The author of this chapter is H. Mahdeem (Boynton Beach, Florida, USA).
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, Fusaea 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 2400 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. glahra; the control of anthracnosis and seed-boring insects; the control of green leaflhoppers; 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 1000 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, sweetsop, custard apple; Spanish: sarumuyo, anón; Portuguese: ata, pinha) seems to be native to southeastern Mexico, in dry areas and between 0 and 1000 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 seedboring insects, the green leaflhopper, 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 Gefner in Israel and the United States and African Pride in Australia.
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.
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.
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.
Figure 7. Custard apples: A) Annona scleroderma; B) A. diversifolia; C) A. reticulate; D) A. cherimola; E) A. muricata; F) A. squamosa
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 1000 and 1400 mm and very fertile volcanic soils.
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:
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.
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:
Botanical name: Annona reticulata L.
Common names. English: bullock's heart, custard apple, sugar apple; Spanish. anona, anona colorada, anona rosada, corazón; Portuguese: coração de boi; other: cahuex, pox, qualtzapotl, tzumuy
Althosugh it is said that A. reticulata is a native of the Antilles. the presence in Guatemala and Belize of a wild variety, A. reticulata var. primigenia, and also of a very wide variability of cultivars suggests that this zone is the species' area of origin. It has been introduced in other regions of the American tropics and Southeast Asia, without achieving a level of importance comparable to that of A. cherimola or A. squamosa.
Of the causes of A. reticulata's current marginalization, two seem to be the most notable: reproduction by seed, which results in many trees producing much smaller fruit; and the attack of the seed weevil which lays its eggs in the young fruit. When the adult insect develops, it bores tunnels through the flesh, causing mycotic infections and a consequent deterioration of the fruit.
The most attractive aspects of this species are: its pleasant-tasting fruit, which is generally sweet and creamy; the relatively small volume taken up by the skin and seed; and the plant's modest soil requirements.
A. reticulata is a low tree with an open, irregular crown and slender, glabrous leaves which in some varieties are long and narrow, 10 to 20 x 2 to 7 cm, straight and pointed at the apex; and in other varieties wrinkled and up to 10 cm wide. The flowers are generally in groups of three or four, with three long outer petals and three very small inner ones. The fruit is heart-shaped or spherical and 8 to 15 cm in diameter; according to the cultivar, the flesh varies from juicy and very aromatic to hard with a repulsive taste. There is a wide variability in the presence of groups of hard cells that are similar to grains of sand. Both the outside and inside colour varies according to the cultivar.
A. reticulata grows between 0 and 1500 m in the areas of Central America that have alternating seasons, and has spread to South America. However, it is in the former region that the varieties previously classified as species are to be found: primigenia, already mentioned; and lutescens. the yellow custard apple which grows from Mexico to Costa Rica.
In Florida (United States) superior cultivars have been selected. especially from Belize and Guatemala. They differ in the characteristics of their fruit and even in their compatibility with stocks.
A. reticulata is generally propagated by seed, the germination rate of which ranges from low to medium. Grafting is usually done on stock of the same species. The fruit is harvested after its colour changes patterns although in some cultivars this does not occur and ripeness is determined by feel. The skin is very thin and the fruit must therefore be handled carefully. Most fruit is produced for family consumption and it is not commonly found on the markets outside Guatemala. The commercial future of this species depends on two factors: the establishment of grafted trees of high-yielding cultivars with fruit of a high quality and good appearance; and the adoption of control practices such as using protective bags or eradicating seed-boring insects.
Botanical name: Annona scleroderma Saff.
Common names. English: poshte; Spanish. chirimoya, anona del monte; other: cawesh, cahuex, poshté
A. scleroderma is one of the least-known fruit trees of the genus; it is grown mainly in southwestern Guatemala and is notable for the structure of its fruit which, unlike the other cultivated species, has a very tough skin, allowing it to be handled much more easily and making it resistant to insect attack. The fruit may be cut and the flesh removed with a spoon. Its potential value is in its high-quality flesh, hard skin and high yield. It could become an export item and a product for wide local consumption.
However, the height of the tree (which does not facilitate fruit harvesting), the fact that the fruit is attacked by birds and the defoliation caused by wind are an obstacle to exploitation of this species.
A. scleroderma is a tall tree which reaches 15 to 20 m and has tough, lanceolate leaves measuring 10 to 25 x 5 to 8 cm. They are shiny on the upper side, slightly pubescent on the underside and have fragile, 3 cm long petioles. The flowers are greenish yellow, the outer petals have a longitudinal prominence which arises in the small branches or in groups in the old part of the thick branches. The fruit occurs in compact spherical groups, is 5 to 10 cm in diameter and generally falls off when ripe, without a noticeable colour change. The cream-coloured flesh has a bittersweet flavour and a soft texture.
This species apparently grows wild on the Atlantic slope from Campeche to Honduras but is only grown in southwestern Guatemala between 300 and 1000 m on the Pacific slope. In this area. which is called the Bocacosta and has very fertile volcanic soils, there is a short dry season and an annual rainfall of around 4000 mm. The plant fruits between late December and April, with a maximum yield around the beginning of February.
The most visible characteristic of variability is in the fruit's surface. The areoles are generally marked by raised edges which form a hexagon. In some varieties, the edges are reduced to a crisscross of brown lines on a smooth, green surface; in other varieties, there is a central prominence on each areole; in some varieties there are well developed edges and prominences, while still others have an irregular, corrugated surface. The fruit also seems to vary in the thickness of its skin, which is on average 3 mm, but slightly thicker and tougher in the smooth-skinned varieties. The Pacific varieties are green or green with brown spots, while those from the Atlantic side have a thicker, reddish green skin.
No cultivars are known to be established by vegetative propagation. Genetic erosion is evident, since it is a crop with a restricted area in a highly populated region where land is required for building or cultivating coffee. Trees which were sown on coffee plantations have been destroyed or deformed because they produce too much shade or because they were damaged by children picking their fruit.
Genetic erosion is very pronounced in A. scleroderma; there are no gene banks and a few plants have been introduced into Australia and the United States ( Florida). For this reason, material urgently needs to be collected in southwestern Guatemala (from San Felipe, San Andrés Villa Seca, San Sebastián, Colomba, El Tumbador, etc.).
Fresh seeds take about a month to germinate. whether they are collected and dried on the same day or stored in bags for a week or two. They do not need to be soaked or treated in any other way. Seeds that have been stored for two to three months need about six months to germinate. In Australia, A. scleroderma grows well when grafted on to stocks of A. muricata and Rollinia mucosa. When grafted material is planted. it must be borne in mind that the trees should be pruned so that a wide crown remains to facilitate fruit harvesting. This also reduces exposure to wind and bird damage.
The shade requirements of young plantsshade seems to promote growthneed to be studied. However, trees located in sunny positions would have a lower, more compact habit. Trees grown from seed begin to produce at around tour years when they reach a height of 4 to 6 m.
The advantages of A. scleroderma as a fruit for local consumption and export are its high productivity and the fact that the flavour and aroma of its flesh are not as strong as in other Annona species, but are different and pleasant. The abundant, cream-coloured or creamy grey flesh separates easily from the seeds and it does not have sandy grains or fibres that adhere to the seed membrane. The thick, leathery skin does not split and is very resistant to insect attack and ordinary packaging and transport.
Activities that merit close attention regarding A. scleroderma are: