Cucurbit Resources in Namibia

Namibia has several cucurbits with potential for development into commercial crops either through selection or through the introduction of genes into known crops. Acanthosicyos horrida Welw. ex J.D. Hook., wild Citrullus ecirrhosus Cogn., and C. lanatus (Thunb.) Matsum. & Nakai in the Cucurbitaceae are examples of gene sources. The areas from which these plants come are arid and the plants derive their water needs from dew precipitation in the mornings, very occasional rains every few years, and deep ground water (Seely l987; Lovegrove 1993).

ACANTHOSICYOS HORRIDA

Acanthosicyos horrida forms clumps of vegetation in the dunes of the Sossuvlei region near Walvis Bay (Fig. 1) (Craven and Marais 1986; Lovegrove 1993; Klopatek and Stock 1994). Acanthosicyos horrida is a dioecious perennial cucurbit attaining a height of about 1.5 m (Fig. 2). It forms plants of one sex in single clumps which may touch plants of the same or other sex nearby (Fig. l). It bears deep water table seeking roots (G. Wardell–Johnson, pers. commun. 1998). The plants are totally leafless (Fig. 2) and have a fruiting habit of oblong spherical fruits reaching up to 25 cm average diameter. The plants are able to build up sand deposits around themselves and continuously grow to be above these sand deposits. New plants establish only when rain falls and quickly form deeply growing roots that seek the water table (G. Wardell–Johnson, pers. commun. 1998).

Fig. 1. View of Acanthosicyos horrida in sand dunes at the Sossuvlei region near Walvis Bay Namibia.	Fig. 2. A close up of Acanthosicyos horrida plants. Note the leaflessness.

The fruit may not be spaced apart and may occur in clusters of several touching each other. The fruits are spiny (Fig. 3). Maturation of the fruits occurs between February and April. The fruits do not change color and remain green on the outside but the flesh surrounding the seeds dissociates from the skin, turns orange in color (Fig. 4), extremely sweet in taste and strongly aromatic. Maturational changes are easily detected by the bushmen living in the area without breaking the fruit in any way. The fruits are used by the bushmen for two main purposes. The first is for the extraction of the seed which are consumed as pips by splitting in the mouth and the second is for pulp processing where the flesh is boiled and poured to form a fruit leather. This fruit leather is eaten throughout the year and is considerably less flavorful than the pulp. The plant thus forms an important food resource because of the easy storage of both the seeds and the dried pulp (leather). The fruits are eaten also when immature by animals including jackals and rodents who do not seem to be bothered by the bitter taste of the fruits caused by cucurbitacins (Hylands and Magd 1986).

Fig. 3. Back of a mature fruit of Acanthosicyos horrida showing the large spines on the surface of the fruit. The distances separating the spines are small in young fruits.	Fig. 4. Cross section through three fruits of Acanthosicyos horrida. The one on the extreme right is a bitter immature fruit of full size. The one on the top an almost mature fruit with only a little bitterness. The bottom left hand fruit a fully mature fruit with a flesh having an orange color, no bitterness and very aromatic in flavor.

The mature pulp has a flavor which is aromatic and maybe due in part to sulphur components as in some types of Cucumis melo L. No trace can be tasted of cucurbitacins in the mature pulp. The pulp could be commercialized and used to make ice-cream, and could be freeze dried and chocolate coated. The seeds which are already sold to an European population in Walvis Bay can have their market expanded by selling the seeds either whole or dehusked in packaging developed for nuts. Their rarity should provide a premium price and help the economic existence of the bushmen in this area. Ice-cream manufacture and freeze drying facilities are only within 30 km of the bushmen. Partnerships with firms interested in commericalizing the unique, aromatic pulp of Acanthosicyos horrida could be fostered to further improve the economic existence of the native people in the area.

CITRULLUS ECIRRHOSUS

Citrullus ecirrhosus is a desert perennial (Fig. 5, 6) which is monoecious. Fruits mature (Fig. 7, 8) February to March. The leaves form an annual stems which die back each year. The leaves have a special feature where the lamina is curved over the mid-rib and the lateral veins so that when viewed from above the top surface is only visible in the vein regions and the leaves have a greenish white appearance due to the lower epidermis being reflected up as the upper surface of the leaf. This lower epidermis is covered with warts and hairs which account for the whitening effect. Both lower and upper epidermis contain similar amounts of stomata. The water relations of this plant are reliant on a deep water layer in the ground which the roots reach and possibly some water availability from morning fogs and the very occasional rainfall. The fruit and seeds contain cucurbitacins but the seeds are harvested in times of need and processed by crushing and decantation to remove the bitter substances. Citrulls ecirrhosus plants may be a source of drought tolerance genes for Citrulls lanatus. Successful crossability of Citrulls ecirrhosus and C. lanatus is discussed in Navot and Zamir (1986) and Navot et al. (1990). They have shown the way for breeding Citrullus lanatus containing genes from C. ecirrhosus.

