Cucurbita ficifolia

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Botanical name: Cucurbita ficifolia
Bouché
Family: Cucurbitaceae
Common names. English: fig leaf squash. Malabar gourd, cidra, sidra; Nahuatl: chilacoyote (Mexico, Guatemala); Spanish: lacoyote (Peru, Bolivia, Argentina), chiverri (Honduras, Costa Rica), victoria (Colombia)

Origin, domestication and distribution

At the end of the last and the beginning of this century, some authors were suggesting an Asiatic origin for Cucurbita ficifolia. Since the middle of this century, the consensus has been that it is of American origin. However, its centre of origin and domestication are still unknown. Some authors have suggested Central America or southern Mexico as places of origin, while others suggest South America, and more specifically the Andes. Biosystematic studies have been unable to support the Mexican origin suggested by the distribution of common names derived from Nahuatl throughout America.

Archaeological vestiges point to a South American origin, since the oldest remains are Peruvian, but biosystematics have not been able to confirm this hypothesis either.

Attempts at obtaining hybrids beyond the first generation with the other tour cultivated species have failed and the few results obtained have required the use of special techniques such as embryo cultivation. These results have been corroborated by other studies which reveal that C. ficifolia shows considerable isoenzymatic and chromosomic differences compared with all the taxa of the genus.

In addition to the foregoing observations, the recent discovery that Peponapis atrata does not appear to be a specific pollinator of C. ficifolia has led to the suggestion that the wild ancestor of this species might have been a still undiscovered species whose habitat could be the eastern region of the Andes. This is why the possibility of using wild (or cultivated) species in future programmes for the genetic improvement of this crop and their use in the improvement of other cultivated species of the genus is still remote. The importance of these programmes lies in the fact that collections have been identified which are resistant or completely immune to the attack of different viruses that severely affect other cultivated species.

The cultivation of C. ficifolia ranges from northern Mexico to Argentina and Chile. Its spread to Europe (France and Portugal, for example) and Asia (India) apparently began in the sixteenth and seventeenth centuries when its fruit reached the Old World from South America and India. Since then, its cultivation has spread to many other parts of the world (Germany, France, Japan and the Philippines).

Uses and nutritional value

The different parts of C. ficifolia plants are put to various food uses throughout its distribution area in America. The unripe fruit is eaten boiled as a vegetable, while the flesh of the ripe fruit is used to prepare sweets and soft or slightly alcoholic drinks. The seeds are also greatly valued and in Chiapas, Mexico, they are used with honey to prepare desserts known as palanquetas.

In some regions of Mexico (and perhaps other countries of the continent), the young stems (or "runner tips") and also the flowers are eaten as a cooked vegetable, while the ripe fruit is used as fodder for domestic animals. The latter is the commonest use in the Old World where this species has been introduced.

The most important nutritional value is found in the seeds which provide a considerable source of protein and oil. As indicated by its white colour, the flesh of the fruit is deficient in beta carotene, and has a moderate quantity of carbohydrates and a low vitamin and mineral content.

Recent research in Chile has shown that some proteolytic enzymes from the flesh of C. ficifolia fruit can be used to treat waste water from the industrial processing of foods derived from fish.This discovery is of great interest because of the reduction in costs that these industries could achieve by using enzymes which would replace those imported at present.

In Japan and Germany, it has been used as a support or rootstock for the winter production of cucumber (Cucumis sativus L.) in greenhouses.

Botanical description

C. ficifolia is a creeping or climbing plant, monoecious, annual although persistent for a certain period, giving the impression of being a short-lived perennial - without swollen reserve roots. It is resistant to low temperatures but not to severe frosts. It is villose to softly pubescent, with some short, sharp spines dispersed over the vegetative parts. It has five vigorous, slightly angular stems and leaves with 5 to 25 cm petioles that are ovate-cordate to suborbicular-cordale, with or without white spots on the surface, and have three to five rounded or obtuse, apiculate lobules, the central one bigger than the lateral ones. They have denticulate margins and three to four ramified tendrils. The flowers are pentamerous, solitary, and axillary. The male flowers are long and pedicellate have a campanulate calyx that is 5 to 10 mm long and almost as wide, 5 to 15 x 1 to 2mm linear sepals and a tubular campanulate corolla that is rather broader towards the base, 6 to 12 cm long and yellow to pale orange. They have three stamens. The female flowers have sturdy peduncles, 3 to 5 cm long, an ovoid to elliptical, multilocular ovary: sepals that are occasionally foliaceous and a corolla that is somewhat larger than that of the male flowers. They are of a thickened style and have three lobate stigmas. The fruit is globose to ovoid-elliptical, with three colour patterns: i) light or dark green, with or without longitudinal white lines or stripes towards the apex; ii) minutely spotted white and green; iii) white, cream or flesh white. The flesh is sweet and the seeds are ovate-elliptical, flattened, 15 to 25 x 7 to 12 mm, and a dark brown to black or creamy white colour.

