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Lost Crops of Africa: Fruits, Volume III
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Lost Crops of Africa: Fruits, Volume III 8 MELON The melon (Cucumis melo) is one African fruit that is already known around the world. All the warm regions produce it, and every day millions enjoy a melon for breakfast, lunch, or dessert. Certain countries—among them Iran, Pakistan, Japan, and the United States—look upon themselves as “mothers of the melon,” little realizing that the real parent is Africa. Few Americans, Australians, Chinese, Russians, Italians, or Iranians realize that the cantaloupe, muskmelon, or Persian melons on their plates originated from wild (and often impossibly bitter) fruits of Africa’s drylands. Like ourselves, melon is African in ultimate origin. Quite a few species of its genus, Cucumis, occur across the continent, and the wild plants that gave rise to today’s melon are native in subSaharan eastern tropical Africa. Probably, it was domesticated after other major crops but, when it left Africa, widely different forms quickly arose in various corners of the world. The crop succeeded first in the drier, longer-season parts of ancient Persia, India, and Southwest Asia (including Egypt); in fact it naturalized in India, which is regarded as a secondary region of novel germplasm. From “Persia” it spread East and West, including all the historic Mediterranean world. It captured the French imagination after reaching there about the fifteenth century; one intellectual produced a treatise enumerating fifty different ways to eat melons, including in soup, fried, or served simply with salt and pepper. The English aristocracy prided itself on the perfect melons their gardeners produced in glasshouses. From Europe, the melon journeyed on westward to the colonies of the Americas. Melons are reasonably priced and seasonably available across countries that span many climatic zones, such as Russia and the US. While lacking a long shelf life, many varieties are tough enough to ship long distances at cool temperatures. Although most people consider it a sugary nothing in nutritional terms, it can be an important source of some nutrients, especially provitamin A.1 Combined with its welter of flavors, textures, sizes, and colors, melon is one of the most promising fruits for further development. Despite its international success, however, the crop is far from being exploited to its fullest, even in the areas that know it best. Indeed, today’s 1 One contributor did write, “Let’s face it, melons are eaten for their taste and sweetness, not nutritional quality. Let’s enjoy it for what it is and be happy we have such a luxury.”
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Lost Crops of Africa: Fruits, Volume III Melons are high-value products in some parts of the world. Shown here is a small specimen in a Nakatsugawa, Japan supermarket, priced (in 2006) at US$25, next to a $15 apple. In most places, melons are more reasonably priced and are seasonally abundant. High in provitamin A, many have rinds robust enough to handle long distance travel. The scope and complexity of flavors, sizes, flesh colors and textures makes the melon one of the most interesting of all fruits. (Karen Rei Pease) melons are based on seed carried out of Africa centuries ago (probably by camel caravans moving across the Sahara to Pharaonic Egypt). The true wealth of its diversity was not only left behind, it remains untapped and unappreciated; at least part of it almost certainly remains undiscovered. This wealth of genetic diversity results from the fact that the melon is perhaps the most horticulturally plastic of all fruits. Few others, if any, can match the range of extreme types that have already been selected. Consider the following range of fascinating features: Size Some melons found in different parts of the world can weigh as much as 30 kg, so large a normal person can hardly lift one; others are no larger than small plums. A type in Australia is the size of a grape. Shape Many melons are not round. One, for example, is about 3 cm in diameter and a meter long, coiling in all directions like a spastic snake. An Algerian type splits into sections, like a half-opened tulip blossom. Color Melons can span at least half the colors of the rainbow: there are types with skins that are red, green, yellow, or mottled; and types with flesh that is red, orange, green, yellow, or white.
