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Lost Crops of Africa: Fruits, Volume III
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Lost Crops of Africa: Fruits, Volume III 3 BUTTERFRUIT (Safou, Bush Mango) The colorful prunelike morsels of the butterfruit1 (Dacryodes edulis) are well known in Central and West Africa. They are roasted or boiled with maize as a main course, they are enjoyed (fresh or cooked) as snacks, and they feature in traditional ceremonies and special functions. These are commercial fruits that pour into cities and rural markets in considerable quantities. They are especially important in the hot and humid zone stretching from Eastern Nigeria to Angola. There, women peddling the fruits at locations along the highways are a common sight. The trees are much appreciated in their own right. They are deliberately planted in and around countless farm plots as well thousands of villages. Indeed, they occur in most or possibly all West and Central African villages. And from the appearance of both the fruits and the trees it is clear that generations of Africans have exercised selection for quality and desirable growth forms. Many of these trees receive at least rudimentary horticultural care. Indeed, good specimens are zealously protected. And when forests are felled and burned to open up farmland, butterfruits are left standing. As a result of all this interest, the species is a major component of the traditional farming systems in parts of West Africa, especially Nigeria (Eastern, Delta and Edo states), as well as in the four Central African neighbors, Cameroon, Congo-Brazzaville, Congo-Kinshasa, and Gabon. Throughout this region, it is an important source of nutrition and income for many farmers and is among the most widely used fruit trees. Yet for all its geographical spread, ancient heritage, and current value, butterfruit is barely known to science. This is both strange and sad. People tend to like this fruit once they get to know it. Given a push, it could definitely be a bigger contributor, perhaps eventually reaching millions who today have never heard of it. That would contribute to enhancing the welfare 1 In popular literature this fruit is often called “African pear” or “bush mango,” awkward terms that are botanically and culinarily misleading. A common English name in Central Africa is just “plum,” “bush plum,” or “African plum,” due to its shape and color. It is called safou in Angola, Gabon, Cameroon, and the Congos. It is also known in French as “prunier” and the fruits called “prunes.” Because they resemble avocado in composition and texture we suggest “africado” for international marketing purposes.
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Lost Crops of Africa: Fruits, Volume III Butterfruit has not been cultivated to any extent but small organized plantings have already been established in Cameroon. It is, of course, a major component of traditional agroforestry systems, where it is neither scattered nor sporadic. (© Erick C.M. Fernandes, firstname.lastname@example.org) of farmers in some of the most difficult climates for growing food and cash crops. And it could also enhance survival. In southeastern Nigeria, for example, it is traditionally used to get through the hungry season.2 On nutritional grounds alone, the more extensive use of butterfruits could 2 Information from J.C. Okafor.
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Lost Crops of Africa: Fruits, Volume III be a very good thing. The pulp packs a combination of high protein and high energy that makes it a promising weapon for fighting the world’s worst humanitarian problem, protein-calorie malnutrition. Although presently unemployed or even untested in nutrition programs, it could in principle prove a lifesaver for children, nursing mothers, and the desperately sick. In this regard, the essential amino acid concentrations are noteworthy. The levels of lysine, leucine, and threonine are similar to those found in top-quality animal proteins—eggs, milk, and meat, for example—and much higher than those in most plant staple foods such as wheat, barley, rye, rice, maize, sorghum, or melon seed. The oil making up one-third to two-thirds of the pulp is also noteworthy. It is a good source of essential fat for human nutrition, being composed mainly of unsaturated fatty acids. Also, it has good potential for such things as salad dressings and cooking oil. And beyond protein and oil, this fruit provides a good array of minerals, including phosphorus, potassium, calcium, and magnesium. Sodium, on the other hand, is remarkably low (1.5-5.2 mg per 100 g in recent analyses). Despite its nutritional qualities, the fresh fruit does not appeal to everyone. A dessert delight this is not. Although Central and West Africans may consider it delicious, this fruit turns off sugarcoated taste buds. Indeed, many visitors cannot stand its sourness and slipperiness. One needs to develop a taste for even the sweetest types.3 This is not as big a limitation as it may seem. This fruit is used mainly as a vegetable, like tomato, and is generally consumed along with maize, cassava, or plantain. Despite any culinary limitation initial impressions might present, the fruits have enough advantages to warrant much greater development. For one thing, they have a pleasant smell. For another, they are extremely attractive in appearance. Unripe butterfruits are orange, red, pink, or even purple; ripe ones are deep blue, green, violet, or black. On the inside they are just as colorful: the pulp comes in pink, white, green, or pale yellow. The green form is the sweetest; the pink is the prettiest, although most people consider it barely edible. Although we have chosen to place this plant in the volume on fruits, it could equally well be considered an oilseed. Both pulp and seeds contain outstanding amounts of a vegetable oil useful for such things as cooking and cosmetics. Although this oil is not now produced in any quantity, that could change. The plant comes from the same region as the African oilpalm, which a century ago arose from Central-African obscurity to become one of the world’s major crops. According to one estimate, even the nondescript 3 One of our contributors wrote: “It has a resinous taste, which one has got to get used to. But then you become an addict!”
