Papaya

Papaya
Papaya tree and fruit, from Koehler's Medicinal-Plants (1887)
Papaya cross section
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Brassicales
Family:	Caricaceae
Genus:	Carica
Species:	C. papaya
Binomial name
Carica papaya L.[1]

Papaya output in 2005, shown as a percentage of the top producer, Brazil (1.7 megatonnes)

The papaya (/pəˈpaɪə/ or US: /pəˈpɑːjə/) (from Carib via Spanish), papaw, (/pəˈpɔː/^[2]) or pawpaw (/ˈpɔːˌpɔː/^[2]) ^[3] is the plant Carica papaya, one of the 22 accepted species in the genus Carica of the family Caricaceae.^[4]

It is native to the tropics of the Americas, perhaps from southern Mexico and neighboring Central America.^[5] It was first cultivated in Mexico several centuries before the emergence of the Mesoamerican classical civilizations.

Description

The papaya is a small, sparsely branched tree, usually with a single stem growing from 5 to 10 m (16 to 33 ft) tall, with spirally arranged leaves confined to the top of the trunk. The lower trunk is conspicuously scarred where leaves and fruit were borne. The leaves are large, 50–70 cm (20–28 in) in diameter, deeply palmately lobed, with seven lobes. All parts of the plant contain latex in articulated laticifers.^[6] Unusually for such large plants, the trees are dioecious. The flowers are 5-parted and highly dimorphic, the male flowers with the stamens fused to the petals. The female flowers have a superior ovary and five contorted petals loosely connected at the base.^[7]:235 Male and female flowers are borne in the leaf axils, the males in multiflowered dichasia, the female flowers is few-flowered dichasia. The flowers are sweet-scented, open at night and are moth-pollinated.^[6] The fruit is a large berry about 15–45 cm (5.9–17.7 in) long and 10–30 cm (3.9–11.8 in) in diameter.^[6]:88 It is ripe when it feels soft (as soft as a ripe avocado or a bit softer) and its skin has attained an amber to orange hue.

Origin and distribution

Papaya is native to Mexico and extends to South America^[6][1][5] and has become naturalized throughout the Caribbean Islands, Florida and several countries of Africa. Additional crops are grown in India, Australia, Malaysia, Indonesia, the Philippines, Thailand and the U.S. state of Hawaii.^[1]

Cultivation and production

Papaya plants grow in three sexes: male, female, hermaphrodite. The male produces only pollen, never fruit. The female will produce small, inedible fruits unless pollinated. The hermaphrodite can self-pollinate since its flowers contain both male stamens and female ovaries. Almost all commercial papaya orchards contain only hermaphrodites.^[8]

Originally from southern Mexico (particularly Chiapas and Veracruz), Central America, and northern South America,^[5] the papaya is now cultivated in most tropical countries. In cultivation, it grows rapidly, fruiting within three years. It is, however, highly frost-sensitive, limiting its production to tropical climates. Temperatures below −2 °C (29 °F) are greatly harmful if not fatal. In Florida and California, growth is generally limited to southern parts of the states. It prefers sandy, well-drained soil, as standing water will kill the plant within 24 hours.^[9]

For cultivation, however, only female plants are used, since they give off a single flower each time, and close to the base of the plant, while the male gives off multiple flowers in long stems, which result in poorer quality fruit.^[5]

Top producers of papayas, 2013

Country/State	Production in millions of tons
India	5.5
Brazil	1.6
Indonesia	0.9
Nigeria	0.8
Mexico	0.8
World	12.4
Source: United Nations Food and Agricultural Organization, FAOSTAT [10]

India and Brazil are the major producers of papaya, together providing 57% of the world total of 12.4 million tons in 2013 (FAOSTAT chart).

Gaining in popularity among tropical fruits worldwide, papaya is now ranked fourth in total tropical fruit production after bananas, oranges, and mango. Global papaya production has grown significantly over the last few years, mainly as a result of increased production in India.^[11] Papaya has become an important agricultural export for developing countries, where export revenues of the fruit provide a livelihood for thousands of people, especially in Asia and Latin America.