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Lost Crops of Africa: Fruits, Volume III Eating Quality Most melons have thin skins and a delicious, melting, honey-like flesh, but some have little or no sweetness at all. Certain ones are hard to distinguish from cucumbers and are eaten as vegetables. One is actually sold under the name “Armenian cucumber.” Other Uses Some melons are grown exclusively for their large, oily seeds, which are roasted like nuts and eaten as snacks. For centuries, “senat” seed was a major export of the Sudan (for more on seeds from various melons, see the Egusi chapter in the companion volume on Africa’s vegetables). In Africa, oil is still often extracted from the seeds of the agrestis subspecies and used as cooking oil. A number of melon types are used as leafy vegetables, boiled and eaten like spinach. Nonfood Uses Some melons are inedible. A few are valued solely for their sweet fragrance, and are used as natural air fresheners. With all these different genetic versions, melons are “designer fruits” par excellence. The possible combinations of shapes and sizes, tastes and textures, colors, and culinary qualities that might be fashioned out of this single species seemingly approaches the infinite. Undoubtedly, some of tomorrow’s most useful melons have yet to be created. These include types especially suited to African conditions, with qualities such as higher nutrition, more rugged exteriors, longer storage times, greater resistance to pest or plague, greater water-thriftiness or heat tolerance, or any of numerous other desirable genetic characteristics that have already been discovered in this amazingly polymorphic plant. Even with the limited germplasm on hand, taxonomists have divided the species into at least eight groups, also considered as subspecies.2 These are: Cantaloupensis—the cantaloupe (as defined in Europe); Reticulatus—the netted or nutmeg muskmelon; cantaloupe (as defined in the United States); Inodorus—winter, honeydew, casaba, or Persian melon; Flexucus—snake or serpent melon; Conomon—Oriental pickling melon; Chito—mango melon, garden melon; Dudaim—pomegranate melon, Queen Anne’s pocket melon; Agrestis—a form grown for its seeds. It seems probable that once Africa’s native melon resources are fully plumbed, this list may have to be revised or expanded, perhaps extensively. 2 These forms are not the type of variety (cultivar) that represents horticultural selections; they are types found in nature and that are differentiated botanically.
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Lost Crops of Africa: Fruits, Volume III PROSPECTS Melons are already more popular than most people think. In the U.S., for instance, they are second only to bananas as the most consumed fresh fruit per person. Despite this, though, the melon has a far greater future ahead. Africa’s raw genetic resources include many remarkable melons, and dozens of new versions of this well-loved worldwide food are likely to be developed. For another, there are also possibilities for greatly increasing local use in dozens of nations. These robust plants not only adapt well to many different situations, they are fast growing, quick maturing, and extremely tolerant of heat, drought, rains, and other climatic stresses. By and large, melons transport well; a few having six-month shelf lives. Indeed, there is already a growing international trade in melons—some of it by air— and this also seems likely to increase. Within Africa For Africa, both the undeveloped local types and the foreign highly developed types have much promise. Humid Areas Moderate to excellent prospects. In spite of the fact that the melon is now a warm-temperate or subtropical crop, it has potential for the monsoonal lowland tropics.3 However, it is susceptible to serious fungal diseases (such as Fusarium), and it generally does best if grown in the drier seasons when heat and humidity are more reasonable. Dry Areas Excellent prospects. Melons probably have their greatest prospects in the drier regions. Most require plenty of sunshine and do well in the hot, dry season. For all that, however, they require plentiful water for the best yields of large fruits. Thus, in truly arid areas they must usually be given at least supplemental irrigation. Upland Areas Fair prospects. This seems to be low elevation crop. Near the equator, however it can be grown at moderate altitude. Beyond Africa Although Africa is the melon’s center of origin, a secondary region of diversity occurs in Asia—specifically in the region covering Iran, the entire Central Asia area,4 India, and parts of China.5 The former Soviet Union, 3 In Indonesia, for example, it is commonly cultivated, especially in East Java and along the northern coast of Java. 4 Ono of our contributors, Henry Shands, emphasized that all Central Asia has great melons: “I have screened melons from Uzbekistan, Turkmenistan, and Kazakhstan and they all have extensive and impressive amounts of genetic variation in size, shape, taste, sugar, etc.”