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Lost Crops of Africa: Fruits, Volume III These butterfruit are not just transplanted wild types—they differ greatly from wild fruit in the vicinity, which indicates a high degree of selection by farmers. (© Erick C.M. Fernandes, email@example.com) butterfruit specimens taken straight from the wild can produce more than twice as much oil as their counterparts in the wild oilpalm.4 Whereas the tree is grown in myriad farm fields and village compounds, it is not now cultivated in organized plantations. A few pioneering researchers, however, have established experimental plantings in both Nigeria and Congo, and have achieved results that point the way toward larger scale production.5 Also, oil extraction has advanced to the commercial stage in Gabon and is being tested in Nigeria and Cameroon. And in Congo-Brazzaville, oil processing is being carried out on a pilot scale (100 kg per hour, using an electric oil press).6 Beyond commercial production in orchard-like plantings, the tree is an excellent candidate for household plantings. It has particular promise around 4 Giacomo, R. 1982. Biologie florale du safoutier (Dacryodes edulis) au Gabon. Rapport du projet FAO/CIAM, Libreville, Gabon. Some scientists contend that the butterfruit should have been chosen from the start. It can yield 7-8 tons per hectare, compared with 3 tons per hectare for the wild oilpalm. What it can do in plantations, given some research, is unknown but could be outstanding. 5 Information from J.C. Okafor. The Congo plants are at the University of Kinshasa. 6 Riedaker A. and T. Silou. 1998. Safou. Pp. 227-229 in N. El Bassam, ed., Energy Plant Species. James & James Publishers, London.
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Lost Crops of Africa: Fruits, Volume III the farm and home because it provides so many useful products—including fruits, browse, wood, and a scented resin that burns with a bright flame. Indeed, it is seen as a reliable friend for both times of need and times of plenty. People like having it nearby. This versatile species also has promise for agroforestry and utility use. Even now, it is often seen growing scattered in riverbeds, across hillsides, and along the verges of boulevards. It even has potential in plantation forestry. The timber, although small in diameter and short in length, can substitute for mahogany. Its woodworking qualities and interesting appearance suit it to veneers and fine cabinetwork. Although it has received little formal scientific support, some enthusiasts have rallied to this species. These “crop champions”—who include researchers, extension workers, growers, and traders—joined hands to form a formal bilingual network, the African Safou Network, in the late 1990s.7 Other groups have also shown interest, and butterfruit is slowly finding a more prominent place in research and development in West and Central Africa. Three international organizations have also championed the crop. In southeast and southwest Nigeria, the IFAD-ICRAF-IITA Agroforestry project is selecting varieties which better meet the demands of the growing local market. It is also developing propagation and horticultural techniques. Already, the results have caught the attention of farmers, who have long been frustrated by the trees’ slow maturity. Butterfruit’s potential for greater production and more income appeals to many farmers.8 PROSPECTS Butterfruit could possibly become an African counterpart of the avocado, a protein- and oil-rich fruit that has gone global only within the past 50 years. Avocado is from the American tropics, but is now a substantial resource in a score of countries, including some within Africa itself. Butterfruits are quite unlike avocado in size, shape, or color, but they are very like avocado in their soft, buttery pulp, and in their rich protein and high oil content. Within Africa Considering the place this fruit occupies in its native region, there seems every reason to expect that its improved cultivation will be profitable and rewarding there. It also has promise in many parts of Africa that are now unaware of it. 7 Information from J. Kengue. 8 A forward-looking monograph on butterfruit’s potential is available in French from the International Centre for Underutilised Crops: Kengue, J. 2002. Safou (Dacryodes edulis). Fruits for the Future 3. ICUC, Southampton, UK; see www.icuc-iwmi.org.