Ecology and phytogeography

C. ficifolia is grown over a wide distribution area from 1000 to almost 3000 m in practically all the mountain ranges of Latin America. The restriction of cultivation to areas of considerable altitude is a distinctive characteristic of C. ficifolia compared with other cultivated species of the genus, which can generally grow in a wider range of ecological conditions (in the case of C. pepo and C moschata, from 8 to 2 300 m).

Genetic diversity

Limits of genetic stock. In view of the reproductive incompatibility of C. ficifolia with the other species of the genus, it may be said that its genetic stock is limited to itself. However, in other respects this species is much less different than are other cultivated species of the genus, and there are no commercial cultivars. Among its most notable morphological variations are the coloration and size of its fruit and seeds. The scant morphological variation of this species is consistent with that observed in the patterns of isoenzymes studied so tar.

From the agronomic point of view, it is possible to acknowledge the existence of some genetic diversity for C. ficifolia for two reasons:

· it is cultivated in a wide geographic range where conditions are only relatively uniform as regards altitude, but different from the point of view of other local ecological factors;
· it is grown both without distinction both under agricultural systems with high competition (for example, heavy rain maize fields) and under others with less competition or which allow a more intensive cultivation (for example, maize fields cultivated in the dry season on humid ground, vegetable gardens and plots).

However, none of these aspects has so far been evaluated.

Productivity, as regards the number of fruits and the quantity of seeds per fruit, is another aspect which possibly reflects the genetic diversity of the species and which, again, is insufficiently documented. Field observations have revealed that some medium-sized fruits contain 500 or more seeds and that each plant can produce more than 50 fruits.

Germplasm collections. Accessions of C. ficifolia germplasm are the least abundant of all those existing for the cultivated species of Cucurbita. In addition, they are not very representative of its geographical distribution. There are 338 accessions to be found in America's gene banks; these, added to another 82 deposited with institutions of countries outside the continent, make a total of 420. However, many of the accessions are duplicates. which reduces their number by about half.

Cultivation practices

C. ficifolia is a crop grown mainly in traditional heavy rain agricultural systems, which shows that the start of the rainy season corresponds to the sowing time, while harvesting takes place from the end of September (young fruit and flowers for vegetables) to December or January (ripe fruit for seed and flesh). In some regions of Mexico, such as Mixteca Alta in Oaxaca, it has been found that, in addition to being cultivated during the rainy season on heavily rain-fed terrain, this species is also grown during the dry season on more humid ground (valleys or areas where the soil drainage is slightly deficient). In these cases, sowing is carried out in the early months of the year and the crop is harvested from the dry season (April) until that corresponding to summer (May to July). This has made it possible to ensure almost uninterrupted production throughout the year.

The only form of propagation is the sowing of seed, together with one of the traditional crops of this type of agriculture (maize, bean and other species of Cucurbita) or else cultivation in vegetable gardens along with other species or by itself. The ripe fruit is harvested and selected for seed. It can be stored for long periods (18 to 20 months) and it is frequently seen drying on the roofs of farmers' houses.

Bibliography

Andrés, T.C. 1990. Biosystematics, theories on the origin and breeding potential of Cucurbita ficifolia In D.M. Bates, R.W. Robinson & C. Jeffrey, eds. Biology and utilization of the Cucurbitaceae p. 102- 199. Ithaca, N.Y., USA, Cornell University Press.

Azurdia, C.A. & Gonzalez, M. 1986. Informe final del proyecto de recolección de algunos cultivos nativos de Guatemala. Guatemala, University of San Carlos/ICTA/IBPGR.

Bailey, L.H. The domesticated cucurbits. First Paper. Genet. Herb. 2: 23-34.

Bates, D.M., Robinson, R.W. & Jeffrey, C., eds. 1990. Biology and utilization of the Cucurbitaceae . Ithaca, N.Y., USA, Cornell University Press.

Bukasov, S.M. 1981. Las plantas cultivadas en México, Guatemala y Colombia. Turrialba, Costa Rica, GATIE-GTZ. (Spanish translation by J. Leon)

Delgadillo, S.F., Garzon, T.J.A. & Vega, P.A. 1989. Cucurbit viruses in Mexico: a survey. Fitopatologia 7(2): 136-139.

Lira, R. 1990. Estudios taxonómico y ecogeográfico de las Cucurbitáceas de Latino-américa . 1 st biannual report (Jan.-Aug. 1990). Rome, IBPGR.

Lira, R. 1991. Estudios taxonómico y ecogeográphico de las Cucurbitáceas de Latino-américa . 2nd biannual report (Aug. 1990-Jan. 1991). Rome, IBPGR.

Lira, R. 1991. Estudios taxonómico ecogeográphico de las Cucurbitáceas de Latino-américa . 3rd biannual report (Jan.-Aug. 1991). Rome, IBPGR.

Merrick, L.C.1990. Systematics and evolution of a domesticated squash, Cucurbita argyrosperma and its wild and weedy relatives. In D.M. Bates, R.W. Robinson & C. Jeffrey, eds. Biology and utilizations of the Cucurbitaceae . Ithaca, N.Y., USA, Cornell University Press.

Paris, H.S.1989. Historical records, origins and development of the edible cultivar groups of Cucurbita pepo (Cucurbitaceae). Econ. Bat. 43: 423-443.

Whitaker, T.W. & Davis, G.N. 1962. Cucurbits botany, cultivation and utilizations. London, Leonard Hill.

Chayote (Sechium edule)

Botanical name: Sechium edule (Jacq.) Sw.
Family: Cucurbitaceae
Common names. English: chayote, Madeira marrow, vegetable pear; Nahuatl. chayote (Mexico, Nicaragua, Costa Rica, Panama); Spanish: cidrayota (Colombia), gayota (Peru), huisquil, güisquil or uisquil (Mexico [Chiapas], Guatemala, El Salvador), papa del aire, cayota (Argentina); Portuguese. chocho, chuchu, xuxu, machiche, machuchu (Brazil); French christophine, mirliton (Haiti, Guadeloupe, Bermuda, Trinidad and Tobago, United States [Louisiana], french Guyana)

Origin and domestication

Unlike other crops, there is no archaeological evidence to indicate how long S. edule has been cultivated. Its fleshy fruit, which has a single seed with a smooth testa, does not allow it to be preserved and, as far as is known, no pollen grains or other structure of this species have been identified on archaeological sites.

Chroniclers from the time of the conquest record that. in Mexico at least, the chayote has been cultivated since pre-Columbian times. As regards linguistic references, the common names of native origin are concentrated mainly in Mexico and Central America. Exploration records concur in the finding that the widest variation of S. edule under cultivation is found between southern Mexico and Guatemala. The geographical distribution of the wild relatives of S. edule also testifies to the Mesoamerican origin of this crop.

The closest relatives to S. edule are:

· the so-called wild forms of S. edule, the taxonomic positions of which are unresolved since they are distributed in an apparently natural way in the Mexican states of Veracruz, Puebla, Hidalgo. Oaxaca and Chiapas;
· S. compositum, a species restricted to southern Mexico (Chiapas) and Guatemala;
· S. hintonii, a species endemic to Mexico. until recently considered to be extinct and which grows in the states of Mexico and Guerrero and possibly in Jalisco;
· a new species of the Sechium selection which grows in the north of the state of Oaxaca.

From the foregoing it has been possible to corroborate the fact that S. edule is a species which was undoubtedly domesticated within the cultural area of Mesoamerica, and specifically in the region lying between southern Mexico and Guatemala.

Chayote cultivation is widely distributed in Mesoamerica. It was introduced into the Antilles and South America between the eighteenth and nineteenth centuries. The first botanical description mentioning the name Sechium was in fact done in 1756 by P. Brown who referred to plants grown in Jamaica. During this same period, the chayote was introduced into Europe whence it was taken to Africa, Asia and Australia, while its introduction into the United States dates from the late nineteenth century.

Uses and nutritional value

The chayote is used mainly for human consumption. The fruit, stems and young leaves as well as the tuberized portions of the roots are eaten as a vegetable, both alone and plain boiled, and as an ingredient of numerous stews. Because of its softness, the fruit has been used for children's food, juices, sauces and pasta dishes. In Mexico, an attempt has been made to increase the life of the fruit by drying it. The results have been positive and have enabled jams and other sweets to be prepared while also producing dried fruit which can be used as a vegetable after a certain time. Because of their flexibility and strength, the stems have been used in the craft manufacture of baskets and hats. In India, the fruit and roots are not only used as human food but also as fodder.

The edible parts of S. edule have a lower fibre, protein and vitamin content than other plants. However, the calorie and carbohydrate content is high, chiefly in the case of the young stems, root and seed, while the micronutrients and macronutrients supplied by the fruit are adequate. The fruit and particularly the seeds are rich in amino acids such as aspartic acid, glutamic acid, alanine, arginine, cysteine, phenylalanine, glycine, histidine, isoleucine, leucine, methionine (only in the fruit), proline, serine, tyrosine, threonine and valine.

The chayote also has medicinal uses; infusions of the leaves are used to dissolve kidney stones and to assist in the treatment of arteriosclerosis and hypertension; infusions of the fruit are used to alleviate urine retention. The cardiovascular properties of the infusions of leaves have been tested in modern studies, while their great effectiveness in curing kidney diseases has been known since colonial times on the Yucatan peninsula, where these ailments are very common.

Botanical description

S. edule is a perennial, monoecious climber, with thickened roots and slender, branching stems up to 10 m long. Its leaves are on sulcate petioles of 8 to 15 cm in length, they are ovate-cordate to suborbicular, measure 8 to 18 x 9 to 22 cm, are slightly lobate (with three to five angular lobes) and have minutely denticulate margins and three to five divided tendrils.

The flowers are unisexual, normally pentamerous, coaxillary and with ten nectaries in the form of a pore at the base of the calyx. The staminate flowers grow in axillary racemose inflorescences that are 10 to 30 cm long, and the groups of flowers are distributed at intervals along the rachis. The calyx is patteliform and 5 mm wide, the sepals triangular and 3 to 6 mm long, the petals triangular, greenish to greenish-white and measure 4 to 8 x 2 to 3 mm. There are five stamens, and the filaments are fused almost along their total length, forming a thickened column which separates at the apex into three or five short branches. The pistillate flowers are normally on the same axilla as the staminate flowers; they are usually solitary but are occasionally in pairs; the ovary is globose, ovoid or piriform, glabrous, inerm and unilocular; the perianth is as in the staminate flowers but has slightly different dimensions; the styles are fused in a slender column and the nectaries are generally less evident than in the staminate flowers. The fruit is solitary or rarely occurs in pairs; it is viviparous, fleshy and sometimes longitudinally sulcate or crestate; it is of very different shapes and sizes, indumentum, number and type of spines; it is white and yellowish, or pale green to dark green with a pale green to whitish flesh that is bitter in the wild plants and not bitter in the cultivated ones. The seed is ovoid and compressed with a soft and smooth testa.

FIGURE 6 Chayote (Sechium edule)fruit shapes

Ecology and phytogeography

S. edule is grown traditionally in many regions of the world, preferably between 800 and 1 800 m altitude. In many regions there are variants adapted to cultivation at sea level (in Rio de Janeiro and Yucatan); in other regions it occurs above 2000 m (in Bolivia and in the states of Oaxaca and Chihuahua in Mexico). The wild taxa closest to S. edule show a similar distribution of altitudes, since they grow between 50 and 2 100 m. The chayote is cultivated in a more intensive way and for commercial purposes in Costa Rica, Guatemala, the Dominican Republic and Mexico. The range cultivated is minimal and always in accordance with consumer requirements.

The floral biology of S. edule has been studied in detail: there are various patterns in the structure and sexual expression of the staminate and pistillate flowers, which seem to be determined by genetic, environmental and seasonal factors and by the age of the plants.

Pollination is entomogamous. Among the most efficient pollinators are species of native bees of the genus Trigona, chiefly in areas of medium and low altitudes and which are free from pesticides, and the honeybee (Apis mellifera) on commercial plantations where the use of pesticides is very frequent. Secondary pollinators include wasps of the genera Polybia, Synoeca and Parachartegus.

