EGGPLANT (GARDEN EGG)
Late in the 1500s British traders introduced London’s greengrocers to a strange new vegetable they’d picked up along the coast of West Africa. By 1587 this so-called “Guinea squash” was on English dinner tables. Although eaten as a vegetable, it was actually a small fruit about the size of a hen’s egg. It was the same color as a hen’s egg also. This pure white ellipsoid made an eye-catching eatable, which for obvious reasons the public soon dubbed “egg-plant.”
At roughly the same time another vegetable also appeared in Britain. This one had fruits nothing like eggs. They were much larger, deep purple in color, and irregularly misshapen. For all their differences, though, the two plants were botanically related and shared common culinary characteristics.
For a while both were used. Eventually, however, the Guinea squash lost its toehold, and fell out of Western cuisine. The newcomer, on the other hand, not only survived but also took over its predecessor’s felicitous name. This is how a purplish blob, looking like no egg seen since perhaps the dinosaurs, came to be misnamed “eggplant.” The interloper1 that stole an African plant’s good name hailed from Asia, where it has been cultivated more than 4,000 years. In the Far East it even now holds a position comparable to that of tomato in other parts of the world. Indeed, it is sometimes referred to as “Asia’s tomato.”2
In recent centuries this versatile purplish vegetable has gone global in a big way and is now part of virtually every cuisine. It is fried, grilled, roasted, boiled, seared, baked, steamed, mashed, pickled, stir-fried, pureed, and otherwise prepared by many peoples. To give just a smattering of examples: Greeks, Italians, Syrians, and Egyptians all feature eggplant as daily fare. However, in the love of this bland and humble food none surpass the Turks, who claim to know a thousand ways of preparing it.3
This worldwide popularity is something of a mystery. Lacking in nutritional quality, high monetary return, or even flavor, the eggplant has in some strange way insinuated itself into myriad local specialties. Indeed, it is the heart of famed national dishes, including: moussaka,4 baba ghanoush,5 ratatouille,6 and Imam bayaldi.7 And Sicilians, who certainly know a thing or two about fine dining, rave over caponata.8
Because of the general trend toward ever-greater reliance on vegetables and on diversity in diets, the enigmatic eggplant is growing in global popularity faster than ever. Already, it has taken firm hold as a meat substitute. Popular vegetarian dishes now include such things as eggplant Parmesan, eggplant lasagna, eggplant curry, and even eggplant chili. The vegetable also lends splashes of purple to trendy modern sautés, ragouts, pizzas, or vegetable Napoleons.9 It has even become big in the self-styled capital of cuisine: New Orleans.10
While this culinary juggernaut commandeered the world of cuisine, the original eggplant—the Guinea squash—was left to languish. Four centuries later it remains unknown to the West and to modern horticultural science. Yet it too possesses an array of gastronomically interesting qualities. It, too, could be a globetrotter, not to mention a much bigger contributor to Africa’s own food supply.
Although used like its Asian cousin, Africa’s eggplant is quite different in appearance. Most of its fruits are sized and shaped like eggs. Indeed, many are reminiscent of a pointy tomato, a species to which they are so closely related that they can be considered Africa’s answer to South America’s tomato.
This is among the most appealing vegetables the eye can see. Few others boast such rich colors. Among Africa’s overall eggplant diversity it is possible to find fruits in white, cream, yellow, green, lime, orange, pink, red, plum, burgundy, lavender, violet, purple, or dusky black. Many come striped and multi-colored. And all possess a glossy skin that tends to shimmer in the sunlight. Beyond being egg-shaped, they can be also round, flat, ribbed, and pumpkin-like. Some get to be as imposing as beefy tomatoes; in general, though, they closely emulate chicken or duck eggs in size. Most start out white, and are normally eaten before exposing any hint of the final color they will ripen into.
Because the taxonomy of the different African eggplants is too complex and uncertain to bother with here, we have chosen to highlight a single
species, Solanum aethiopicum. In fact, we highlight only one of the four groups recently identified within that species (although much of what is said applies to all African eggplants). In English, fruits of this so-called Gilo Group go by names such as scarlet eggplant, mock tomato, garden egg, garden huckleberry, or gilo. They are the most widespread eggplants cultivated in Africa, and can be found from southern Senegal to Nigeria, from Central Africa across to eastern Africa, and from Central Africa south to Angola, Zimbabwe, and Mozambique. And they are almost certainly the original “Guinea squash” Londoners were admiring 500 years ago.