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Lost Crops of Africa: Fruits, Volume III Humid Areas Prospects here are high. In much of West and Central Africa’s humid-tropical zones, the butterfruit is already well known and the trees are both deliberately planted and protected from destruction when clearing forest. But its true potential as a major commercial crop is not yet tapped. The species is poised for a breakout, but needs the push of better knowledge to get it to the take-off point. Dry Areas Moderate prospects. The tree withstands extensive dry spells but seems unsuited to truly arid locations. Upland Areas Uncertain prospects. Although no one knows how butterfruit will perform at elevation, the prospects could be substantial, except of course in those locations where frosts are fierce or frequent. Beyond Africa Although so far untried outside Africa, butterfruit is probably not limited to its native continent. Indeed, it seems extremely adaptable and tolerates many combinations of temperature, rainfall, and soils. Taken all round, the species’ prospects for both reforestation and nutrition programs seem to be excellent throughout much of the tropics. USES This is another of the versatile crops producing multiple products of importance to rural peoples, including the following: Fresh Fruits The fruits can be eaten raw, but the pulp softens and comes off the seed easiest after a brief heating. For this reason, most fruits are blanched in hot (sometimes salted) water for a few seconds. At times they are softened by a few minutes roasting in the embers of a fire. Some are fried. A newly developed technique is to pack the fruit in a sealed plastic container and stash it in the sun for an hour. This not only softens the pulp and separates the seed, it saves the fuel. Peel and pulp are normally eaten together, scraped from the seed with the teeth as if eating a mango. Cooked Fruits In some places butterfruits are mostly eaten between meals. More often, the pulp is used to supplement starchy diets based on staples such as maize, cassava, cocoyam, plantain, or sweet potato. In eastern Nigeria the fruits ripen at the same time as maize, and the two are commonly eaten together, usually in the form of snacks.9 In this case the fruits, as well as the maize, are roasted over the embers of a dying fire. In the 9 “This is a very delicious combination,” wrote one of our contributors in Nigeria. “It sells fast and is expensive.”
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Lost Crops of Africa: Fruits, Volume III home this is a minor limitation because it must be cooked after the main part of the meal. For street vendors the problem is more acute because they must keep the fire going, which adds expense. Animal Feed The species has utility as an animal feed. The leaves are fed to livestock to good effect. The kernel found inside the stone at the center of the fruit contains over 3 percent protein (wet weight basis), and is commonly fed to sheep and goats. Ornamental Plantings The tree is widely employed for shade. In parts of eastern Nigeria, it is planted in avenues along village roads. Mostly, however, it is planted around gardens and homes. Wood The heavy heartwood’s elastic quality makes it useful for axe-handles, mortars, pestles, and pillars for houses and buildings. It is also suitable for carpentry and fine woodworking. As noted, it is not unlike mahogany, and its woodworking qualities and interesting appearance make it suitable for veneers and for fine cabinetwork. Other Uses The bark of the living tree yields a resin used to caulk the inner surface of calabashes and to mend earthenware vessels. The waxy gum is also used as a lamp oil and a salve to treat skin parasites. In southeastern Nigeria, the tree is used as an indicator of the planting season: When butterfruit leaves emerge, it is time to plant the crops. The kernel is said to be useful in dissolving stones in the kidneys. NUTRITION The fruit’s lipid content is extremely high, which is why the tree was initially called “butter tree.” Oil constitutes 33 to 65 percent of the pulp, depending on the tree, its maturity, and the care it received. Dietetically speaking, the oil is a desirable one, being made up of 58 percent unsaturated fatty acids (oleic, 34 percent; linoleic, 24 percent) and 43 percent saturated fatty acids (stearic, 6 percent; palmitic, 37 percent).10 At room temperature (22°C) it separates into a liquid upper layer and semi-solid lower layer, which likely means that the saturated and unsaturated fats are simple to separate. The raw oil has an olive green color, but can be partially bleached to straw yellow. An energy content of 445 calories has been reported.11 10 Ucciani, E. and F. Busson. 1963. Contribution a l’etude des corps gras de Pachylobus edulis Don (Burseraose). Oleagineux 18:253-255. For further nutritional information, see also Kengue, op. cit., and Mbofung, C.M.F., T. Silou, and I. Mouragadja. 2002. Chemical Characterisation of Safou (Dacryodes edulis) and Evaluation of its Potential as an Ingredient in Nutritious Biscuits. Forests, Trees and Livelihoods 12:105-117. 11 Information from T. Silou.