Carica papaya was the first transgenic fruit tree to have its genome sequenced.^[12]

Diseases and pests

Viruses

Papaya ringspot virus is a well-known virus within plants in Florida.^[5] The first signs of the virus are yellowing and vein-clearing of younger leaves, as well as mottling yellow leaves. Infected leaves may obtain blisters, roughen or narrow, with blades sticking upwards from the middle of the leaves. The petioles and stems may develop dark green greasy streaks and in time become shorter. The ringspots are circular, C-shaped markings that are darker green than the fruit itself. In the later stages of the virus, the markings may become gray and crusty. Viral infections impact growth and reduce the fruit's quality. One of the biggest effects that viral infections have on papaya is the taste. As of 2010, the only way to protect papaya from this virus is genetic modification.^[13]

The papaya mosaic virus destroys the plant until only a small tuft of leaves are left. The virus affects both the leaves of the plant and the fruit. Leaves show thin, irregular, dark-green lines around the borders and clear areas around the veins. The more severely affected leaves are irregular and linear in shape. The virus can infect the fruit at any stage of its maturity. Fruits as young as 2 weeks old have been spotted with dark-green ringspots about 1 inch in diameter. Rings on the fruit are most likely seen on either the stem end or the blossom end. In the early stages of the ringspots, the rings tend to be many closed circles, but as the disease develops, the rings will increase in diameter consisting of one large ring. The difference between the ringspot and the mosaic viruses is the ripe fruit in the ringspot has mottling of colors and mosaic does not.^[14]

Fungi

The fungus anthracnose is known to specifically attack papaya, especially the mature fruits. The disease starts out small with very few signs, such as water-soaked spots on ripening fruits. The spots become sunken, turn brown or black, and may get bigger. In some of the older spots, the fungus may produce pink spores. The fruit ends up being soft and having an off flavor because the fungus grows into the fruit.^[15]

The fungus powdery mildew occurs as a superficial white presence on the surface of the leaf in which it is easily recognized. Tiny, light yellow spots begin on the lower surfaces of the leaf as the disease starts to make its way. The spots enlarge and white powdery growth appears on the leaves. The infection usually appears at the upper leaf surface as white fungal growth. Powdery mildew is not as severe as other diseases.^[16]

The fungus phytophthora blight causes damping-off, root rot, stem rot, stem girdling, and fruit rot. Damping-off happens in young plants by wilting and death. The spots on established plants start out as white, water-soaked lesions at the fruit and branch scars. These spots enlarge and eventually cause death. The most dangerous feature of the disease is the infection of the fruit which may be toxic to consumers.^[15] The roots can also be severely and rapidly infected, causing the plant to brown and wilt away, collapsing within days.

Pests

The papaya fruit fly is mainly yellow with black marks.^[5] The female papaya fruit fly has a very long, slender abdomen with an extended ovipositor that exceeds the length of its body. The male papaya fruit fly looks like the female with the differences of a hairy abdomen and no ovipositor. Long, slender eggs are laid inside of the fruit by the female papaya fruit fly. The larvae are white and look very much like the regular fruit fly larvae. The female is capable of laying 100 or more eggs, and they are laid during the evening or early morning in groups of ten inside young fruit. They usually hatch within 12 days of being in the fruit where they feed on the seeds and interior parts of the fruit. When the larvae mature (usually 16 days after being hatched) they eat their way out of the fruit, drop to the ground, and pupate just below the soil and emerge within one to two weeks as mature flies. The flesh of the papaya must be ripe for the fly to migrate towards the surface of the fruit because unripe papaya juice is fatal to them. The papaya will turn yellow and drop to the ground if it is infected by the papaya fruit fly.^[15]

The two-spotted spider mite is a 0.5-mm-long brown or orange-red or a green, greenish yellow translucent oval pest. They all have needle-like piercing-sucking mouthparts and feed by piercing the plant tissue with their mouthparts, usually on the underside of the plant. The spider mites spin fine threads of webbing on the host plant, and when they remove the sap, the mesophyll tissue collapses and a small chlorotic spot forms at the feeding sites. The leaves of the papaya fruit turn yellow, gray, or bronze. If the spider mites are not controlled, they can cause the death of the fruit.^[15]