Many gilo cultivars have fruits that are delicious raw—both when immature and fully ripe. They can be chewed, sliced, or pureed into juice and eaten fresh like tomatoes. Depending on type, some are sweet, others bitter (a feature many Africans prefer in a vegetable). At a glance, those in the know can distinguish the sweet cultivars, whose fruits possess smoother skin and a more evenly rounded profile.
Despite international obscurity, this is a resource of considerable economic importance. Throughout Africa local garden eggs are very popular and play an important part in many diets. They have a long storage life (up to three months) and transport well. They are also often dried for use later in the agricultural cycle when fresh foods are unavailable. They (as well as the leaves of some cultivars) provide a reliable and continuing source of income for millions of farmers, most of them women. In rural districts from Senegal to Mozambique, a common sight is women hefting baskets of garden eggs on their heads to sell in nearby villages or townships. The crop is mostly grown, harvested, and marketed close to home, and it forms a crucial part of both the rural economy and the female existence.
The plants are notable for yielding a lot from a little space. They can produce a profit from the tiniest plots; even a few plants grown in garden pots can provide a worthwhile harvest. The plants are easy to raise, relatively free of disease and pests, and provide a steady supply of both food and income.
Like their famous Asian cousin, these vegetables seem at first sight to be hardly worth attention. They are mild in flavor and not especially nutritious. And they certainly don’t light up the meal on the dinner plate—once cooked they usually end up a brown and squishy mass.11
Clearly, though, this country cousin of a booming global resource should not be left languishing in the scientific wilderness. Because it remains largely unsupported by research, it nowadays falls far short of its potential. At present only a handful of researchers are championing its cause, but this small group is enthusiastic about the crop’s promise. Given attention, they say, Africa’s own eggplant could achieve a very big future. And they are
right: In this neglected vegetable there is a whole new world of colors, textures, flavors, and culinary uses to explore and exploit. If the common eggplant provides any guide, the African counterpart offers a foundation for myriad flavors, textures, and ingredients in meals celebrating dozens of local traditions, cultures, and food combinations.
Why should Africa invest time and effort on these crops? Beyond the reasons referred to above lie further justifications. The plants, for example, are very adaptable and can be grown in widely different climates. They are fast maturing and yet can be harvested over a period of time, so they yield both quick results and extended ones. They could notably benefit soil conservation activities, especially when used to quickly cover bare soil in the spaces between the farm’s main crops. They tend to tolerate shade and so can be fitted in around various taller plants, such as bananas, cassava, and trees.12 They are suited to infertile sites and benefit various difficult soils, and are likely candidates for wringing income from numerous kinds of “agricultural wastelands.”
Because of their partiality for small spaces, this is a crop for city gardens squeezed in among the structures of modern life: high-rise buildings, factories, shanties, roads, train tracks, and chain-link fences. This is already apparent in African cities. A survey in Dar es Salaam, for example, found that the most frequently grown non-leafy vegetables were (in order of importance): tomato, common eggplant, African eggplant, sweet pepper, hot pepper, okra, cucumber, and carrot.13
To sum up: The local garden eggs are significant vegetable resources almost Africawide. They are good for nutrition, rural income, and soils. They are high yielding, easy to grow, and simple to harvest and handle. They are vital to local cuisines, local economies, and local cultures. They have untapped potential waiting to be brought out by research. In many parts of Africa there is considerable scope for producing much better varieties in much better quantity. They also have notable market potential and could become the cornerstone of localized rural economic development. And there is even potential for exporting African eggfruits to Europe and North America and earning some hard currency.14
One study (in Java, where these African eggplants are known) showed that 35-60 percent shade does not affect the edible yield of the species.
The authors found that the leafy vegetables being most commonly cultivated in Dar es Salaam were: leaf amaranths, sweet potato leaves, pumpkin leaves, cassava leaves, cowpea leaves, Swiss chard, chinese cabbage, African kale (Brassica oleracea var. acephala), and nightshade (Solanum scabrum). Leaf amaranth is dealt with in Chapter 1; okra in Chapter 16.