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Lost Crops of Africa: Fruits, Volume III The fruit is also a rich source of protein. Indeed, crude protein constitutes 20 to 30 percent (dry-weight basis). Its amino-acid composition makes it an excellent supplement to cereals and starchy roots. Lysine and tryptophan— essential amino acids deficient in cereals such as maize—are both present in good quantity in butterfruit. The pulp also contains leucine, valine, isoleucine, tyrosine, arginine, cystine, and threonine, all of which are indispensable to human health and often inadequate in malnourished diets. Butterfruit has about half the vitamin C of oranges but other vitamin levels seem unreported. Important dietary minerals are present in useful quantities. The contents of potassium (850-1257), calcium (136-210), and magnesium (129-150) are especially notable. In addition, there is iron (2.3-20), copper (1.1-1.7), zinc (1.1-1.5), and manganese (0.56-1.26). Of note, is the near absence of sodium (1.5 to 52mg/100g).12 HORTICULTURE At present, these fruits are mostly gathered from trees cultivated on farms or in village compounds. In other words, there are few intensive plantings. Although production in orchards and harvests from hedges also occur, most of the trees grow singly in gardens. The plant is traditionally propagated from seeds, which are usually spaced at least 12 to 15 meters apart because of the tree’s spreading habit. The stone is placed flat in a shallow hole and covered with a centimeter or two of earth. In Cameroon, the seed is often planted directly at the foot of a banana tree. Although fresh seeds germinate readily, they quickly lose viability. (Clean ones reportedly remain viable 21 days; those with the pulp attached only 7 days.) The seedlings are transplanted when about a year old, at the beginning of the rainy season. Vegetative propagation has long been considered very difficult. ICRAF researchers at Onne, Nigeria, however, have developed methods for air layering the plant.13 Budgrafting with juvenile budwood is also possible.14 On a farm or in a village, young trees are commonly trimmed to a manageable size for easy harvesting. The species’ ability to take heavy pruning is also desirable in agroforestry because farmers can cut it back to reduce the shade cast on crops growing nearby. 12 All figures are mg per 100g. Silou T., D. Mampouya, L.W.D. Loka. and M. Saadou. 1999. Composition globale et caractéristiques nutritionnelles des huiles extraites de 5 espèces des cucurbitacées du Niger. Rivista Italiana della Sostanze Grasse 76:141–144. 13 In 2002, ICRAF, with headquarters in Nairobi, changed its name from the International Centre for Research in Agroforestry to the World Agroforestry Centre. 14 Information from J.C. Okafor.
