Annona

Some 169 (see text)

Annona (from Taíno annon) is a genus of flowering plants in the pawpaw/sugar apple family, Annonaceae. It is the second largest genus in the family after Guatteria,[3] containing approximately 166[4] species of mostly Neotropical and Afrotropical trees and shrubs.[5]

The generic name derives from anón, a Hispaniolan Taíno word for the fruit.[6] Paleoethnobotanical studies have dated Annona exploitation and cultivation in the Yautepec River region of Medicoto to approximately 1000 BC.[7] Plants of the genus have several common names, including sugar-apple, soursop, and guanabana.

Currently, seven Annona species and one hybrid are grown for domestic or commercial use, mostly for the edible and nutritious fruits; several others also produce edible fruits.[8] Many of the species are used in traditional medicines for the treatment of a variety of diseases, though their efficacy has yet to be validated scientifically. Several annonacaeous species have been found to contain acetogenins, a class of natural compounds with a wide variety of biological activities.[9][10] The first complete genome for a species in this genus (Annona muricata) was published in 2021.[11]

Annona species are taprooted, evergreen or semideciduous, tropical trees or shrubs.[5] The plants typically grow in areas where air temperature does not drop below 28 °F (−2 °C), especially Cuba, Jamaica, Central America, India the Philippines and Calabria (southern Italy). However, they have also been known to grow in certain parts of the Andes mountains in South America and in Florida.

The woody trunks have thin bark that has broad and shallow depressions or fissures which join together and are scaly, giving rise to slender, stiff, cylindrical, and tapering shoots with raised pores and naked buds.[5] Leaf blades can be leathery or thin and rather soft or pliable, bald or hairy.[5]

The flowering stalks rise from axils, or occasionally from axillary buds on main stems or older stems, or as solitary flowers or small bundles of flowers. Usually, the three or four deciduous sepals are smaller than the outer petals that do not overlap while in bud. Six to eight fleshy petals are arranged in two whorls—the petals of the outer whorl are larger and do not overlap; inner petals are ascending and distinctively smaller, and nectar glands are darker pigmented. The numerous stamens are ball-shaped, club-shaped, or curved and hooded or pointed beyond anther sac. Numerous pistils, attached directly to the base, are partially united to various degrees with a distinct stigma, with one or two ovules per pistil; the style and stigma are club-shaped or narrowly conic.[5]

One fleshy, ovate to spherical fruit is produced per flower. Each fruit consists of many individual small fruits or syncarps, with one syncarp and seed per pistil. Seeds are bean-like with tough coats; the seed kernels are toxic.[5]

Pollination occurs via Dynastid scarab beetles, which appear to be basic generalists within the genus Annona. Those species of Annona which are more morphologically derived, as well as all Rollinia spp., possess reduced floral chambers and attract small beetles such as Nitidulidae or Staphylinidae.[12]

The compound annonacin and dozens of other acetogenins contained in the seeds and fruit of some members of Annonaceae such as Annona muricata (soursop) are neurotoxins and seem to be the cause of a Parkinson-like neurodegenerative disease. The only group of people known to be affected by this disease live on the Caribbean island of Guadeloupe and the problem presumably occurs with the consumption of plants containing annonacin. The disorder is a so-called tauopathy associated with a pathologic accumulation of tau protein in the brain. Experimental results published in 2007 demonstrated for the first time that the plant neurotoxin annonacin is responsible for this accumulation.[13]

There are 169 accepted Annona species, as of April 2021, according to Plants of the World Online.[2]

Annona species are generally disease-free. They are susceptible to some fungi and wilt. Ants may also be a problem, since they promote mealybugs on the fruit.[14]

Atemoya (A. cherimola × A. squamosa)

Cherimoya (A. cherimola) plantation

Soursop (A. muricata)

Sugar apples (A. squamosa)

Sugar Apple (A. squamosa) interior

Sugar apple interior

Sugar apple exterior

Annona muricata

A.crassiflora fruit

The fruit of A. salzmannii

Annona squamosa flower and leaves in Hyderabad, India

Annona glabra fruit.

Annona cherimola fruit, Pedra Bela, Brazil