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Page 267 Naranjilla (Lulo) For centuries the naranjilla (Solanum quitoense) has been an immensely popular fruit of Colombia and Ecuador. Writers have described it as “the golden fruit of the Andes” and “the nectar of the gods.” Orange-yellow on the outside, 1 the fruits look somewhat like tomatoes on the inside, but their pulp is green. Their juice, considered the best in the region, is used to flavor drinks. 2 In fact, many even prefer it to orange juice. Although little known to the outside world, naranjilla (usually pronounced na-ran-hee-ya in English) appears likely to produce a new taste for the world's tables. It promises to become a new tropical flavor with a potential at least as great as the increasingly popular passionfruit (see page 287). However, producing naranjilla is a scientific challenge; before it can achieve its potential, it needs intensive research. Despite its overwhelming popularity in the northern Andes, it has been given little serious commercial development. In fact, owing to several factors, naranjilla fruits have become scarce and expensive in Ecuadorian and other Andean markets. 3 Through misfortune and lack of funds, efforts to check the devastation of nematode pests have failed so that production in some areas is declining. On the other hand, demand is higher than ever, owing to naranjilla's local popularity and the increasing export of both fresh fruits and canned products. Given attention, problems such as these should be entirely avoidable, but even when such operational difficulties are overcome, naranjilla will still be a challenge to produce. It has little genetic diversity and, consequently, is probably restricted to a narrow range of habitats. It almost certainly requires a cool, moist environment—a type that is of limited occurrence. It may also require a specialized pollinator. 1 Although “naranjilla” is Spanish for “little orange,” the fruit is not a citrus, but is a relative of the tomato and potato. In many areas it is called “lulo,” a pre-Columbian word, possibly of Quechua origin. 2 In the 1760s, the Majorcan missionary Juan de Santa Gertrudis Serra wrote of the naranjilla: “The fruit is very fresh [and diluted] in water with sugar, makes a refreshing drink of which I may say that it is the most delicious that I have tasted in the world.” 3 In the last decade, prices have increased more than tenfold (even accounting for inflation).

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Page 268 Nonetheless, with study, these problems can probably be overcome, or at least mitigated. Then the taste of naranjilla should become known to millions. PROSPECTS The Andes. Although now in decline, the naranjilla could become one of the major horticultural products of the region and an important market crop for small-scale producers. The fruit or juice (canned, frozen, or concentrated) has considerable export potential. 4 What is needed is a coordinated effort to fully understand the crop's status and difficulties. Nematocides and biological controls are currently available to forestall the devastation caused by root-knot nematodes. In addition, at least two closely related species, apparently highly resistant to the root-knot nematode, seem promising as rootstocks. They may also be sources of genetic resistance, for they form fertile hybrids with naranjilla. Other Developing Areas. With the increasing international demand for exotic fruits, this is a budding crop for the uplands of Central America and for other areas of similar climate. Already, naranjilla has been established as a small-scale crop in Panama, Costa Rica, and Guatemala. Both there and in other frost-free, subtropical sites, it promises to become a substantial resource. However, because of the plant's restrictive climatic and agronomic requirements, success will not be achieved easily. Establishing naranjilla in commercial production will require much work and dedication. Industrialized Regions. Naranjilla can provide the basis for a new fruit-drink flavor that could become popular in North America, Japan, Europe, and other such areas. In a test at Cornell University several years ago, blindfolded panelists unfamiliar with the fruit chose naranjilla juice over apple juice by three to one, and a blend of naranjilla and apple juice over apple juice alone by nine to one. In the 1970s, a major U.S. soup manufacturer created a fruit drink based on naranjilla for nationwide sale, but it reluctantly abandoned the project because of problems in producing a large and reliable supply of fruit. 4 Colombia is already exporting small amounts to Central America and the United States.