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Lost Crops of Africa: Fruits, Volume III A difficulty is that these trees come in two “genders”: female trees that regularly produce heavy fruit crops and male-hermaphrodite trees that either never produce or produce a small crop irregularly. Unfortunately, only a quarter of the natural population is normally female and three-quarters of the population are therefore useless for food production. Vegetative propagation provides the opportunity to multiply the female trees, especially ones with desirable traits. HARVESTING AND HANDLING The fruits are ripe when they have darkened from pink to blue/black. Hand picking typically occurs in the morning, with men or boys climbing into the trees and using hooked poles to draw the fruits within reach. Mature ones are packed into bags (holding up to 10 kg) that are usually hung on a branch. When filled, the bags are lowered on a rope to the ground. Once picked, the fruits become quite perishable. In the oppressive heat and humidity of tropical lowlands, they do not keep much more than a week. Storage in a cool and airy spot, preferably a basket, helps. Deterioration occurs through moisture loss and the fruit consequently shrivels. Dampness is especially to be avoided; it causes the fruit to soften faster and turn moldy. For this reason, butterfruit is not harvested on rainy days. Similarly, it cannot be packed densely or stored in airtight containers such as plastic bags. LIMITATIONS The cropping system, which is mostly traditional and unsupported by scientific verification, seems to have two major constraints: Most stands have too many male trees and the females themselves are too variable— oftentimes every tree bears fruits of different size, character, and quality, making them hard to handle and market. Farmers report that many trees do not bear regularly. So far, no clear-cut pattern has been detected. The problem may be due to a genetic predilection toward alternate bearing. It may be due to high temperatures (anything above 23°C is thought to reduce fruit set and yield). Or it may be due to pollination failure (perhaps caused by heavy rainfall at flowering time). In addition, it is reported that some trees drop most of their fruits at an early stage of development, which could be due to a nutrient deficiency in the soil. Currently, the species is strongly seasonal, fruiting during the wet season when other fruits are abundant. Also, the fruiting season is short. Post-harvest losses can be enormous. In addition to shrinkage and rot, the fruits invisibly lose nutritional value.15 Part of the problem is caused by bad harvesting technique: resulting in rapid deterioration. 15 In one microbiological investigation, such losses were caused by Botrydiplodia theobromae, Rhizopus stolonifer, Aspergillus niger, and Erwinia spp. The first two species accounted for most of the damage. Information from J.C. Obiefuna.
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Lost Crops of Africa: Fruits, Volume III NEXT STEPS This crop seems capable of tackling problems of the poor, of the malnourished, and of the land. It can become a basis for rural development. Obviously, a productive, high-energy, high-protein food like this is worth developing. Now that better growing techniques are known, governments, individuals, and organizations throughout its range should get involved. Steps to achieve better use of the species’ potential include the following. Increased Trade Already butterfruits enter commerce within and between Central and West African countries. But that commerce can be enlarged and made more efficient. Nothing would help this crop’s further advancement more. Any increase in “demand pull” will see farmers and traders leaping in to produce and sell more butterfruit. Malnutrition Trials As noted, the more extensive use of butterfruit in Central and West Africa could be a good thing solely on nutritional grounds. Its combination of high protein, high energy, and good mineral profile makes it a promising weapon for fighting malnutrition. Now is the right moment to test its potential as a lifesaver for children, nursing mothers, and the desperately sick. In particular, the extracted pulp cake might make a useful nutritional supplement. Protein content is lower than common oilseed cakes such as peanut, safflower, and soybeans (ranging from 30-50 percent), but richer than maize, rice, sorghum, and wheat (all 15 percent or less). Food Security Assessment As noted, people in southeastern Nigeria rely on butterfruit to survive the hungry season. This phenomenon and its replicability elsewhere deserve investigation. Increased Planting This species is a promising candidate for organized production on an organized scale. Programs to mass produce selected plants and distribute the planting materials to farmers could be especially helpful. In this way, the health and welfare of the people—especially children, the elderly, and the poor—will be improved. Horticultural Development This highly variable plant is about where the avocado was a century ago: it suffers from a lack of target types upon which to build horticultural production. The discovery of the equivalent of the ‘Fuerte’ avocado16 will quickly change the situation. The lack of organized selection or improvement seems largely due to neglect. With more detailed studies, many bottlenecks and difficulties will undoubtedly disappear. 16 Selected from a California backyard in 1905.