Fig. 5. Citrullus ecirrhosus perennial plant growing approximately 20 km inland from Walvis Bay, showing a mature fruit on current years growth and brown dead stems from last years growth.	Fig. 6. Citrullus ecirrhosus perennial plant showing young developing fruit in the foreground and the bending of the leaves over the mid-rib and lateral veins.

Fig. 7. Mature Citrullus ecirrhosus showing folded nature of the leaves of the mid-rib and lateral veins.	Fig. 8. Fruit of Citrullus ecirrhosus cut showing white creamy flesh which is non juicy and brown seeds.

Fig. 9. Citrullus lanatus mature fruit from a plant growing on a dry river bed approximately 20 km inland from Walvis Bay, cut to show chlorophyll in the flesh and browny-black seeds. The more deeply colored regions of the flesh are green. The flesh is more juicy than in Citrullus ecirrhosus.

CITRULLUS LANATUS

Citrullus lanatus wild plants seen near Walvis Bay have green fleshed fruit unknown from domesticated watermelons (Fig. 9). The genetics of fruit color in the watermelon, Citrullus colocynthis and ecirrhosus are discussed by Navot et al. (1990). White, yellow, orange, pink, red, and crimson flesh types are known. The green flesh color of this wild Citrullus lanatus (Fig. 9) is a unique feature which can be transferred to domestic watermelon due to the crossability of wild and domestic watermelons. This would offer a new fruit type for consumers to enjoy. A red flesh cultivated watermelon from the north of Namibia has some green zone within the fruit suggesting that the green flesh character can be easily introduced. However, the wild watermelon has cucurbitacins which would render them unfit for human consumption. Drought tolerance and green flesh color from C. ecirrhosus and wild Citrullus lanatus, could be valiable traits for watermelon improvement.

REFERENCES

• Craven, P. and C. Marais. 1986. Namib Flora Swakopmund to the Giant Welwitschia via Goanikontes. Gamsberg MacMillan Publishers: Windhoek. p. 80–83.

• Hylands, P.J and M.S. Magd. 1986. Cucurbitacins from Acanthosicyos horridus. Phytochemistry 25:1681–1684.

• Klopatek J.M. and W.D. Stock. 1994. Partitioning of nutrients in Acanthosicyos horrida, a keystone endemic species in the Namib Desert. J. Arid Environments 26:233–240.

• Lovegrove, B. 1993. The living deserts of Southern Africa. Fernwood Press, Vlaeberg, South Africa. p. 30, 47, 71, 158, 190.

• Navot, N. and D. Zamir. 1987. Isozyme and seed protein phylogeny of the genus Citrullus (Cucurbitaceae). Plant Syst. Evol. 156:61–68.

• Navot, N., M. Sarfatti, and D. Zamir. 1990. Linkage relationships of genes affecting bitterness and flesh colour in watermelon. J. Hered. 81:162–165.

• Seely, M. 1986. The Namib. Shell Namibia: Namibia. 2nd ed. 19, 43–45, 50, 84, 90.

Cucurbit Resources in Namibia

Namibia has several cucurbits with potential for development into commercial crops either through selection or through the introduction of genes into known crops. Acanthosicyos horrida Welw. ex J.D. Hook., wild Citrullus ecirrhosus Cogn., and C. lanatus (Thunb.) Matsum. & Nakai in the Cucurbitaceae are examples of gene sources. The areas from which these plants come are arid and the plants derive their water needs from dew precipitation in the mornings, very occasional rains every few years, and deep ground water (Seely l987; Lovegrove 1993).

ACANTHOSICYOS HORRIDA

Acanthosicyos horrida forms clumps of vegetation in the dunes of the Sossuvlei region near Walvis Bay (Fig. 1) (Craven and Marais 1986; Lovegrove 1993; Klopatek and Stock 1994). Acanthosicyos horrida is a dioecious perennial cucurbit attaining a height of about 1.5 m (Fig. 2). It forms plants of one sex in single clumps which may touch plants of the same or other sex nearby (Fig. l). It bears deep water table seeking roots (G. Wardell–Johnson, pers. commun. 1998). The plants are totally leafless (Fig. 2) and have a fruiting habit of oblong spherical fruits reaching up to 25 cm average diameter. The plants are able to build up sand deposits around themselves and continuously grow to be above these sand deposits. New plants establish only when rain falls and quickly form deeply growing roots that seek the water table (G. Wardell–Johnson, pers. commun. 1998).

Fig. 1. View of Acanthosicyos horrida in sand dunes at the Sossuvlei region near Walvis Bay Namibia.	Fig. 2. A close up of Acanthosicyos horrida plants. Note the leaflessness.