Caribbean nations already export African eggfruits to Europe under their local name “anthora.”
Humid Areas Excellent. The African eggplant species are generally resistant to the molds, mildews, and other fungal scourges that achieve their greatest development in the lowland tropics’ heat and humidity. According to reports, they even show resistance against some of the worst soil-borne plant pathogens—including Fusarium oxysporum and Verticillium dahliae—and may have potential as tools to avoid soil sickness (see later).
Dry Areas Good. These plants are moderately drought resistant, and with them irrigation is rarely needed. The exact level of drought tolerance is untested, but African eggplant is known to survive dryness better than the Asian counterpart.
Upland Areas Probably excellent. These perennial plants are virtually always grown as annuals, and with their fast maturity should fit well into many climatic niches with abbreviated growing seasons.
Garden eggs are already commercially grown in a few other places— notably Brazil, the Caribbean, and Southeast Asia. The Internet carries guidance on growing them in Britain.15 We see no reason why this species cannot expand in global scope, although uncertainty fogs the exact extent of its adaptability to cooler climes.
There are two food products from these plants, fruits and leaves.
Fruits Typically in Africa, the garden egg is chopped, cooked and mixed into a variety of vegetable, meat, or fish stews and sauces. Although bitter taste is a major characteristic, many African eggplants are sweet or bland, especially in the immature stages in which they are eaten. The unripe fruits are usually cooked in a sauce after being chopped, parboiled, ground, or otherwise prepared. Peeling is unnecessary because the skin becomes tender enough to be consumed along with the rest. They are among the few vegetables that reach full flavor only after being cooked beyond the crisp stage.
Leaves Africans eat the leaves of at least certain types of the Gilo Group eggplants. Although these leaves are high in solanine, which is toxic,
cooking apparently renders them harmless.
Ornamental Uses Not too many vegetables can take your breath away just with their looks. But African eggplants can. The fruits come in types that can be very ornamental, gleaming in more colors than the rainbow. The plants themselves are attractive small bushes that can be light or dark green, or purple, with tiny to very large leaves.16
These fruits are far from nutritional powerhouses—they contain 92 percent water, after all. Nonetheless, they also contain small amounts of protein, vitamins, minerals, and starch. They are moderate sources of beta-carotene, B vitamins, and C. They also contain calcium, iron, potassium, and probably other minerals.
By the standards of the modern Western world, this veggie is a diet-doctor’s dream: low in sodium, low in calories, high in dietary fiber, and a good source of potassium. It is used as a meat substitute not because it is high in protein, but because its spongy texture easily absorbs the other food’s flavor while providing a mouthfeel vaguely suggestive of the presence of meat.
The seeds scattered through the fruit also contain vitamin C and carotene and other nutrients.
The leaves are excellent sources of vitamins A and B (particularly riboflavin), calcium, phosphorus, and iron. They contain about 5 percent of a protein containing significant amounts of methionine, one of the essential amino acids most difficult to find in plant-based foodstuffs.
This crop is mostly grown on a small scale in compound gardens. It likes full sun, well-drained soil, or raised beds.
Propagation is by seed, which can be broadcast or drilled directly into well-prepared ground. Typically, however, the seeds are first sown in boxes or nursery beds. Germination takes about a week. After a month, when seedlings are 5-10 cm high, they are transplanted into the garden beds. The plants take at least a further month to establish themselves, after which they develop strongly.
For fruit production, plants of the Gilo Group are typically spaced 1 to 1.5 m apart. This spacing allows for the vigorous horizontal branching of these deciduous shrubs, which grow 1m tall unpruned.
Although less susceptible to disease than many vegetables, the crop is
attacked by a fungal leaf spot and by several insect pests, including leaf beetle, moth larvae, bud borer, and sucking bugs. (The plants are normally grown during the rainy season, solely to avoid the pests that build up during dry weather.)
The plants branch profusely, a feature making weeding difficult. In time, however, this propensity itself helps by shading out most competitors.
HARVESTING AND HANDLING
The perfect eggplant is picked while still immature—about 70-90 days after sowing. At that point the skin is glossy and firm, the flesh white, and the seeds tender and fully edible. It is best to use a knife or pruning shears to cut the fruits from the plants. Harvesting continues over a period of 8-10 weeks. Yields vary, but in one test, three plants (grown on a small plot 1m x 4m) produced 10 kg of fruits.
