Annona squamosa

Annona squamosa is a small, well-branched tree or shrub from the family Annonaceae that bears edible fruits called sugar apples or sweetsops or custard apples. It tolerates a tropical lowland climate better than its relatives Annona reticulata and Annona cherimola helping make it the most widely cultivated of these species.
Annona squamosa is semi- deciduous, and tall, similar to soursop. It is a native of tropical climate in the Americas, and Spanish traders aboard the Manila galleons docking in the Philippines brought it to Asia.
File:Custard Apple - Flora Sinensis 1656.jpg|thumb|237px|Michał Boym's drawing of, probably, the sugar-apple, in his Flora Sinensis
The fruit is spherical-conical, in diameter and long, and weighing, with a thick rind composed of knobby segments. The colour is typically pale green through blue-green, with a deep pink blush in certain varieties, and typically has a bloom. It is unique among Annona fruits in being segmented; the segments tend to separate when ripe, exposing the innards.
The flesh is fragrant and sweet, creamy white through light yellow, and resembles and tastes like custard. The seeds are coated with the flesh, It is found adhering to seeds forming individual segments arranged in a single layer around a conical core. It is soft, slightly grainy, and slippery. The hard, shiny seeds may number 20–40 or more per fruit and have a brown to black coat, although varieties exist that are almost seedless. The seeds can be ground for use as an insecticide, although this has not been approved by the US EPA or EU authorities. The stems run through the centre of the fruit connecting it to the outside. The skin is shaped like a Reuleaux triangle coloured green and rough in texture. Due to the soft flesh and structure of the sugar apple it is very fragile to pressure when ripe.
New varieties are also being developed in Taiwan and Hong Kong. The atemoya or "pineapple sugar-apple", a hybrid between the sugar-apple and the cherimoya, is popular in Taiwan, although it was first developed in the United States in 1908. The fruit is similar in sweetness to the sugar-apple, but has a very different taste. As its name suggests, it tastes like pineapple.

Description

The fruit of A. squamosa has sweet whitish pulp, and is popular in tropical markets.

Stems and leaves

Branches with light brown bark and visible leaf scars; inner bark light yellow and slightly bitter; twigs become brown with light brown dots.
Thin, simple, alternate leaves occur singly, long and wide; rounded at the base and pointed at the tip. They are pale green on both surfaces and mostly hairless with slight hairs on the underside when young. The sides sometimes are slightly unequal and the leaf edges are without teeth, inconspicuously hairy when young.
The leaf stalks are long, green, and sparsely pubescent.

Flowers

Solitary or in short lateral clusters of 2–4 about long, greenish-yellow flowers on a hairy, slender long stalk. Three green outer petals, purplish at the base, oblong, long, and wide, three inner petals reduced to minute scales or absent. Very numerous stamens; crowded, white, less than long; ovary light green. Styles white, crowded on the raised axis. Each pistil forms a separate tubercle, mostly long and wide which matures into the aggregate fruit.
Flowering occurs in spring-early summer and flowers are pollinated by nitidulid beetles. Its pollen is shed as permanent tetrads.

Fruits and reproduction

Fruits ripen 3 to 4 months after flowering. Aggregate and soft fruits form from the numerous and loosely united pistils of a flower which become enlarged and mature into fruits which are distinct from fruits of other species of genus.
The round or heart-shaped greenish yellow, ripened aggregate fruit is pendulous on a thickened stalk; in diameter with many round protuberances and covered with a powdery bloom. Fruits are formed of loosely cohering or almost free carpels.
The pulp is white tinged yellow, edible and sweetly aromatic. Each carpel containing an oblong, shiny and smooth, dark brown to black, long seed.

Nutrition and uses

Sugar-apple is high in energy, an excellent source of vitamin C and manganese, a good source of thiamine and vitamin B₆, and provides vitamin B₂, B₃ B₅, B₉, iron, magnesium, phosphorus and potassium in fair quantities.

Chemistry

The diterpenoid alkaloid atisine is the most abundant alkaloid in the root. Other constituents of Annona squamosa include the alkaloids oxophoebine, reticuline, isocorydine, and methylcorydaldine, and the flavonoid quercetin-3-O-glucoside.
Bayer AG has patented the extraction process and molecular identity of the annonaceous acetogenin annonin, as well as its use as a biopesticide, although this use has not been approved by US or EU authorities. Other acetogenins have been isolated from the seeds, bark, and leaves.

Distribution and habitat

Annona squamosa is native to the tropical Americas, but the exact origin is unknown. It is now the most widely cultivated of all the species of Annona, being grown for its fruit throughout the tropics and warmer subtropics, such as India, Indonesia, Thailand, Taiwan, and China as far north as Suzhou; it was introduced to southern Asia before 1590. It is naturalized as far north as Cuba, south Florida and as far south as Bahia, Brazil, and is an invasive species in some areas.
;Native range:
;Naturalised range:

Climate and cultivation

Like most species of Annona, it requires a tropical or subtropical climate with summer temperatures from to, and mean winter temperatures above. It is sensitive to cold and frost, being defoliated below and killed by temperatures of a couple of degrees below freezing. It is only moderately drought-tolerant, requiring at least of annual rainfall, and does not produce fruit well during droughts.
It will grow from sea level to an altitude of and thrives in hot dry climates, differing in its tolerance of lowland tropics from many of the other fruit bearers in the Annona family.
It is quite a prolific bearer, and it produces fruit within as little as two to three years. A five-year-old tree can produce as many as 50 sugar apples. Poor fruit production has been reported in Florida because there are few natural pollinators ; however, hand pollination with a natural fibre brush is effective in increasing yield. Natural pollinators include beetles of the families Nitidulidae, Staphylinidae, Chrysomelidae, Curculionidae and Scarabaeidae.

Ecology

It is a host plant for larvae of the butterfly Graphium agamemnon. In the Philippines, the fruit is commonly eaten by the Philippine fruit bat, which spreads the seeds from island to island.

Uses

In traditional Indian, Thai, and Native American medicines, the leaves are boiled down with water, possibly mixed with other specific botanicals, and used in a decoction to treat dysentery and urinary tract infection. In traditional Indian medicine, the leaves are also crushed for use as a poultice, and applied to wounds. In Mexico, the leaves are rubbed on floors and put in hens' nests, to repel lice. Extracts are used in ethnomedicine.
In Haiti, the fruit is known as cachiman and is used to simply make juice.