The fruit may not be spaced apart and may occur in clusters of several touching each other. The fruits are spiny (Fig. 3). Maturation of the fruits occurs between February and April. The fruits do not change color and remain green on the outside but the flesh surrounding the seeds dissociates from the skin, turns orange in color (Fig. 4), extremely sweet in taste and strongly aromatic. Maturational changes are easily detected by the bushmen living in the area without breaking the fruit in any way. The fruits are used by the bushmen for two main purposes. The first is for the extraction of the seed which are consumed as pips by splitting in the mouth and the second is for pulp processing where the flesh is boiled and poured to form a fruit leather. This fruit leather is eaten throughout the year and is considerably less flavorful than the pulp. The plant thus forms an important food resource because of the easy storage of both the seeds and the dried pulp (leather). The fruits are eaten also when immature by animals including jackals and rodents who do not seem to be bothered by the bitter taste of the fruits caused by cucurbitacins (Hylands and Magd 1986).

Fig. 3. Back of a mature fruit of Acanthosicyos horrida showing the large spines on the surface of the fruit. The distances separating the spines are small in young fruits.	Fig. 4. Cross section through three fruits of Acanthosicyos horrida. The one on the extreme right is a bitter immature fruit of full size. The one on the top an almost mature fruit with only a little bitterness. The bottom left hand fruit a fully mature fruit with a flesh having an orange color, no bitterness and very aromatic in flavor.

The mature pulp has a flavor which is aromatic and maybe due in part to sulphur components as in some types of Cucumis melo L. No trace can be tasted of cucurbitacins in the mature pulp. The pulp could be commercialized and used to make ice-cream, and could be freeze dried and chocolate coated. The seeds which are already sold to an European population in Walvis Bay can have their market expanded by selling the seeds either whole or dehusked in packaging developed for nuts. Their rarity should provide a premium price and help the economic existence of the bushmen in this area. Ice-cream manufacture and freeze drying facilities are only within 30 km of the bushmen. Partnerships with firms interested in commericalizing the unique, aromatic pulp of Acanthosicyos horrida could be fostered to further improve the economic existence of the native people in the area.

CITRULLUS ECIRRHOSUS

Citrullus ecirrhosus is a desert perennial (Fig. 5, 6) which is monoecious. Fruits mature (Fig. 7, 8) February to March. The leaves form an annual stems which die back each year. The leaves have a special feature where the lamina is curved over the mid-rib and the lateral veins so that when viewed from above the top surface is only visible in the vein regions and the leaves have a greenish white appearance due to the lower epidermis being reflected up as the upper surface of the leaf. This lower epidermis is covered with warts and hairs which account for the whitening effect. Both lower and upper epidermis contain similar amounts of stomata. The water relations of this plant are reliant on a deep water layer in the ground which the roots reach and possibly some water availability from morning fogs and the very occasional rainfall. The fruit and seeds contain cucurbitacins but the seeds are harvested in times of need and processed by crushing and decantation to remove the bitter substances. Citrulls ecirrhosus plants may be a source of drought tolerance genes for Citrulls lanatus. Successful crossability of Citrulls ecirrhosus and C. lanatus is discussed in Navot and Zamir (1986) and Navot et al. (1990). They have shown the way for breeding Citrullus lanatus containing genes from C. ecirrhosus.

Fig. 5. Citrullus ecirrhosus perennial plant growing approximately 20 km inland from Walvis Bay, showing a mature fruit on current years growth and brown dead stems from last years growth.	Fig. 6. Citrullus ecirrhosus perennial plant showing young developing fruit in the foreground and the bending of the leaves over the mid-rib and lateral veins.

Fig. 7. Mature Citrullus ecirrhosus showing folded nature of the leaves of the mid-rib and lateral veins.	Fig. 8. Fruit of Citrullus ecirrhosus cut showing white creamy flesh which is non juicy and brown seeds.

Fig. 9. Citrullus lanatus mature fruit from a plant growing on a dry river bed approximately 20 km inland from Walvis Bay, cut to show chlorophyll in the flesh and browny-black seeds. The more deeply colored regions of the flesh are green. The flesh is more juicy than in Citrullus ecirrhosus.

CITRULLUS LANATUS

Citrullus lanatus wild plants seen near Walvis Bay have green fleshed fruit unknown from domesticated watermelons (Fig. 9). The genetics of fruit color in the watermelon, Citrullus colocynthis and ecirrhosus are discussed by Navot et al. (1990). White, yellow, orange, pink, red, and crimson flesh types are known. The green flesh color of this wild Citrullus lanatus (Fig. 9) is a unique feature which can be transferred to domestic watermelon due to the crossability of wild and domestic watermelons. This would offer a new fruit type for consumers to enjoy. A red flesh cultivated watermelon from the north of Namibia has some green zone within the fruit suggesting that the green flesh character can be easily introduced. However, the wild watermelon has cucurbitacins which would render them unfit for human consumption. Drought tolerance and green flesh color from C. ecirrhosus and wild Citrullus lanatus, could be valiable traits for watermelon improvement.