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Lost Crops of Africa: Fruits, Volume III alone, had more than 1,000 named melons, and Turkey has hundreds…each said to have a distinct flavor. Perhaps nowhere has this fruit’s genetic potential been expressed to a greater degree than in Japan, where melons with elegant shapes and individual aromas sell at astronomical prices and are considered among the most desirable and delectable taste treats. USES Melon has many more uses than most people imagine. Consider, for instance, the following. Fresh Fruits Melons are mostly eaten fresh. The flesh is consumed directly from the rind, occasionally with a little salt, sugar, or maybe powdered ginger. Many Westerners may consume them mainly for breakfast, but in France, they are commonly consumed as an appetizer at the beginning of the evening meal. Most Africans and many others eat them fresh anytime. Melons are also often sliced and peeled to eat with other foods or diced into salads. The fruit may be canned or boiled down into a syrup or jam. A few types are used only as preserves. Processed Foods Not all melons are eaten fresh. Many are dried into a sweet and tangy form of fruit leather that will store for months or years without deteriorating. In Uganda, for example, ripe melons are crushed, the seeds separated, and the flesh dried in the sun. Later this melon leather is washed and boiled in water until soft, then peanut paste is added. The melon leather also may be cooked with dried fish or meat, to which peanut paste is often added. The resulting fragrant sauce is served with millet bread. In Central Asia, dried melon fruit are also eaten year round. Water Melons (native or cultivated) are an important source of water in certain regions of Africa. Some are grown in the fields just for consumption by farm workers seeking relief from the heat of the day. This happens commonly in central Sudan, for example. Vegetables As noted, a number of melons are grown specifically as vegetables. An example is the conomon or melofon,6 grown in parts of Southeast Asia. Fruits are green with yellow stripes, and much more like cucumbers than cantaloupes. Cooked as a vegetable, they are said to make 5 This is perhaps the place where most of today’s cultivated variants originated. Probably, there was independent domestication for subspecies agrestis and conomon in China, India and Japan, and for subspecies melo in Southwest Asia. 6 Cucumis melo subsp. conomon. In English this is usually known as melofon, Oriental pickling melon, or Chinese white cucumber. In Chinese it is ts’it kwa or vet kwa.
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Lost Crops of Africa: Fruits, Volume III an excellent stir-fry. In France, most of the time, cantaloupe muskmelons are eaten as vegetables. Many old local varieties exist but are now unexploited. Seeds Even the types with inedible fruits have uses. They (as well as many edible types) are grown for their seeds. Beyond being roasted and eaten as snacks, melon seeds yield edible oil. In various parts of Africa this liquid is used for cooking and other purposes; some is even exported to Europe. In past years, for instance, Senegal produced 60,000 kilos of melon oil. In Sudan and Ethiopia it is still commercially important. One type of melon7 grown specifically for edible seed (senat) once was a major export. Rind There are melon types that are grown only for the rind, which is used in pickling and preserves. Other Uses In Cameroon, types with small fruits are cultivated almost exclusively for their edible leaves. The fruits of some cultivars are so bizarre-looking that they are grown for use as household curiosities. The dudaim melon8 of equatorial Africa is particularly unusual. Its fruit is all but inedible and no larger than a lemon. However, it has a strong and very pleasant smell. It will keep a kitchen or even the entire house smelling sweet and fresh for weeks. NUTRITION The edible portion can constitute up to 80 percent of a melon. The flesh contains mostly water (about 90 percent) and carbohydrates (10 percent). The carbohydrate is essentially all sugar. As it grows, the fruit accumulates fructose, glucose, and sucrose.9 Upon ripening, it softens and its fruity, aromatic essences are formed. Melons are excellent sources of provitamin A (beta-carotene)—almost as good as mango, with over 3,000 International Units (170 RAE) per 100 grams fresh edible portion. Not unexpectedly, yellow and orange-fleshed melons are the best sources. As to vitamin C, the type known in the United States as cantaloupe contains about 45 mg and honeydew 32 mg per 100 g edible portion, making them a good source of that vitamin as well. Levels of potassium can also be high but highly variable, averaging about 265 mg per 100 g of fresh flesh. The seeds are good sources of energy and protein. The kernel contains approximately 46 percent oil and 36 percent protein. 7 Usually designated Cucumis melo subsp. agrestis, this type occurs wild in tropical Africa but apparently was not domesticated there; it seems to have came back from Asia. 8 Cucumis melo subsp. dudaim. Also known as pomegranate melon or Queen Anne’s pocket melon. 9 As with many cucurbits, the carbohydrate formed in leaves and translocated to fruit is stachyose, a tetrasaccharide. However, the fruit accumulates neither stachyose nor starch.