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Page 269 ~ enlarge ~ Pasto, Colombia. Naranjilla is among the most popular fruits in the northern Andes. (R.E. Schultes) USES The naranjilla is versatile. It can be eaten raw or cooked or used to make juice. It is also cooked in fruit pies and confections, and is used to make jellies, jams, and other preserves. In Venezuela, Panama, Costa Rica, and Guatemala, unstrained pulp is used for toppings on cheesecakes, sponges, ice cream, yoghurt, and fruit salads. The fresh juice is also processed into frozen concentrate and can be fermented to make wine. Despite its versatility, naranjilla is mainly used at present to flavor drinks. In Ecuador and Colombia, naranjilla sorbete is something of a national drink, often served in hotels and restaurants. It is made like lemonade: the freshly extracted juice is beaten with sugar into a foamy liquid that is green, heavy-bodied, and sweet-sour in flavor. (Most tasters express surprise that it is not a blend of several fruits.) Naranjillas are eaten only when fully ripe, at which time they yield to a soft squeeze and their rather leathery skin is bright orange or yellow (though sometimes still marbled with green). On average, they are about the size of golf balls. The slightly acid flavor is more pronounced if the fruit is not completely ripe. However, even some ripe fruits are too acid to be eaten raw, and the pulp must be sweetened to be palatable.

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Page 270 ~ enlarge ~ Naranjilla fruit on a plant growing near Versailles, Colombia. (J. Morton) NUTRITION The naranjilla is rich in vitamins, proteins, and minerals. 5 It is said to contain pepsin, the stomach enzyme that aids digestion of proteins. AGRONOMY The plant is propagated by seeds, cuttings, or grafts onto the rootstock of other species. Seeds germinate freely. Cuttings root easily, especially when parts of older, slightly woody stems are used. Like many members of the Solanaceae, it can also be regenerated in tissue culture from pieces of leaf or stem tissue. The plant grows rapidly. Seedlings begin bearing in 6–12 months; grafted plants mature even faster, flowering at 3–4 months of age and maturing fruits at 6 months. In principle, this perennial could continue bearing for years, but in the Andes and Central America plantings usually succumb to root-knot nematodes after about 4 years. 5 The composition per 100 g edible portion: calories, 23; water, 92.5 g; protein, 0.6 g; fat, 0.1 g; carbohydrates, 5.7 g; fiber, 0.3 g; ash, 0.8 g; calcium, 8 mg; phosphorus, 12 mg; vitamin A, 600 Int. units; thiamine, 0.04 mg; riboflavin, 0.04 mg; niacin, 1.5 mg; ascorbic acid, 25 mg. Information from J. Morton.

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Page 271 ~ enlarge ~ Naranjilla fruits look something like tomatoes, but they have yellow skin and green flesh. Their greenish juice provides one of the culinary delights of Colombia, Ecuador, and Venezuela. (W.H. Hodge) Naranjilla is a “heavy feeder” and responds well to fertilization. Pruning old woody stems at the end of a fruiting cycle results in vigorous regrowth and prevents fruit size from diminishing. Andean farmers mainly grow naranjilla on rainy slopes, where, as long as temperatures remain moderate, fruits are produced year-round. To prevent fungal and bacterial root infections, well-drained soils are imperative. A common practice is to plant naranjilla in openings in the forest or to interplant it with banana, tamarillo (see page 307), or achira (see page 27). The taller plants help protect the naranjilla's brittle branches from wind damage. 6 HARVESTING AND HANDLING The fruits are closely borne in the axils of the leaves on stems and branches. They are easy to pull off by hand and are normally picked when about half ripe—that is, when they have started to color. (They subsequently ripen normally.) The stiff hairs can irritate the skin, so the fruits are handled with gloves until ripe enough for the fuzz to be wiped off with a towel. The picked fruits have a shelf life of up to two weeks without 6 It has been suggested that on a commercial scale, the naranjilla could be interplanted between babaco (see page 257), mandarin orange, passionfruit (on wire lattices), or other crop with the naranjilla's climatic requirements. Suggestion from D. Endt.