REFERENCES

• Craven, P. and C. Marais. 1986. Namib Flora Swakopmund to the Giant Welwitschia via Goanikontes. Gamsberg MacMillan Publishers: Windhoek. p. 80–83.

• Hylands, P.J and M.S. Magd. 1986. Cucurbitacins from Acanthosicyos horridus. Phytochemistry 25:1681–1684.

• Klopatek J.M. and W.D. Stock. 1994. Partitioning of nutrients in Acanthosicyos horrida, a keystone endemic species in the Namib Desert. J. Arid Environments 26:233–240.

• Lovegrove, B. 1993. The living deserts of Southern Africa. Fernwood Press, Vlaeberg, South Africa. p. 30, 47, 71, 158, 190.

• Navot, N. and D. Zamir. 1987. Isozyme and seed protein phylogeny of the genus Citrullus (Cucurbitaceae). Plant Syst. Evol. 156:61–68.

• Navot, N., M. Sarfatti, and D. Zamir. 1990. Linkage relationships of genes affecting bitterness and flesh colour in watermelon. J. Hered. 81:162–165.

• Seely, M. 1986. The Namib. Shell Namibia: Namibia. 2nd ed. 19, 43–45, 50, 84, 90.

Acacia tortilis (Forsk.) Hayne

Syn.: Acacia raddiana Savi,
Acacia spirocarpa Hochst. ex A. Rich
Acacia heteracantha Burch.
Mimosaceae
Umbrella Thorn, Israeli Babool

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Since this is one of the few timber species of the Arabian deserts, it is suspected as being the wood from which the Biblical Ark of the Tabernacle was made. Kaplan (1979) says rather emphatically it is the Shittim of the Bible, which provided the Israelites with the large-size timbers for the Ark. The timber is also used for fenceposts, firewood, furniture, and wagonwheels. The prolific pods made good fodder for desert grazers and the foliage is also palatable, being one of the major dry season fodder trees for the Sahara-Sahelian belt. Bark, used for string in Tanganyika. Gum used as a poor man's gum arabic, said to be edible. It is the tree most recommended for reclaiming dunes in India and Africa (Roy et al, 1973). The thorny branches are used to erect temporary cages and pens. Bark said to be a good source of tannin (Roy et al, 1973). Africans once strung the pods into necklaces. Senegalese use the roots for spear shafts, Lake Chad natives use the stems for fish spears. African nomads often use the flexible roots for frameworks of their temporary shelters.

Folk Medicine

While I find few data specific to this species, I suspect that the gum is used like that of gum arabics in folk remedies. In French Guinea, the bark is used as a vermifuge and dusted onto skin ailments (Dalziel, 1937).

Chemistry

Pods contain close to 19% protein (Palmer and Pitman, 1972). NAS (1979) reports unconfirmed allegations that the foliage can be toxic to livestock. Certainly HCN has been reported in several Acacias. The following tables are reproduced, with permission, from FAO's Tropical Feeds (1981):

Nutritive tables (Gohl, 1981)

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, South Africa		19.2	11.6	8.7	6.1	54.4	2.27	0.17	213
Pods, South Africa		17.3	24.8	5.7	3.1	49.1	0.79	0.34	213
Seeds, South Africa		37.8	10.9	5.9	6.0	39.7	0.56	0.73	213
Pod husks, South Africa		8.7	34.3	6.2	1.6	49.2	1.10	0.14	213

Acacia tortilis (Forsk.) Hayne subsp. heteracantha (Burch.) Brenan

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, Sudan	90.9	13.3	9.4	9.6	8.3	59.4	4.00	0.15	64
Pods, Tanzania		12.3	22.4	5.6	1.8	57.9	0.98	0.24	166
Pods, Kenya		17.8	17.5	8.4	1.7	54.6	1.34	0.36	129

		Digestibility (%)
	Animal	CP	CF	EE	NFE	ME	Ref
Pods	Cattle	46.2	42.0	74.0	76.6	2.30	166

Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan

Description

Medium umbrella-shaped tree 4–15 m tall, often with several trunks, reduced to a small wiry shrub less than 1 m tall under extremely arid conditions. Two types of thorns abound (1) long, straight, and white, and (2) small, hooked, and brownish. Leaves up to 2.5 cm long with 4–10 pairs of pinnae, each with ca 15 pairs of minute leaflets. Flowers white, aromatic, in small clusters. Pods flat, glabrose, coiled into a spring-like array.