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Lost Crops of Africa: Fruits, Volume III Today’s melons are derived from seed carried out of Africa, probably on the backs of camels swaying northward across the Sahara in the time of the pharaohs. Melon has “quickly” become one of the most popular fruits. They are second only to bananas as the most consumed fresh fruit in the United States, for example. Despite this, melon could have a far greater future in the daily life of millions, especially given all the untapped biodiversity still in Africa. (USDA, Scott Bauer) HORTICULTURE Because the cultivation of this crop is so well known we need say little. Melons are propagated by seed, of course. Depending on cultivar and soil conditions, they generally require 85-120 days to go from sowing to harvest. Pollination is by insects. Male flowers open first and are the more numerous of the two. If insect pollinators are too few, hand pollination can improve fruit set. However, hand pollination is very inefficient and cannot compete with a hive of honeybees. Yields vary depending on cultivar, planting density, and location. They can be very high. The nationwide average in the United States is 18 tons per ha. Under irrigation a good harvest is 20 tons per ha; without irrigation (but grown on a trellis), 8 tons per ha can be obtained. Perhaps the champion yielder is the Charentais European-type cantaloupe cultivated under glass, mostly on a trellis using plants that are pruned. Production comes in two waves: 25 tons per ha for the first wave, 10 tons per ha for the second. Yields using high intensity “fertigation” can reach 70 tons per ha. Melons are grown in very diverse cropping systems, including many in which it is cultivated concurrently or in rotation with a variety of vegetable
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Lost Crops of Africa: Fruits, Volume III and field crops. Some are grown as a means for making unused scraps of soil productive. Javanese farmers, for example, sow the seeds on dikes between rice fields as well as in the land left to rest and recover following sugarcane. HARVESTING AND HANDLING Although some melon varieties have excellent shelf lives, most must be handled with skill and care. A few demand special attention because their skins are thin and easily bruised. Once ripe, melons decay quickly and become difficult to handle. Lacking starch reserves, they do not ripen or become sweeter after harvest. For the grower this creates a dilemma, because the later they are picked, the shorter the shelf life but the better the taste. Fresh melons may be stored at cool temperatures. LIMITATIONS Melon is still under-collected in Africa and elsewhere. The unusual types are poorly known, and breeding and planting materials are difficult to get. Many African wild melons are bitter. Some Cucumis species are also toxic, although apparently not C. melo. Melon is often susceptible to soil-borne diseases. Heavy losses are often reported because of a premature collapse of the vines. Major causes are fungi, such as fusarium wilt, powdery mildew, and downy mildew. Numerous insect species can be found on melon plants. Only a few are economically important, but they can be devastating. A major pest is the melon aphid. Others include crickets, cutworms, leafminers, armyworm, loopers, borers, and whitefly—a major and evolving problem. High-intensity production of high quality melons requires assured pollination by honeybees or other pollinators. Though not usually a problem in subsistence or backyard horticulture, in many places beehives are brought in and placed in or around large fields to ensure pollination. This creates logistic difficulties as well as potential conflicts with control of insect pests. NEXT STEPS Research needs of conventional, commercial melons do not concern us here. Beyond the periphery of those pressing problems, however, lie fascinating opportunities that can employ African knowledge and genetic resources to open new horizons for production and use of melons within Africa and without. In this sense, then, there are outstanding opportunities for collaborative research between Africans and scientists worldwide. Genetic Diversity An international effort to collect melon germplasm should be mounted. Emphasis should be on unusual types. Many of those are of course to be found in Africa. However, to assess fully the germplasm available for breeding programs, types grown in other regions also need