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Lost Crops of Africa: Fruits, Volume III Among horticultural practices needing development are those for: Reducing premature fruit drop (abortion); Changing the “gender ratio.” Whereas a dioecious species like this typically needs only a handful of male plants for every 100 females, plantings in Nigeria have proved to have up to 80 males. Improving pollination. The floral biology and the mechanism of fertilization need investigation. This likely will help not only improve fruit-set but the breeding and improvement of the species. Males supposedly produce their pollen poorly and irregularly, but reliable males that shed their pollen at the right time for the local female trees must surely be around; Fruiting out of season. Butterfruit would rise in significance if the crop fruited a few months earlier or later. This is not a far-fetched notion. In southeastern Nigeria, for instance, forms that ripen several months after the normal season have been observed;17 Reducing pests and diseases; Improving field management. Better practices, alone, will result in better yields and more extensive cultivation. Rejuvenating old, but good-quality trees; Dwarfing. As with apples, creating smaller plants would make the butterfruit more manageable. Already, it is known that pruning seedling trees to a height of 1-1.5 m produces dwarfing.18 Gathering the Diversity This species offers a huge range of genetic diversity. Selection for such things as fruit size, pulp thickness, fruit quality, taste, seed-oil content, tree height, and fruiting season all offer promising possibilities for horticultural progress. Germplasm collections—both wild and in cultivation—are needed to preserve the range of variation. Special attention should be paid to collecting germplasm in the species’ West/Central African region of genetic diversity. Propagating Select Forms Making selections from the species’ diversity is crucial to the crop’s future. Vegetative multiplication will lead to plantations of highly productive clones, which would transform this crop almost overnight. The plant has so far resisted many classical vegetative propagation techniques, but much more effort along these lines is warranted. Fatty Acid Composition Among the many things to select for is polyunsaturation in the oil. The fatty acid composition varies significantly between plants and maybe between countries. Samples gathered in Cameroon, Congo-Brazzaville, Congo-Kinshasa, and Gabon, for example, 17 Normal types ripen June-August; late types November-January. 18 Information from J.C. Okafor.
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Lost Crops of Africa: Fruits, Volume III have shown the following ranges: palmitic acid, 41-47 percent; stearic acid 2-3 percent; oleic acid 20-34 percent; and linoleic acid, 19-29 percent.19 Diversifying Uses That a food so rich in protein and lipid has not been seriously investigated is surprising. Their functional properties deserve assessment to determine the breadth of possible uses in a wide variety of different industries. While not showy, the flowers are strongly perfumed and attract masses of pollinators. According to one account,20 more than 80 percent are honeybees. Thus, butterfruit may well be a valuable honey tree. Nutritional Research As mentioned, butterfruit seems likely to be very effective for feeding malnourished people. The traditional practice of eating the fruit together with maize, cassava, or plantain should be encouraged. The fruit’s low carbohydrate content makes it a good supplement to those carbohydrate rich foods. Because it helps make up deficiencies in minerals and essential amino acids, the fruit neatly balances the starchy staples in the daily diet. It also contributes considerable food energy. Needed are more measurements on the nutrient content of the many different varieties. Also needing documentation are the ways the fruit is used in traditional diets. Given that information, means for improving and modifying local diets can be determined more precisely. Food Technology Tropical conditions give a fruit as perishable as this one a short shelf life. Post-harvest storage is one key to its greater commercial use. Refrigeration is an obvious possibility; few technical details have yet been reported, but trials indicate that lower temperature does increase the fruits’ storage life. Means for reducing post-harvest losses— including pest- and disease control—would be useful. Pickling and other preservation methods should be tried as well. These could help make the fruit available out-of-season, and especially in the “hungry season” when nutrients such as this fruit provides are hard to find. Nutrient losses using various storage, processing, and preservation techniques also need detailing. Reforestation Trials The tree has potential for use in environmental-improvement programs confronting such issues as soil erosion, the stabilization of reclaimed gullies, urban beautification, and the provision of shade for parks, paths, roadsides, schoolyards, and bus stops (especially those where children gather). Given the tree’s many uses, it can contribute both environmental benefits and food for the needy. 19 Information from T. Silou. 20 Giacomo, R. 1982. Biologie florale du safoutier (Dacryodes edulis) au Gabon. Rapport du projet FAO/CIAM, Libreville, Gabon.