The production of leaves usually involves different horticultural techniques. In this case, the plants are severely cut back to a height of not less than 5 cm after which a massive growth of young shoots occurs. Regular harvesting of the young shoots and debudding encourages the production of side shoots that extend the harvesting period. A total of five to eight weekly harvests are usually possible.
The post-harvest handling of the fruits has not been thoroughly evaluated, but the only unusual challenge noted is a rapid browning of the skin after harvesting. Growers currently minimize this by picking fruits gently and in the cool of the day, avoiding exposure to the sun, and—where possible—putting in cool storage for a few hours, but many tricks undoubtedly remain to be learned.
The very thought of growing African eggplant is likely to raise hackles in some quarters. Its flowers betray its relationship to a notorious weed that adversely affects some of the world’s main crops—the small, bell-shaped, purple bloom is utterly nightshade. Indeed, the whole plant looks like the black nightshade, Solanum nigrum.17 For this reason, it will be difficult to promote it as crop plant in, for example, the United States, Canada, New Zealand, Britain, or Israel. Of course, the common eggplant is not problematic in those countries, but people bringing in its cousin will find the guilt-by-association with a more distantly related weed hard to overcome.
The Solanaceae (or Nightshade Family) is renowned for protecting its leaves with lethal compounds. The toxins occur to greater or lesser degree, depending on the species and the parts of the plant. Some solanaceous
species have perfectly edible parts but, despite all the evidence of their safety, people typically fear the worst. When the common eggplant was first introduced to Europe, botanists prophesied that consuming it would cause insanity.18 Potato, tomato, and peppers—all of which are nightshade
relatives—were in their time claimed to be deadly too.19 African garden eggs can expect the same.
A third misunderstanding likely to limit support for African eggplant has to do with the crop’s public image in Africa, where it is seen as a low-status vegetable associated with poor people. As evidenced by poor-person’s crops before it—potato, soybean, peanut, pea, oats, and barley, among them—this mindset can hold back a truly exceptional new food for decades or forever.
The garden eggs (like the common eggplant) must be harvested at just the moment when the fruits have developed full size and still remain firm to touch. If they are left to mature, the skin turns dull, the flesh spongy, and the seeds turn hard and dark. Prompt picking also increases fruit set and boosts overall yields.
For all intents and purposes, African eggplants have received no production research. Most national agricultural research or extension systems allocate no personnel or resources to these vegetables, which they generally consider low-priority species. This needs to change. Agriculture schools and farming programs across Africa should initiate localized eggplant support and improvement projects.
In addition, public interest in the greater use of garden eggs needs to be kindled. Indeed, these veggies could quickly fit into development-support programs across the continent—programs dealing with such things as urban agriculture, soil protection, traditional foods, home gardens, sustainable development, women’s welfare, and rural development.
There is also a need to foster optimal cultivation practices. This is not a call for delay and long-term research operations; instead, it is a suggestion to take whatever knowledge is already available and make the most of it. In this regard, indigenous knowledge on the plant types used in the various countries should be gathered. Socioeconomic surveys on the production and use of garden eggs in traditional settings across Africa are warranted as well.
Programs to provide bulk samples of quality seed might also be helpful in promoting the greater appreciation for a neglected crop that is under almost everyone’s nose.
Organizational Support At present, the exchange of eggplant germplasm and related information occurs mostly via accident and personal contacts. In practice, only a small part of the potential knowledge and germplasm is available to agronomists, vegetable breeders, growers, and whatever seed organizations exist.
As backup support, it would be good to have some sort of functioning African-eggplant promotion and coordination undertaking. This need not be elaborate or even formal—funding in this case being less important than any kind of forward movement. But a fiscal means for sustaining interest and providing specific help and stimulation would be exceptionally supportive.
One thing to be done is to gather the natural diversity of eggplant across Africa. As noted, the types to be found are amazingly varied. A start on this has been made already, and seeds of several different types are housed in the vaults of international seedbanks. But local initiatives can still do much to gather the germplasm in the exceptionally diverse and dispersed habitats, not so much to conserve it but to get the best into wider use.