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Lost Crops of Africa: Fruits, Volume III collection. Special examples of these are the landraces of subsp. melo (Southwest Asia, Egypt, Arabia, Asia Minor, Russia, and the Central Asian Republics) and of subsp. agrestis (Indian Subcontinent, Southeast and East Asia, tropical Africa), and undomesticated material. Genetic Details One of the mysteries behind this crop is the identity of its wild ancestor. African plants now wild may not be true progenitors. Whether these types originated in that locality or are feral escapes from human control is still an open question. A lot about this worldwide crop could be discovered by the unequivocal identification of wild ancestors and the interrelations of all the various diverse melons now found around the globe. Better knowledge of the genetics of Cucumis species—C. melo varieties in particular—would also boost development of all future melons, conventional or exotic. The situation parallels that with Brassica species, in which genetic details have been exploited to create new and commercially viable vegetables related to cabbage, cauliflower, broccoli, and so forth. Melon is a similarly plastic species and carries the potential for creating types with strikingly different qualities. And a better understanding of the genome will help scout the routes to an even greater future for the crop. Melons for Developing Regions Although many improved cultivars have been developed in the United States and other temperate regions, little or no work has been done on improvement of melons for the rigors of field conditions in most developing countries. Plants could be selected whose fruit have less water and more nutritional components, adaptation to tropical climatic and pest conditions, and better fit with local tastes and traditions. Root Fuel The roots of some cucurbits, especially buffalo gourd (Cucurbita foetidissima), are dug and used as “firewood.” The possibility of turning melon roots to this end should also be assessed, especially in areas where fuels are in short supply. Nutritional Improvement There is insufficient work on melon’s overall nutritional qualities. A complete assessment of variation in the divergent types is needed. Also, there is great potential for improving nutrient levels through plant selection or breeding. The levels of both vitamins A and C, for example, can likely be increased with targeted research and the selection of individual plants with high levels of these important nutrients. However, the current ones are already good, and programs to take better advantage of the already available germplasm are very much needed also. Melon Breeding Objectives of melon-breeding programs could be manifold, but might include targets such as improved disease resistance, smaller fruits, better pest resistance, or increased drought tolerance. With
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Lost Crops of Africa: Fruits, Volume III proper research many types of melons can be developed with improved storage qualities. Micropropagation could be used in conjunction with such a breeding program to speed the mass-propagation of rare types. SPECIES INFORMATION Botanical Name Cucumis melo L. Family Cucurbitaceae Common Names China: heung kwa, t’im kwa Dutch: Meloen English: cantaloupe, muskmelon, sweet melon, honeydew melon Ethiopia: yek’ura-haresa (Am) French: cantaloupe, melon German: Melone India: kharlruz, karbuja Indonesia: blewah Kenya: mageye (Swa?) malange (name also used for pumpkin) Malawi: kayimbe (Ch), mpombe (Y), luwimbe (Ng) Malay: blewek Philippines: katimon Spanish: melón South Africa: spanspek Sudan: agur, ajur, fagus, senat-tibish, shammam (Ar) Tanzania: mageye Thai: ma-teng-lai Uganda: akobokobo, akolil (Ts), olujo (Bar), kuluji (Rl) Zambia: mankolobwe, shikaka, vitanguz (wild cucumbers) Zimbabwe: spanspek Description Melons are annuals with climbing, or trailing vines up to 3 m long. The leaves are usually shallow lobed and more or less rounded. The plants are either monoecious (male and female flowers on the same plant) or andromonoecious (male and hermaphroditic flowers on the same plant). Flowers are fragrant, edible, and usually large. Most are yellow; some white. As noted, the fruits are extremely variable. They may be ellipsoid to globose, with or without longitudinal grooves. The skin may be soft or hard, yellow, green, cream, or orange in color; and plain, netted, or prickly in texture. The flesh varies from white to cream-yellow, orange, or green. Most of today’s commercial types have thin skin and thick orange pulp.