Germplasm

Reported from North African and Middle Eastern Centers of Diversity, Umbrella Thorn, or cvs thereof, is reported to tolerate alkalinity, drought, heat, sand, slope, and stony soils. It seems to be more frost tolerant than Prosopis juliflora, still plants less than 2 years old are easily damaged by frost. Four subspecies are known in different ecological zones: subspecies tortilis—Sahel, Middle East; subspecies raddiana—Sudan, Middle East, Sahel(2n=104); subspecies spirocarpa—Eastern Africa, Sudan; and subspecies heteracantha—Southern Africa (2n= 52). The different subspecies seem to have different ecological tolerances, which is important to consider when choosing a subspecies for plantations. (2n= 52, 104)

Distribution

Native to much of Africa and the Middle East, this species has been introduced in many arid parts of the world. Ironically, it grows faster in the Rajastan Desert of India, where used for charcoal, firewood, and fodder, than in its native Israel (Kaplan, 1979). In Malawi, this species is already scorned by the rural public because it is thorny and difficult to work with. It is being tried for fencings (Nkaonja, 1980).

Ecology

Deemed the most promising of 56 Acacia species tried at Jodhpur, India. Probably ranging from Subtropical Desert to Dry through Tropical Desert Scrub to Very Dry Forest Life Zones, umbrella tree is reported to tolerate annual precipitation of 1 to 10 dm, estimated annual temperature of 18 to 28°C, and pH of 6.5 to 8.5. This species tolerates hot, arid climates with temperatures as high as 50°C subspecies raddiana grows where minimum temperatures are close to 0°C. It is best adapted to the lowlands. It thrives where rainfall is up to 1,000 mm. However, it is also extremely drought resistant and can survive in climates with less than 100 mm annual rainfall with long, erratic dry seasons. The tree favors alkaline soils. It grows fairly well in shallow soil, less than 0.25 m deep, though it develops long lateral roots that can become a nuisance in nearby fields, paths, and roadways. In shallow soil, the plants remain shrubby and must be widely spaced to allow for their lateral root growth.

Cultivation

For good seed germination, seeds should be treated with concentrated sulphuric acid for 30 minutes (Roy et al, 1973). Artificial regeneration aiming at large-scale nursery production requires full use of the germination capacity of the available seeds. This may be achieved by sulfuric acid pretreatment, which brings about the germination of all viable seeds. Treatment with boiling water is selective and mainly breaks the dormancy of bruchid-infested seeds, some of which are no longer able to germinate. Sowing of unripe seeds without pretreatment may be called for as an emergency measure in case of very severe infestation, to achieve at least partial success. Prior to storage, seeds should be fumigated to arrest progressing deterioration of seed viability by bruchids (Karschon, 1975). NAS (1980a) recommends dipping the seed in hot water to soak overnight. Seedlings require initial weeding to facilitate faster growth. Plantations can be spaced at 3 x 3 m.

Harvesting

Firewood harvested as needed, but 10-year rotations are suggested. In Jodhupr, flower initiation is ca May-June in 3-year old trees, fruits forming in July but ripening from November through February. Since the tree coppices well, there is no need to replant after every harvest.

Yields and Economics

Eleven-year old trees in deep sandy soils at Jodhpur averaged 6.4 m tall and 14 cm DBH. In shallow sandy loams over hardpan at Pali, India, 7-year old trees (98% survival) averaged 4.8 m tall, and 10 cm DBH. In sanddunes at Barmer, India, 5-year old trees averaged 3 m tall, 7 cm DBH. An average tree yields 6 kg pods of which 2.6 kg is clean seed. One tree is said to yield 14–18 kg pods and leaves per year in India (Muthana and Arora, 1980). Acacia tortilis has been reported to yield giraffe forage at 5 MT/ha/yr.

Energy

A 12-year-old plantation in India yielded 54 MT fuel , suggest, annual returns of 4.5 MT, not a bad return for the desert (NAS, 1980a). The heartwood has calorific value of 4,400 kcals/kg, making superior firewood and charcoal. It is one of the main firewood and charcoal sources in parts of Africa, e.g. around Khartoum. Nitrogen-fixing nodules are reported in South Africa and Zimbabwe.

Biotic Factors

Bruchids often damage or destroy the seeds, on the tree or after collecting. Herbivores, tame and wild alike, are liable to graze seedlings and innovations. Trees attacked by beetles, mimosoid blights, and caterpillars. The wood is susceptible to termites. In Tanzania, elephants which eat the bark are wiping out some park populations. In Israel, the native Acacias host several species (>40) of mostly monophagous insects, whereas on one exotic, Australian Acacia saligna, only a few polyphagous species occur (Halperin, 1980). Only Microcerotermes diversus and Kalotermes flavicollis, which feed on woody parts of both Acacias and Apate monachus (a beetle which tunnels the stems and branches, causing them to collapse in windblow), may seriously damage the tree. In nature, regeneration and spread of Acacias are probably limited by bruchids destroying much of the seed crop. Seedlings from natural regeneration may come from damaged seeds with a still intact embryo axis, since seedcoat dormancy is removed by the effect of exit holes permitting rapid water absorption and germination. Intact seeds with hard impermeable seedcoats may require a long time to germinate, and probably function as a reserve to ensure the survival of the species (Karschon, 1975).