Another thing is to establish an eggplant database, into which research information could be incorporated, and subsequently disseminated to farmers, researchers, and interested amateur gardeners. Accurate and illustrated botanical descriptions of the local ‘cultivars’ used as vegetables could also be useful.
Food Technology In the advancement of this neglected resource, there are many things to capture the interest of food technologists. For one, African eggplant should be tested as a substitute in recipes developed to exquisite perfection for its famous Asia-born counterpart in countries such as Greece and Turkey.
For another, although no specific mention of toxicity has been reported, this species belongs to a genus some of whose many members have poisonous leaves and sometimes also unhealthy fruits. This is now the time to clarify once-and-for-all the African eggplant’s potential for disaster.
For a third, the whole issue of post-harvest handling of the fruits deserves to be analyzed and formalized.
Horticultural Development The species can be considered an almost-blank agronomic slate, and almost any studies relating to its production—from seeding depth to thinning the fruits to increase their size—merit clarification. Horticultural investigations are especially needed to determine the field conditions that promote optimal growth and maximal harvests.
Genetic Development There are excellent chances for genetically enhancing African garden eggs for increased yield and other features through simple selection and/or plant breeding (perhaps including hybridization). There is a need to create (or identify) varieties better adapted to specific growing conditions. In addition, there is potential to create varieties with fruits of even more shapes, colors, and tastes.
Fuller use of genetic diversity can also raise public and industry’s use of the crop. That, in turn, will lift its commercial value and profile.
In biotechnology exist many other possibilities. Breeders can likely take
advantage of the advances made in related solanaceous species. For instance, genetic maps of potato, tomato, peppers, and the common eggplant are available. Markers common to African garden eggs and those well-mapped Solanaceae should be identified. Such markers should allow the molecular tagging of agronomic traits and provide powerful tools for breeding whole new worlds of African eggplants.
Genes for Improving Other Crops Because of their genetic closeness to major global crops in the Solanaceae, African eggplants may also provide powerful tools to the breeders of such things as tomato, potato, and eggplant. They contain several traits potentially useful in improving those crops. These include resistance to:
atrazine (a herbicide);
tobacco mosaic virus;
potato late blight;
phomopsis fruit rot; and
Genes for these might possibly be isolated from Africa’s garden eggs and genetically engineered into eggplant, potato, tomato, and peppers.
In addition, the species has been reported as showing molluscicidal activity, and may prove useful in controlling garden snails, slugs, or maybe even the water snails that harbor lifestages of the schistosomiasis parasite.20
Moreover, it has been claimed that this crop serves as an alternative host for a variety of pests, bacteria, and fungi that affect a number of commercial crops. African eggplants might therefore be used to lure away the pests.
As noted earlier, there are indications that African eggplant is resistant to soil-borne diseases caused by the very serious pathogens, Fusarium oxysporum and Verticillium dahliae. Perhaps it has a potential to be used as a way to avoid soil sickness.21 Scientific exploration is well warranted.
New Locations Should the outside world try African eggplants? We think yes. The crop already grows in Brazil, and its potential for other tropical countries is high. It may even prove successful in Mediterranean nations. Those are also the ones that rely on eggplant, and they may find the extra drought-tolerance of the African version notably valuable.
Exports and Marketing Within Europe and the United States, there is a strong tendency toward horticultural diversification, not only in the size, shape, color and taste of the well-known fruits and vegetables, but also vegetables that are new to the markets. Furthermore, some new eggplant species could be introduced to satisfy the consumers’ continual demand for novelty products.
Taxonomic Clarification Solanum taxonomy has been clarified and resolved so often that outsiders have almost lost faith. African eggplants offer a world of possibilities for overcoming taxonomic difficulties in this important family because they lie somewhere among potato, tomato, peppers, and the common eggplant. DNA and other sophisticated evidence might clarify and resolve the uncertainties all over again.
Botanical Name Solanum aethiopicum L.