The fruit of S. edule is viviparous, viz. the seeds germinate inside the fruit even when it is still on the plant. This characteristic does not occur in any of the wild species, in which the seeds germinate asynchronically after falling to the ground. A possible explanation for the viviparism of the cultivate species is that the process of domestication may have resulted in suppression of the dormancy mechanisms.

Genetic diversity

Few cultivated species display the great diversity of shapes, sizes, ornamentation, armature, indumentum and colours as those found in the fruit of the S. edule. However, this diversity, which is present in the most varied combinations, has made it difficult to define cultivars. When reference is made to the different types of S. edule, therefore, it is rather in connection with local races or variants. In addition to morphological diversity, variants exist in the fruiting periods. An example of this has been observed in Oaxaca and Chiapas where local variants can yield between one and four harvests a year. This type of variation has also been cited in the case of other regions.

The considerable diversity farmed by traditional growers contrasts with the relative homogeneity observed in fruit produced on commercial plantations. In these cases, the fruit must comply with the quality requirements demanded by the market: piriform, light green, smooth, about 15 cm long and 450 g in weight; with no physical damage or blemishes caused by pathogens; and with a suitable texture and sweet and pleasant flavour.

The wild relatives closest to S. edule are S. compositum and S. hintonii, whose distribution area is in Mexico and Guatemala. Because of a lack of agronomic evaluations, these species have not been used in genetic improvement programmes which are so necessary in the search for sources of disease resistance.

Germplasm collections. The germination characteristics of S. edule seeds do not allow them to be preserved using simple, orthodox methods. This means that the specimens have to be preserved in field collections which require careful handling.

This type of limitation is evidenced by the disappearance of some of the few collections of the genus Sechium. Between 1 988 and 1990, the biggest collection of cultivated S. edule in the world (at CATIE in Turrialba, Costa Rica) as well as other smaller but equally important collections (for example at CIFAP in Celaya, Mexico) were lost. Fortunately, there are still institutions in the world that are endeavouring to preserve this important genetic stock, at least insofar as the variation of the cultivated species is concerned. Thus, in Mexico there is the collection in the hands of the UACH in Veracruz, with around 150 specimens of cultivated types from Puebla, Veracruz, Oaxaca and Chiapas. This is the only collection which currently preserves plants of some of the most important wild relatives of the chayote, such as S. compositum and the wild types of S. edule. Two other institutions caring for collections of S. edule are the Instituto Superior de Ciencias Agropecuarias of Nicaragua (Centro Experimental Campos Azules) and the Centro Nacional de Pesquisas de Hortalizas, EMBRAPA, Brazil.

Cultivation practices

S. edule is grown in the traditional way on family plots and in backyards and vegetable gardens. The viviparous characteristic of its fruit is familiar to peasant farmers, so that fruit selected for consumption is kept - without being allowed to germinate - by a small cut or puncture made in the embryos, while those selected for seed are simply allowed to ripen until it is decided to plant them.

The normal and most effective form of propagation is from seed. The most widespread sowing practice consists of planting one or more whole fruits. However, on some smallholdings the seed is carefully removed and sown in pots or other media that enable it to be handled for subsequent transplantation in the final sowing plot.

In areas of traditional production, the sowing plot is prepared beforehand by making a hollow in the soil that is big enough to allow the roots to attain maximum development. Next to the sowing plots, a frame of wood or other materials is commonly erected so that the plant can grow on it quickly. For the same reasons, sowing is also frequently carried out close to a tree. During the first weeks of development, the amount of care given is relatively high (irrigation, fertilization with animal or chicken manure, etc.), although attention to the root (protection against physical damage and application of organic fertilizers) is considered of great importance throughout the plant's life cycle.

Sowing can be done at any time of the year, although it generally takes place at the beginning of the rainy season. The average length of the plants' productive cycle is three years or, in exceptional cases, eight.

On commercial plantations, sowing is carried out using rooted cuttings or selected seed. The plants are sown on permanent beds with trellises and are laid out at distances that allow the easiest possible harvesting, transport to cold-storage rooms and packaging. On the commercial type of plantations, chemical and foliar fertilizers are generally used as well as herbicides and nematicides. The leading commercial producer and exporter of chayote fruit is Costa Rica, followed by Guatemala, Mexico and the Dominican Republic.