References

• Dalziel, J.M. 1937. The useful plants of west tropical Africa. The Whitefriars Press, Ltd., London and Tonbridge.
  
• Gohl, B. 1981. Tropical feeds. Feed information summaries and nutritive values. FAO Animal Production and Health Series 12. FAO, Rome.
  
• Halperin, J. 1980. Forest insects and protection in the arid zones of Israel. J. Israel For. Assoc. 30(3/4):68–72.
  
• Kaplan, J. 1979. Some examples of successful use of Acacia for afforestation. J. Israel For. Assoc. 29(3/4):63–64.
  
• Karschon, R. 1975. Seed germination of Acacia raddiana Savi and A. tortilis Rayne as related to infestation by bruchids. Ag. Res. Org. Leaflet 52. Bet Dagan.
  
• Muthana, K.D. and Arora, G.D. 1980. Performance of Acacia tortilis (Forsk) under different habitats of the Indian arid zone. Ann. Arid Zone 19(1/2):110–118.
  
• N.A.S. 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, DC.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Nkaonja, R.S.W. 1980. Dryland afforestation problems in Malawi. J. Israel For. Assoc. 30(3/4):100–105.
  
• Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. 3 vols. A.A. Balkemia, Cape Town.
  
• Roy, A.D., Kaul, R.N., and Gyanchand. 1973. Israeli babool a promising tree for arid and semiarid lands.

Acacia seyal Del.

Uses

According to some Biblical scholars, the Shittah tree is mentioned in the Bible only once (I will plant in the wilderness... the Shittah tree. Isaiah 41), but its wood is referred to many times as shittium, which is the plural of shittah in Hebrew. Some even speculate that it was only natural that Moses should turn to shittium when he came to build the Ark of the Covenant and the Tabernacle and needed beams and timber. No one can really be sure which species of Acacia was meant. Wood is white to yellow-brown, finely-striated with dark lines, coarse-grained, soft, easy to work, polishes well, but discolors eastly with mold and is susceptible to insect attack. Ancient Egyptians made coffins, some still intact, from the wood. Nigerians used sapling stems, or also the roots for spear shafts. Tree also yields a gum of good quality, inferior to that of A. senegal. Systematic tapping has produced a product of better color and taste. Bark contains tannin and yields a red liquid extract. The gum is said to be edible. The leaves are important for forage and the wood for fuel where the trees are abundant. In parts of Africa the tree is important for livestock, natives driving their animals to where it is common and lopping off branches for them, both leaves and young pods being eaten. The pods are sold, especially for fattening sheep. The tree is believed to provide the best firewood in Chad, and the best fodder in Sahelian savannas (NAS, 1980a; Duke, 1983a).

Folk Medicine

The gum is believed to be aphrodisiac. The bark decoction Is used for dysentery and leprosy. Tanganyikans use the bark as a stimulant in tropical Africa. The gum is used as emollient and astringent for colds, diarrhea, hemorrhage and ophhthalmia. Mixed with Acacia sieberana DC, it is used for intestinal ailments on the Ivory Coast. Wood used as a fumigant for rheumatic pains, and to protect puerperal mothers from colds and fevers. Eating the gum is supposed to afford some protection against bronchitis and rheumatism (Duke, 1983a).

Chemistry

This species has been reported to contain 18–20% tannin.

Description

Tree 3–12 m tall, crown flat-topped; bark powdery, white to greenish-yellow or orange-red; sparsely branched, the branches horizontal or ascending; young branchlets with sparse hairs or almost glabrous, with numerous reddish sessile glands; epidermis of twigs becoming reddish and shed annually; leaves often with a large gland on petiole and between the top 1–2 pairs of pinnae; stipules spinescent, up to 8 cm long, ant-galls present or absent; pinnae usually 3–7 pairs, the leaflets in 11–20 pairs, 3–8 cm long, 0.75–1 mm wide, sparingly ciliolate or glabrous; lateral veins invisible beneath; flowers bright yellow, in axillary, pedunculate heads 10–13 mm across, borne on terminal or short lateral shoots of current season; involucel in lower half of peduncle 2–4 mm long; apex of bracteoles rounded to elliptic, sometimes pointed; calyx 2–2.5 mm long, puberulous in upper part; corolla 3.5–4 mm long, glabrous outside; pods 7–20 cm long, 0.5–0.9 cm in diameter, dehiscent, falcate, constricted between seeds, glabrous except for sessile glands, 6–9-seeded; seeds elliptic, 7–9 mm long, 4.5–5 mm wide, compressed, minutely wrinkled, olive-brown to olive; areole 5–6 mm long, 2.5–3.5 mm wide.

