in Central Somalia". Somali National University.
16. Birnie, Azene Bekele-Tesemma with Ann. (1993). "Useful trees and shrubs for Ethiopia: identification, propagation, and management for agricultural and pastoral communities". Regional Soil Conservation Unit, Swedish International Development Authority.