Prospects for improvement

In spite of the fact that the whole of the S. edule plant can be used and with numerous applications (parts of the plant are used for different purposes), in several countries the majority of these uses have not become widespread and ways have not been devised to make them accessible to sectors of the population other than the peasant community.

The most widespread uses at all levels is that of the fruit as a table vegetable and in the preparation of some industrialized foods. Commercial demand requires a morphologically homogeneous production which rules out the possibility of the considerable range of fruit produced under traditional cultivation systems appearing on the market. However, as the standards required for export are very different from those accepted for the product for local consumption, it is not very likely that the usual varieties will be abandoned and that a serious genetic erosion will occur in the species. A plan to intensify and diversify S. edule production would have to include the following projects:

· The establishment of permanent gene banks in several localities of Mesoamerica to maintain varietal diversity, wild populations and related congeners. These collections can be used to evaluate resistance to diseases, type of growth and organoleptic characteristics of the fruit. They will allow growers to be supplied with new sowing material and will be used as a basis for genetic improvement.
· Programmes for selecting varieties with a high root yield or a high production of young stems. Both are popularly accepted consumer items, with a high nutritional value and potential use as a basic material in agroindustries.
· The development of vegetative propagation methods that will provide growers with sowing material at reasonable prices.
· Basic studies on the most important diseases (Ascochyta phaseolorum, Mycovellosiella cucurbiticola, Fusarium oxysporum and complexes of these and other species), particularly those which attack the fruit and which cause 35 to 40 percent of the rejects in commercial production.
· Identification of problems in postharvest handling, packaging and storage during the marketing process.

Bibliography

Cruz-León, A. 1985-86. Chayote o cruzas intergenéticas? Hallazgo y caracteristicas. Rev., Geogr. Agric.,9-10: 100-106.

Cruz-León, A. & Querol-Lipcovich, D. 1985. Catálog de recursos genéticos de chayote (Sechium edule Sw.) en el Centro Regional Universitario Oriente. Chapingo, Mexico, UACH.

Flores, E. 1989. El chayote, Sechium edule Swartz (Cucurbitaceae). Rev Biol. Trop., 37(1): 1-54.

Jeffrey, C. 1978. Further notes on Cucurbitaceae. IV. Some New World taxa. Kew Bull., 33: 347-380.

Lira, R. 1988. Cucurbitaceae de la península de Yucatan: taxonomía y etnobotánica. Instituto Nacional de Investigaciones sobre Recursos Bióticos, Jalapa, Veracruz. (thesis)

Lira, R. 1990. Estudios taxonómico y ecogeográfica de las Cucurbitáceas de Latino-américa 1st biannual report (Jan.-Aug. 1990). Rome, IBPCR.

Lira, R. 1991. Estudios taxonómico y ecogeográfica de las Cucurbitáceas de Latino-américa 2nd biannual report (Aug.1990-Jan. 1991). Rome, IBPGR.

Maffioli A.1981. Recursos genéticos de chayote, Sechium edule (Jacq.) Swartz (Cucurbitaceae). Turrialba, Costa Rica, CATIE-GTZ.

Newstrom, L. 1989. Reproductive biology and evolution of the cultivated chayote Sechium edule: Cucurbitaceae. In G.H. Bock & Y.B. Linhart, eds. Evolutionary ecology of plants, p.491-509. Boulder, Colo., USA, Westview.

Newstrom, L. 1990. Origin and evolution of chayote, Sechium edule. In D.M. Bates, R.W. Robinson & C. Jeffrey, eds. Biology and utilization of the Cucurbitaceae, p. 141-149. Ithaca, N.Y., Cornell University Press.

Custard apples (Annona spp.)

Annona diversifolia
Annona reticulate
Annona scleroderma

There are an estimated 2 200 species of Annonaceae in the world. These include numerous fruit-trees, especially of the genera Annona and Rollinia; the majority of Annona species and all the Rollinia species originate from the New World.

Many of these species were carefully cultivated by indigenous peoples in Mesoamerica, the inter-Andean valleys. the Amazon region and other areas. Other Annonaceous fruits of the New World include species of Asimina, Duguetia. Fusuea and Porcelia. These fruit-trees have a considerable diversity and degree of adaptation to different environments and are valuable material for hybridization, selection and vegetative propagation studies. The high nutritional value of the fruit, its very distinct flavours and aromas and its attractive shapes and colours justify these efforts.