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Lost Crops of Africa: Fruits, Volume III Honeydew is an exception. Most melons are many seeded. The seeds are flattened, and may be cream or light yellow. Distribution Melon is grown worldwide. Its exact origin is unknown, but the wild species of Cucumis occur in Africa, so it seems clear that it originated there. Melon’s primary diversity seems to be tropical and subtropical West Africa, where at least 40 Cucumis species are endemic. Many other wild and semicultivated types are found throughout Africa. So too are cultivated types, many of them returnees from Asia, Europe, or the Americas. Although the melon was introduced into Asia at a comparatively late date, well-developed secondary regions of variation now occur in India, China, Iran, and Central Asia. Horticultural Varieties The classification of this highly polymorphic species is confused. A number of species and varieties have been erected from time to time, but this may not be justified as all the forms hybridize readily and there are many intermediate types.10 The most commonly cultivated types are: Cantaloupe melon of Europe (Cantaloupensis group). This has a thick, scaly, rough rind, often deeply grooved. Muskmelon (Reticulatus; called cantaloupe in the trade), grown mainly in the United States. This has smaller fruits and rinds that are finely netted to nearly smooth, with very shallow ribs. Casaba, Persian, or winter melon. Produces large fruits that mature late with good storage quality. The rind is usually smooth, yellow, and often striped or splashed in green and white. The flesh is firm with little musky odor or flavor. The Honeydew cultivar group, America’s best-known winter melons, with ivory skin and green flesh, is of the Inodorus type. Vegetable types. As noted earlier, a number of forms, often with elongate fruits resembling cucumbers, are grown in India and the Far East and used as vegetables. These are mostly domesticates of subspecies agrestis, and were used in Egypt, Palestine, and throughout the Fertile Crescent from ancient times until about 50 years ago.11 In recent times they have attracted research attention in Israel and the United States. 10 One author put it: “Melons are the despair of taxonomists. The exaggerated friendliness of melons makes it difficult for taxonomists to arrange them in categories with any degree of fixity, but they have bravely tried all the same, though sometimes a new variety has to be assigned to one category or the other more or less by guess and by golly.” 11 A contributor commented on this: “There was an attempt at the University of Arizona to develop a muskmelon for use like cucumbers. I have seed and am evaluating them now. The first crop looked promising. Pickles made from these were excellent. They seemed to be crisper than cucumbers.”
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Lost Crops of Africa: Fruits, Volume III Environmental Requirements Melons tolerate a wide range of environmental conditions but require relatively high temperatures—higher than those needed by cucumbers. Optimum growth is obtained during dry periods with high temperatures, moderate humidity, and little diurnal variation. Large fruited types produce well only if supplied with reasonable water and soils. Rainfall Usually rainfall of more than 500 mm is required. It should be well distributed during the period of fruit formation. As noted, under humid conditions melons are prone to leaf diseases. In addition, flowering is reduced and fruit quality is affected. Altitude Elevations below 500 m seem to favor best growth and development, and the conventional types are usually found below about 300 m, even in the tropics. However, melons grow well at 1,500 m in South Africa. In temperate areas, at least, the crop seems restricted by temperature and the length of the growing season rather than by altitude. Certain special types are grown at higher altitudes. For instance, subspecies agrestis thrives at altitudes up to 1,100 m in Ethiopia. Low Temperature The plants are killed by frost. High Temperature Full exposure to the sun is beneficial; melon plants require plenty of sunshine and heat. Optimum growth is obtained in dry periods with temperatures above 24°C. Although much higher temperatures are tolerated, some fruits (winter melon, for example) often need protection from sunburn. (Dry plant material can be used as a cover.) Soil Melons produce best on deep, fertile, neutral to slightly alkaline, well-drained soil. The plant is sensitive to acidity. It can grow well on soils poor in nutrients, but prefers light soils well supplied with organic material with a good moisture-retaining capacity. The root system is sensitive to direct exposure to sun. Daylength For the most part there is no daylength problem in melons, although some cultivars from China and some breeding lines do not set well under shorter daylengths. Salinity Two salt-tolerant cultivars have been developed in Israel. Both have good fruit quality, appearance, and taste and can be irrigated with moderately saline water or survive in salty soils.12 The tang of the salt reportedly enhances the flavor by increasing the percent sugar of the fruit. 12 S. Mendlinger, D. Pasternak, and Y. De Malach, Ramat Negev Experimental Station, Ben-Gurion University of the Negev.
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Lost Crops of Africa: Fruits, Volume III Related Species Cucumis is a genus of about 25-35 species, mostly African. They include the fruit we call cucumber (C. sativus). Among other African types worth exploring as fruits are C. metulifer (the horned melon, see Chapter 5), and C. anguria (both cultivars of the West Indian gherkin and wild types).