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Lost Crops of Africa: Fruits, Volume III SPECIES INFORMATION Botanical Name Dacryodes edulis (G. Don) H.J. Lam Family Burseraceae Synonyms Pachylobus edulis, Pachylobus edulis var. mubafo, Pachylobus saphu, Caharium edule, Canarium mubafo, Canarium saphu, Sorindela deliciosa Common Names Bantu: bekwa (Banyangi, a subgroup of Bantu origin) Benin: orumu Cameroon: plum (pidgin), sibakwbri (Bakweri), sa (Beti), sa (Ewondo), tsem (Bamiliké), assa, tchou, letse, sau, say (Oroko) Central African Republic: sene (Tonga), bukoe (Kitembo) English: African pear, African plum, bush butterfruit, eben tree, native pear, bush mango French: safoutio, le safoutier (the tree); safout, prunier (the fruit) Nigeria: iben, ube, oibo (Ibo), elemi (Yoruba), orumu (Edo), eben (Efik), boshu (Boki), orumu, (Urhobo), oromi (Afemai) Congo: safou, nsafou (Kikongo and Lingala), osaw Description The butterfruit tree is commonly 8-12 m high when grown under cultivation in the open, but up to 45 m in the forest and in old plantations. The trunk is generally cylindrical and straight. Although it can reach 1.5 m in diameter, it is normally much smaller. The plant has compound leaves with 4-12 pairs of leaflets (odd-pinnate; with a single terminal leaflet). It is deciduous, losing its leaves in the dry season. Although the species has male and female flowers on separate plants, there are hermaphrodite (male/female) trees as well. Male flowers are larger (8-25 cm long) than female (5-15 cm long). At least in some vigorous inflorescences, the terminal bud forms the flowering shoot for the following year. Only female flowers produce fruit of course. Although the amounts vary, female inflorescences tend to be very productive. Hermaphrodites are less productive. The fruit is ellipsoid, globular, or conical; 4-15 cm long, 3-6 cm in diameter. It is rose pink to white when young, deepening to blue, purple or even black at maturity. The pericarp, which represents half the weight of the whole fruits, consists of a thin, waxy, and colored epicarp and a pulpy mesocarp that is light pink, rose, light yellow, light green, or whitish in color. This pulp varies in flavor depending on the tree.
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Lost Crops of Africa: Fruits, Volume III Distribution Gabon appears to be the center of origin for the genus Dacryodes; among the 19 species that occur in Africa, 11 are found there.21 Dacryodes edulis seems to originate in the humid intertropical regions of southern Nigeria, Congo, and Cameroon. As noted, it is cultivated throughout West and Central Africa: the Gulf of Guinea, the interior basin of Congo, Cameroon, Congo, Gabon, Nigeria, Uganda, and central Angola. Horticultural Varieties There are no named cultivars but, botanically speaking, the species involves at least two distinct varieties:22 Dacryodes edulis var. edulis has large fruit, usually more than 5 cm long by 2.5 cm wide; Dacryodes edulis var. parvicarpa has small, more or less conical fruit, usually less the 5 cm long by 2.5 cm wide. Environmental Requirements Most of the world’s oil-bearing plants are confined to narrow ecological areas. (Oilpalm and coconut, for instance, are restricted to hot and humid areas.) Butterfruit, however, tolerates several. It thrives, for example, in all the ecological zones of Nigeria and Cameroon except the very dry northern provinces. Although it fits well into savanna zones, its fruit production is greatest in the humid forest zones. In general, performance is best in the shade and in good soil. Rainfall The plant tolerates rainfall from 600 mm to 3,000 mm and more. By some accounts, low humidity at flowering time may frustrate fruiting. Altitude Low-medium elevation, from sea level to 1,500 m. Low Temperature Unknown. One contributor reports the minimum at his location as 9°C (in January). Possibly the plant requires “low” night temperature for uniform flowering (22°C or 14°C have been suggested). High Temperature Thrives where temperatures top 40°C. 21 Aubreville A. 1962. Flore du Gabon, No. 3: Irvingiaceae, Simaroubaceae, Burseraceae. Museum. National d’Histoire Naturelle, Paris. 22 J.C. Okafor described two varieties, both of which are cultivated (though var. edulis is preferred on account of large size). Okafor, J.C. 1983. Horticulturally promising indigenous wild plant species of the Nigerian forest zone. Acta Hort. 123:165-176
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Lost Crops of Africa: Fruits, Volume III Soil Seems not to present a limitation. The species has been reported growing on oxisols, ultisols, loamy clay, sandy clay, humic ferralitic soils, deep loam rich in organic matter, andosols, and ferriginous (chalybeate). Related Species Currently, 19 Dacryodes species are recognized. None of the others has received even the pitiful amount of research accorded the butterfruit. Yet some species produce edible fruits. They, at least, deserve at least preliminary investigation. Examples are: Dacryodes buettneri (Gabon). Large and important timber tree; Dacryodes igaganga. Another large and important timber tree; Dacryodes klaineana (Sierra Leone; common name “damson”). Fruit juicy with a taste said to be “deliciously sweet/sour”; and Dacryodes macrophylla. Fruit also juicy and “deliciously sweet/sour.”