There are three species, Annona cherimola A. muricata and A. squamosa, which are marginal in several regions of tropical America; in other regions, the technology for producing and handling the product has been developed to such a degree that they cannot really be included in this category. The known techniques and selected cultivars can be extended to regions where cultivation is still underdeveloped. Another three,

A. diversifolia A. reticulata and A scleroderma however, have been marginalized in spite of their intrinsic value and potential as fruit-trees.

The fruit of the Annonaceae must not be seen solely as a luxury item for rich consumers, but also as part of the diet of indigenous populations. This fruit is not only special because of its good flavour; it is also highly nutritional. Its food value varies considerably, but most forms have an abundance of carbohydrates, proteins, calcium, phosphorus, iron, thiamine, niacin and riboflavin, while some are rich in magnesium, ascorbic acid and carotene. If they were plentiful and sold at reasonable prices, they would considerably improve the nutrition of many people.

Annona cherimola Miller, the cherimoya, is thought to originate from cold but frost-free valleys of the Andes at an altitude of between 700 and 2 400 m.

Excellent cultivars are known, all produced by vegetative propagation, which are planted on a commercial scale in Spain, Chile, Australia, Israel, the United States (California, Florida) and the island of Madeira. The fruit is sold in the supermarkets of many countries and is highly regarded.

The commercial cultivars include Bay Ott, Chaffey, Dr White, Libby, Nata, Orton and Spain.

In the regions where the cherimoya is still a marginal crop, new methods must be applied: artificial pollination, grafting of superior cultivars either on to stock of the same species or on to stock of A. squamosa or A. glabra; the control of anthracnosis and seed-boring insects; the control of green leafhoppers; and fruit handling and packaging.

A. muricata L. (English: soursop; Spanish: guanábana; Portuguese: graviola) is possibly native to the Antilles and to the northern part of South America. It grows between 0 and 1 000 m altitude. Its commercial production has been developed in Brazil, Venezuela, Costa Rica and other countries for local consumption and export. Cultivation practices have been established in the production areas mentioned; they include the control of insects and diseases and protection of the fruit in plastic bags. There is a great deal of variation in fruit size and sugar content. Trees of higher quality or resistance must be grafted on to stocks of the same species of A. purpurea and A. montana or, with great difficulty, on A. glabra.

A. squamosa L. (English: sugar apple, sweet-sop, custard apple; Spanish: sarumuyo, anón Portuguese; ata, pinha) seems to be native to southeastern Mexico, in dry areas and between 0 and 1 000 m, although it grows well in regions of medium humidity. It has spread throughout the tropics and displays great variability in India. It is propagated by seed with satisfactory results; however, commercial cultivars are grafted. Of these, Red Sugar, with a red skin and white flesh, is recommended. The main problems are seed-boring insects, the green leafhopper, the tendency towards mummification of the fruit and harvesting and packaging difficulties caused by the fruit's lack of firmness.

The name "atemoyas", derived from "ata" (in Portuguese) and "cherimoya", is given to hybrids between these two species. Several cultivars are known which are sown commercially in the United States (Florida) and Australia. The best atemoyas combine adaptation to low altitudes and hot climate and the high productivity and good flavour of A. squamosa with the firm skin, low flesh/seed ratio and the flavour and aroma of A. cherimola so that, from the standpoint of quality and packaging, the product is comparable to the best cherimoyas, although it has a higher sugar content. At present, crosses are being made between cultivars of cherimoya and A. squamosa Red Sugar and M-2, with the aim of obtaining atemoyas with red- or pink-skinned fruit, which is more attractive than the green fruit of those currently available. The most famous green cultivars are Cefner in Israel and the United States and African Pride in Australia.

Annona diversifolia

Botanical name: Annona diversifolia Saff.
Family: Annonaceae
Common names. English: llama; Spanish: anona blanca; other: llama, ilamatzapotl, izlama, papausa

This fruit-tree, which is very highly regarded in its area of origin, has not been developed as it deserves, since it is virtually planted exclusively by indigenous peoples. Although it is greatly esteemed and fetches a good price on the markets of Guatemala, its cultivation does not attract other agricultural owners, nor do the latter obtain bank credit for this tree, whereas they do obtain it for exotic fruit-trees. Other factors that add to its neglect are: the tree's low productivity; the difficulty of seed germination (although methods to encourage germination artificially are already known); and the short shelf-life of the fruit at the markets (two to three days at ambient temperature). If it is left to ripen on the tree, the fruit splits, but if it is picked in this state and stored at normal temperature, the splits scar over. In Guatemala, it is customary to pick the fruit split in this way and to ripen them subsequently in crates or other closed places.