Germplasm

Species has several botanical varieties. The two main ones are: A. seyal var. fistula (Schweinf.) Oliv. (A. fistula Schweinf.), is white-barked with some pairs of spines fused at base into 'ant-galls', 0.8–3 cm in diameter, grayish or whitish, often marked with sienna-red and with longitudinal furrows down center, more or less 2-lobed. Found in Zambia, Malawi, and Mozambique. A. seyal var. multijuga Schweinf. ex Baker f. (A. stenocarpa Oliv., pro partem), a shrub or tree, usually less than 5 m tall, sometimes up to 13 m, flattened crown; bark on main stem greenish-brown, peeling in papery rolls; bark on branchlets red-brown, thorns straight, weak, usually less than 2.5 cm long, sometimes absent; pinnae 4–12 pairs, leaflets 10–20 pairs; flowers golden-yellow; pod narrow-linear, strongly curved, up to 10 cm long, 0.6 cm wide, dehiscing on tree. Common in overgrazed pastures and widely distributed in East Africa. Hybrids, A. seyal var. fistula X A. xanthophloea Benth., are known from woodlands on black clay loams on flood plains in Malawi. Pods are conspicuously irregular, 4–11 cm long, 6–10 mm wide, ill-formed and curved. Assigned to the Africa Center of Diversity, shittim wood or cultivars thereof is reported to exhibit tolerance to high pH, heavy soil, insects, mycobacteria, poor soil, salt, savanna, slope, and waterlogging. (2n= 26.)

Distribution

Native to the Sahelian Zone from Senegal to Sudan, it also occurs in Egypt and eastern and southern Africa, from Somalia to Mozambique and Namibia (NAS, 1980a).

Ecology

Trees thrive in Sclerocarya caffra woodlands, wooded grasslands and especially on seasonally flooded black-cotton soils along water courses. Requires a heavy clay-alluvium, but will grow on stony ground at base of hills. Grows at 20–2,100 m altitude. A gregarious savanna tree, ranging from Subtropical Desert to Dry through Tropical Desert to Very Dry Forest Life Zones, shittim wood is reported to tolerate annual precipitation of 8.7–22.8 dm (mean of 7 cases = 15.0 dm), annual mean temperature of 18.7–27.8°C (mean of 7 cases = 24.0°C) and pH of 5.0–8.0 (mean of 5 cases = 6.9).

Cultivation

Propagated from scarified seed. large cuttings are said to strike root readity in moist soils.

Harvesting

Pods, bark or wood are harvested in season from trees or shrubs in native habitats. Gum also obtained from native plantings, in manner similar to that for other gum arabic plants.

Yields and Economics

Gum and other products of some local importance in East Africa, but do not enter international trade.

Energy

The dense wood is highly prized for firewood, in areas where few other plants survive. Considered one of the best firewoods in Chad, it is used in the Sudan to make fragrant fires over which women perfume themselves.

Biotic Factors

Following fungi reported on this plant: Fomes rimosus, Ganoderma lucidum, Leveillula taurica, Ravenelia volkensii, Trametes meyenii, and Uromyces schweinfurthii. Although the plant is reportedly resistant to insect attacks, felled logs may be severely damaged by wood borers.

References

• Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

Acacia seyal Del.

Uses

According to some Biblical scholars, the Shittah tree is mentioned in the Bible only once (I will plant in the wilderness... the Shittah tree. Isaiah 41), but its wood is referred to many times as shittium, which is the plural of shittah in Hebrew. Some even speculate that it was only natural that Moses should turn to shittium when he came to build the Ark of the Covenant and the Tabernacle and needed beams and timber. No one can really be sure which species of Acacia was meant. Wood is white to yellow-brown, finely-striated with dark lines, coarse-grained, soft, easy to work, polishes well, but discolors eastly with mold and is susceptible to insect attack. Ancient Egyptians made coffins, some still intact, from the wood. Nigerians used sapling stems, or also the roots for spear shafts. Tree also yields a gum of good quality, inferior to that of A. senegal. Systematic tapping has produced a product of better color and taste. Bark contains tannin and yields a red liquid extract. The gum is said to be edible. The leaves are important for forage and the wood for fuel where the trees are abundant. In parts of Africa the tree is important for livestock, natives driving their animals to where it is common and lopping off branches for them, both leaves and young pods being eaten. The pods are sold, especially for fattening sheep. The tree is believed to provide the best firewood in Chad, and the best fodder in Sahelian savannas (NAS, 1980a; Duke, 1983a).

Folk Medicine

The gum is believed to be aphrodisiac. The bark decoction Is used for dysentery and leprosy. Tanganyikans use the bark as a stimulant in tropical Africa. The gum is used as emollient and astringent for colds, diarrhea, hemorrhage and ophhthalmia. Mixed with Acacia sieberana DC, it is used for intestinal ailments on the Ivory Coast. Wood used as a fumigant for rheumatic pains, and to protect puerperal mothers from colds and fevers. Eating the gum is supposed to afford some protection against bronchitis and rheumatism (Duke, 1983a).

