From Neglected crops: 1492 from a different perspective
by H. Mahdeem (Boyton Beach, Florida, USA)




Annona scleroderma Saff.
Excerpt from Custard Apples (Annona spp.)


Common Names: English: poshte; Spanish. chirimoya, anona del monte; other: cawesh, cahuex, poshté
Family: Annonaceae


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.

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Botanical description
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.


Ecology and phytogeography
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.


Genetic diversity
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.).

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Cultivation practices
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 plants—shade seems to promote growth—need 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.


Prospects for improvement
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:

the collection and evaluation of genetic material; propagation through grafting on to stock of the same species or related species to obtain low trees with an open crown, which facilitate fruit harvesting;

running small market gardens or interplanted crops; marketing, since it is a "new" fruit even for Guatemalan markets;

packaging and transport technology to prolong the good condition of the fruit and its acceptance on the market.

Bibliography

Bermejo, Hernandez J.e. and Leon, J. "Custard Apple (annona spp.)." fao.org. Neglected crops: 1492 from a different perspective. 85-92 by H. Mahdeem. (FAO Plant Production and Protection Series, no.26). Food and Agriculture Organization of the United Nations, Rome, 1994. Web. 13 Feb. 2016.

Published 9 Apr. 2015 LR. Updated 13 Feb. 2016 LR
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