Botanical description

A. diversifolia is distinguished from other species of Annona in that it has two classes of leaf: the usual obovate, glabrous leaves with a petiole; and leaves in the form of round, deciduous bracts without a petiole, which grow on the base of the small branches. The undersides of the leaves, small branches and fruit have a powdery, whitish appearance, which is more noticeable in the white-fleshed varieties.

FIGURE 7 Custard apples: A) Annona scleroderma; B) A. diversifolia; C) A. reticulate; D) A. cherimola;E) A. muricata; F) A. squamosa

The flowers have three outer petals that are 2 to 5 cm long, and three minute inner petals; the colour is a varietal characteristic and ranges from pink to purplish red.

The fruit, which is about 12 cm long, has white, pink or reddish flesh, with a typical aroma and a sweet, exquisite flavour which, according to most people, is superior to that of the cherimoya. The fruit is very resistant and sometimes completely immune to attack from seed-boring insects.

Ecology and phytogeography

The llama grows between 0 and 1800 m on the Pacific slope from central Mexico to El Salvador, but it is sown more intensively between 200 and 600 m in southwestern Guatemala. This region has a pronounced dry season (December to March)' with an annual rainfall of between 1 000 and 1 400 mm and very fertile volcanic soils.

Genetic diversity

A. diversifolia is grown alone in vegetable gardens with few trees, and a wide variability is noted. This is particularly expressed in the characteristics of its fruit: its colour (see list of cultivars); its texture, which can range from slightly pasty to juicy, soft or with concentrations of harder grain; and its sweet taste, with a typical aroma. Following is a list of A. diversifolia cultivars:

· Fairchild, Rosendo Perez, Guillermo and Gramajo have a thick-skinned, greyish green fruit with prominent round areoles and pink flesh. Rosendo Perez and Gramajo have big fruit. (These cultivars have been bred for Florida.)
· Imery (bred in El Salvador) has big fruit that has a thinner skin, low prominences, is pinkish green (greyish brown when ripe) and has pink flesh with bolder spots.
· Pajapita has a soft, pink surface (brown when ripe) and bright-pink flesh.
· Nilito has a slightly irregular surface, which is bluish green, and red flesh.
· Roman has smaller fruit with a hard skin, which is bluish green with pink spots, and purple flesh.
· Genova white has a smooth, thin, whitish green skin, and white flesh.
· Efrain has up to 200 fruits per tree.

Guatemalan markets sell an llama that has bluish green fruit, with swirling marks such as those in a Van Gogh painting, and delicious bright-red flesh which is easily separated from the seeds. The trees from which this fruit comes have not yet been studied.

The only region to be evaluated as regards genetic erosion is southwestern Guatemala, where the problem does not seem to be serious. There are no gene banks, nor are any preservation techniques known other than live collections. The most promising areas for future exploration are southwestern Guatemala and the state of Chiapas in Mexico.

Cultivation practices

The llama is only grown together with other fruit-trees, on the patios of houses or on smallholdings belonging to indigenous peoples. It is always propagated by seed with a long dormancy period which is difficult to interrupt. The seeds should not be sown without being pretreated to interrupt dormancy, such as soaking them in a solution of gibberellic acid, exposing them to the sun, immersing them in hot water or storing them for two to three months.

Prospects for improvement

In the case of A. diversifolia urgent work is needed in the following areas:

· vegetative propagation, by grafting, of the best varieties, using various stocks and grafting methods;
· effective interruption of seed dormancy;
· picking and commercial handling of the fruit;
· increasing the production period (July -August) by selecting early and late varieties;
· the establishment of gene banks, at least in localities of the Pacific area of Central America and Mexico;
· stepping up exploration of the species' production areas in Mexico, Guatemala and El Salvador;
· hybridization with other species of Annona for the production of more adaptable varieties;
· research on stock of the related wild species A. macroprophyllata from Guatemala and El Salvador;
· research into the possibility that the absence of mycorrhizae or other soil factors are responsible for the growth of this species in other regions of Mesoamerica with favourable climate and soils, and into the possible use of grafting in these cases.


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