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Page 272 refrigeration, making naranjilla an ideal truck crop. Cold storage lengthens the storage period considerably. Yields are high. Individual plants may produce up to 10 kg of fruit a year, and on a per-hectare basis may yield 27 tons of fruit or 47,000 liters of juice. If not handled correctly, much of the flavor can be lost in canning and the juice can turn muddy looking. Proper cooling, storage, and the use of antioxidants are necessary. LIMITATIONS Naranjilla's major problems have already been discussed. They are its climatic restrictions and susceptibility to pests. More information is given below. Adaptability This plant has received little attention from horticultural researchers; its environmental adaptations, therefore, are not well known, but seem to be narrow. It is possible that it needs a long growing season, as well as high humidity. It cannot tolerate frost. Heat and dryness can also cause crop failure. Moreover, there are possible pollination problems. Naranjilla appears to be a short-day plant; pollen abortion occurs when days are long. 7 Pollinators may be absent in locations outside its native range. The effects of shade and altitude are also uncertain. The plant is said to perform poorly under 1,200 m elevation in the Andes. Pests and Diseases As noted, the plant is extremely susceptible to root-knot nematodes (Meloidogyne species). Plantings often fail to reach full fruiting size as a result. The naranjilla also suffers from insect pests; in particular, a wide variety of coleopterans (beetles and weevils) chew the leaves. The plants can succumb to diseases such as bacterial wilt and fungal infections. Root and stem rots can be particularly severe. Viruses, too, can be troublesome. RESEARCH NEEDS Germplasm Collection Replicate germplasm collections should be established in Ecuador, Colombia, Peru, Costa Rica, and other countries. A germplasm collection of 185 samples is already being evaluated at the Instituto Colombiano Agropecuario (ICA) in Colombia. 8 7 Information from J. Soria. 8 Information from L.E. Lopez J.

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Page 273 Nematodes The nematode problem is the major one to be addressed. As a starter, nematologists should determine the varieties of the offending pests. Also, the relation between nematode resistance and temperature should be checked. (Recent research has shown that nematode-resistant tomatoes become susceptible as temperature rises.) Although nematode-killing chemicals can be used to treat the soil, these tend to be toxic and expensive. An alternative approach could be biological control. 9 Screening for strains resistant to nematodes (and viruses) seems promising as well, although development of horticulturally viable types could take years. Alternative approaches include the following: Hybridizing naranjilla with closely related, nematode-resistant species. Hybrids with Solanum hirtum and S. macranthum, for example, have good nematode resistance. Backcrossing these to naranjilla has produced a range of plants that have shown resistance and have borne fairly good fruit. 10 Grafting naranjilla on related plants with nematode-resistant rootstock. When cleft grafted on species such as S. macranthum and S. mammosum, naranjilla plants have survived for about three years and fruited successfully. In tropical Africa, naranjilla has done well when grafted to its nematode-resistant local relative, S. torum. 11 Improving plant vigor by better management. Producing the crop in beds of sterilized soil. Growing a cover crop or rotation crop of plants, such as velvet bean or Indigofera species, that help eliminate nematode infestations. Inducing somaclonal variation in regenerated plants as a way of unmasking inherent nematode resistance that is now hidden. Educating farmers about nematodes and the means of keeping sites free of infestation. (This is important, whatever other approach may be used.) SPECIES INFORMATION Botanical Name Solanum quitoense Lamarck Family Solanaceae (nightshade family) 9 For example, the bacterium Pasteuria penetrans has proved as effective as current nematocides on other crops in Britain. Spores can be produced in vivo on nematodes in roots, without the necessity of sterile production systems. Information from B.R. Kerry. 10 Information from L.E. Lopez J. 11 Both hybridizing and grafting also bestow resistance to root and collar rot. However, further evaluation is needed to ensure that alkaloids in the fruits do not rise to hazardous levels. Information from J. Soria.

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Page 274 Synonyms Solanum hirsutissimum; Solanum angulatum Common Names Quechua: lulo, lulu puscolulu Spanish: naranjilla, naranjillo; naranjilla de Quito, naranjita, lulo, lullo, toronja, tomate chileno (Peru) English: Quito orange, naranjilla, lulo French: naranjille, morelle de Quito, orange de Quito German: Lulo-Frucht Origin. Naranjilla's origin is unknown. Its wild progenitor may yet be discovered—probably in Colombia. It is thought that the plant was domesticated within the last few hundred years, because there is no evidence that it was cultivated in pre-Columbian times. The first records of naranjilla cultivation are from the mid–1600s in Ecuador and Colombia. Traditionally, areas of major cultivation have been the valleys of Pastaza and Yunguillas in Ecuador and the mountain areas of Cauca and Nariño in Colombia. Description. The plant is a perennial, herbaceous shrub, 1–1.5 m high, with stout, spreading, brittle stems. Its dark-green, purple- or white-veined leaves are often more than 30 cm long and, like the stems, are densely pubescent. The pale-lilac flowers are covered with a thick “felt” of light-purple hairs. The spherical, yellow-orange fruit is 3–8 cm in diameter. It has a leathery skin, densely covered with fine, brittle, easily removed, white to brown hairs. Internally, its structure resembles a tomato. The acidulous, yellow-green flesh contains a greenish pulp with numerous seeds and green-colored juice. Horticultural Varieties. On the whole, the species is unusually uniform for a cultivated plant. However, two geographically separated varieties are recognized. Variety quitoense is the common, spineless form found in southern Colombia and Ecuador. Variety septentrionale has spines, is hardier, and grows mainly at altitudes of 1,000–1,900 m in central Colombia and Costa Rica. In the last few years, an apparently new variety has appeared in Quito markets. Although the fruits are smaller than normal, they are rapidly becoming the dominant commercial type. 12 Investigation of this may help open a new era in naranjilla use. Is this a new hybrid? Is it being grown because of greater nematode resistance? Or is the fact that its fruits have few hairs the driving force behind its production? 12 Information from J. Soria.

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Page 275 Environmental Requirements Daylength. As noted, the plant seems to require short days for pollination. However, this is not certain because satisfactory fruit set has been noted in south Florida at any time of year. 13 Rainfall. Naranjilla requires considerable moisture. It is commercially grown in the Andean areas where annual rainfall is 1,500–3,750 mm. The lower moisture limits are uncertain, but even moderately dry conditions check its growth. Altitude. This is not a restriction. Samples have been collected near 2,000 m elevation in Ecuador, and the plant grows near sea level in New Zealand and California. Low Temperature. Below 10°C the plant's growth is severely checked. It is frost sensitive. High Temperature. Above 30°C the plant grows poorly. It does not set fruit in areas with high night temperature—a possible reason why it has failed in some lowland tropical and subtropical areas. Soil Type. In Ecuador, the naranjilla grows best on fertile, well-drained slopes. It requires soils that hold moisture but that drain well enough to avoid waterlogging. It seems particularly sensitive to salt. 14 Related Species. Naranjilla has several relatives that produce desirable fruits and deserve more attention. They could be useful in their own right as well as perhaps for genetically improving naranjilla. 15 Solanum pectinatum This plant, although undomesticated, produces high-quality fruits, almost as good as those of the naranjilla. Compared with the naranjilla, the fruits are slightly smaller, but their hairs rub off more readily, and they taste somewhat sweeter. This is a lowland species, widely distributed from Peru to southern Mexico, and from sea level to 1500 m. Throughout the region, people gather the wild fruits for making juice. It, too, deserves wider appreciation; a little horticultural investigation might produce a new crop as popular as the naranjilla, but suitable for cultivation in areas too warm for naranjilla. Solanum vestissimum Native to Colombia and Venezuela, this is another wild species with pleasantly flavored fruits. It grows at higher altitudes than naranjilla. Known as “lulo de la tierra fria” (naranjilla of the cold lands), toronja, or tumo, it is a small tree that bears fruit about the size of duck eggs. The chief objection is that the fruit's hairs are quite bristly and the juice is difficult to extract. For all that, however, it has an excellent flavor and deserves research attention. 13 Information from J. Morton. 14 Information from L. Davidson. 15 Information in this section is mainly from C. Heiser.