Chemistry

This species has been reported to contain 18–20% tannin.

Description

Tree 3–12 m tall, crown flat-topped; bark powdery, white to greenish-yellow or orange-red; sparsely branched, the branches horizontal or ascending; young branchlets with sparse hairs or almost glabrous, with numerous reddish sessile glands; epidermis of twigs becoming reddish and shed annually; leaves often with a large gland on petiole and between the top 1–2 pairs of pinnae; stipules spinescent, up to 8 cm long, ant-galls present or absent; pinnae usually 3–7 pairs, the leaflets in 11–20 pairs, 3–8 cm long, 0.75–1 mm wide, sparingly ciliolate or glabrous; lateral veins invisible beneath; flowers bright yellow, in axillary, pedunculate heads 10–13 mm across, borne on terminal or short lateral shoots of current season; involucel in lower half of peduncle 2–4 mm long; apex of bracteoles rounded to elliptic, sometimes pointed; calyx 2–2.5 mm long, puberulous in upper part; corolla 3.5–4 mm long, glabrous outside; pods 7–20 cm long, 0.5–0.9 cm in diameter, dehiscent, falcate, constricted between seeds, glabrous except for sessile glands, 6–9-seeded; seeds elliptic, 7–9 mm long, 4.5–5 mm wide, compressed, minutely wrinkled, olive-brown to olive; areole 5–6 mm long, 2.5–3.5 mm wide.

Germplasm

Species has several botanical varieties. The two main ones are: A. seyal var. fistula (Schweinf.) Oliv. (A. fistula Schweinf.), is white-barked with some pairs of spines fused at base into 'ant-galls', 0.8–3 cm in diameter, grayish or whitish, often marked with sienna-red and with longitudinal furrows down center, more or less 2-lobed. Found in Zambia, Malawi, and Mozambique. A. seyal var. multijuga Schweinf. ex Baker f. (A. stenocarpa Oliv., pro partem), a shrub or tree, usually less than 5 m tall, sometimes up to 13 m, flattened crown; bark on main stem greenish-brown, peeling in papery rolls; bark on branchlets red-brown, thorns straight, weak, usually less than 2.5 cm long, sometimes absent; pinnae 4–12 pairs, leaflets 10–20 pairs; flowers golden-yellow; pod narrow-linear, strongly curved, up to 10 cm long, 0.6 cm wide, dehiscing on tree. Common in overgrazed pastures and widely distributed in East Africa. Hybrids, A. seyal var. fistula X A. xanthophloea Benth., are known from woodlands on black clay loams on flood plains in Malawi. Pods are conspicuously irregular, 4–11 cm long, 6–10 mm wide, ill-formed and curved. Assigned to the Africa Center of Diversity, shittim wood or cultivars thereof is reported to exhibit tolerance to high pH, heavy soil, insects, mycobacteria, poor soil, salt, savanna, slope, and waterlogging. (2n= 26.)

Distribution

Native to the Sahelian Zone from Senegal to Sudan, it also occurs in Egypt and eastern and southern Africa, from Somalia to Mozambique and Namibia (NAS, 1980a).

Ecology

Trees thrive in Sclerocarya caffra woodlands, wooded grasslands and especially on seasonally flooded black-cotton soils along water courses. Requires a heavy clay-alluvium, but will grow on stony ground at base of hills. Grows at 20–2,100 m altitude. A gregarious savanna tree, ranging from Subtropical Desert to Dry through Tropical Desert to Very Dry Forest Life Zones, shittim wood is reported to tolerate annual precipitation of 8.7–22.8 dm (mean of 7 cases = 15.0 dm), annual mean temperature of 18.7–27.8°C (mean of 7 cases = 24.0°C) and pH of 5.0–8.0 (mean of 5 cases = 6.9).

Cultivation

Propagated from scarified seed. large cuttings are said to strike root readity in moist soils.

Harvesting

Pods, bark or wood are harvested in season from trees or shrubs in native habitats. Gum also obtained from native plantings, in manner similar to that for other gum arabic plants.

Yields and Economics

Gum and other products of some local importance in East Africa, but do not enter international trade.

Energy

The dense wood is highly prized for firewood, in areas where few other plants survive. Considered one of the best firewoods in Chad, it is used in the Sudan to make fragrant fires over which women perfume themselves.

Biotic Factors

Following fungi reported on this plant: Fomes rimosus, Ganoderma lucidum, Leveillula taurica, Ravenelia volkensii, Trametes meyenii, and Uromyces schweinfurthii. Although the plant is reportedly resistant to insect attacks, felled logs may be severely damaged by wood borers.

References

• Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.