Synonyms Solanum gilo Raddi, Solanum olivare Paill. & Bois. Solanum pierreanum Pailleux & Bois.22
Family Solanaceae (Nightshade Family) section Oliganthes
Arabic: begingan et gut a
English: mock tomato, scarlet eggplant, Ethiopian eggplant, African bitter pea-aubergine, wild pea-aubergine, wild African aubergine, tomato-fruited eggplant, Ethiopian nightshade,
French: tamate amere, aubergine amère, petite bringelle maronne (Africa)
Nigeria: asun (Shum group), ikan, igba (Gila group)
Sudan: guta, quta, begingan et gut a (Ar)
Uganda: nakati, nakasuga (Lug), abugarra (Yr/Tr), (n)jagi (Ach/Gis), enjagi, entura (Yr/Tr/Kig), etanga (Ank)
Chinese: Xiao gu qie, Xiao ku fan qie (Cantonese)
In the vegetative stage, a plant of the Gilo Group looks like a common eggplant (i.e., Solanum melongena). It is a fairly woody deciduous annual, or occasionally perennial, herb up to 100-150 cm tall. It is not prickly. The
mature leaves are smooth, apart from minute glandular hairs. Features distinguishing it from the other species are the small, white, star-shaped flowers. In addition, the calyces are never long and the inflorescence has a short (1 cm) rachis. The fruits are 3-6 cm in diameter, varying in shape from ellipsoid to almost round. They contain 2-6 locules and are normally firmly attached to thick fruit stalks that turn downwards. The flowers are pollinated by large bees.23
Within Africa The plant occurs in virtually all of sub-Saharan Africa, but is less well known in (maybe absent from) South Africa and Madagascar.
Beyond Africa Centuries ago, the plant was taken to Brazil, probably with the slave trade. Brazilians call it “gilo,” a slight corruption of the name used in East Africa, ngilo.
There are few named varieties, perhaps better called local landraces.
The crop’s ecological requirements are thought to be much like those of common eggplant, although Solanum aethiopicum is probably slightly hardier, and more tolerant of drought.
Rainfall 500-1200 mm or more. The plants thrive during the rainy seasons in the tropics.
Altitude Up to 1200 m.
Low Temperature Optimal temperatures for the growth of these plants lie between 20 and 30°C, and perhaps higher, but the species likely will grow well at temperatures down to 15° C. (The optimum germination temperature lies between 15 and 30°C, although temperatures fluctuating between these values are apparently required to break the seed dormancy.)
High Temperature The species seem to grow well within an upper temperature of 35° C.
Soil An easily grown plant, it succeeds in most soils. Nonetheless, it does best in soils of high fertility, especially those high in nitrogen and phosphorus. Sandy loam to friable clay soils with a pH range of 5.5 to 6.8 have been declared “particularly suitable.” However, one report from Britain notes that “providing the soil is well drained, the actual soil type appeared almost irrelevant to good growth.”
Photoperiod Believed to be day neutral.
Gboma eggplant The present chapter has focused on the gilo eggplant, Solanum aethiopicum, but it might well have dealt with this gboma eggplant, Solanum macrocarpon. The two are similar in all but a few details of the flowers and leaf hairs. Virtually everything said in this chapter is true also for the gboma eggplant.
This is another species that might be more widely and more intensively cultivated than at present. It is perennial, glabrous, and shrubby. Originally from tropical and equatorial Africa, but widely introduced into Southeast Asia, this species produces a small fruit similar to the eggplant. The fruits may be eaten when very small, often raw, but in many places the plant is grown chiefly for its edible leaves.
Truly lost “eggplants” In West Africa can be found Solanum scabrum L. and S. americanum Mill. The leaves of these two wayside plants, along with many other Solanum species, such as S. nigrum from the Americas, form the ubiquitous “African spinach”, important (but potentially toxic) food resources that only recently have drawn the attention of scientists.
Close cousins There are, as noted, relatively distinct groups within the species Solanum aethiopicum.24 Those with special potential are:
The Shum Group. This has fairly small, subspherical fruits and small glabrous leaves. Only the leaf is used (the fruits being too bitter). It is distributed throughout Central Africa, as well as in western equatorial Africa, Nigeria, Benin, Togo, and Ghana.
The Kumba Group. This has much-lobed glabrous fruits that are pumpkin-shaped and only slightly bitter. When ripe, they are light green to red-orange—very ornamental and unusual looking with lots of bumps. Both leaves and fruits are eaten. The species is restricted to the sub-Sahelian region from Senegal to the top of Nigeria—a coverage reflecting that of the old Mali Empire.