The papaya whitefly lays yellow, oval eggs that appear dusted on the undersides of the leaves. They eat papaya leaves, therefore damaging the fruit. There, the eggs developed into flies in three stages called instars. The first instar has well-developed legs and is the only mobile immature life stage. The crawlers insert their mouthparts in the lower surfaces of the leaf when they find it suitable and usually do not move again in this stage. The next instars are flattened, oval, and scale-like. In the final stage, the pupal whiteflies are more convex, with large, conspicuously red eyes.^[15]

Cultivars

Papayas with yellow flesh

Two kinds of papayas are commonly grown. One has sweet, red or orange flesh, and the other has yellow flesh; in Australia, these are called "red papaya" and "yellow papaw", respectively.^[17] Either kind, picked green, is called a "green papaya".

The large-fruited, red-fleshed 'Maradol', 'Sunrise', and 'Caribbean Red' papayas often sold in U.S. markets are commonly grown in Mexico and Belize.^[5][18]

In 2011, Philippine researchers reported that by hybridizing papaya with Vasconcellea quercifolia, they had developed conventionally bred, nongenetically engineered papaya resistant to PRV.^[19]

Genetically engineered cultivars

Carica papaya was the first transgenic fruit tree to have its genome sequenced.^[12] In response to the papaya ringspot virus (PRV) outbreak in Hawaii, in 1998, genetically altered papaya were approved and brought to market (including 'SunUp' and 'Rainbow' varieties.) Varieties resistant to PRV have some DNA of this virus incorporated into the DNA of the plant.^[20][21] As of 2010, 80% of Hawaiian papaya plants were genetically modified. The modifications were made by University of Hawaii scientists who made the modified seeds available to farmers without charge.^[22][23]

Papaya flower bud cooked as vegetable in Manado cuisine

Nutrition

In a 100 gram serving, papaya fruit provides 43 kilocalories and is a significant source of vitamin C (75% of the Daily Value, DV) and a moderate source of folate (10% DV), but otherwise has negligible content of nutrients (see table).

Culinary uses

The ripe fruit of the papaya is usually eaten raw, without skin or seeds. The unripe green fruit can be eaten cooked, usually in curries, salads, and stews. Green papaya is used in Southeast Asian cooking, both raw and cooked.^[24] In Thai cuisine, papaya is used to make Thai salads such as som tam and Thai curries such as kaeng som when still not fully ripe. In Indonesian cuisine, the unripe green fruits and young leaves are boiled for use as part of lalab salad, while the flower buds are sautéed and stir-fried with chillies and green tomatoes as Minahasan papaya flower vegetable dish. Papayas have a relatively high amount of pectin, which can be used to make jellies. The smell of ripe, fresh papaya flesh can strike some people as unpleasant. In Brazil, the unripe fruits are often used to make sweets or preserves.

The black seeds of the papaya are edible and have a sharp, spicy taste.^[5] They are sometimes ground and used as a substitute for black pepper.

In some parts of Asia, the young leaves of the papaya are steamed and eaten like spinach.

Meat tenderizing

Both green papaya fruit and the tree's latex are rich in papain,^[5] a protease used for tenderizing meat and other proteins, as practiced currently by indigenous Americans and people of the Caribbean region.^[5] It is now included as a component in some powdered meat tenderizers.^[5]

Phytochemicals

Papaya skin, pulp and seeds contain a variety of phytochemicals, including carotenoids and polyphenols,^[25] as well as benzyl isothiocyanates and benzyl glucosinates, with skin and pulp levels that increase during ripening.^[26] Papaya seeds also contain the cyanogenic substance prunasin.^[27]

Traditional medicine

In some parts of the world, papaya leaves are made into tea as a treatment for malaria, but the mechanism is not understood and no treatment method based on these results has been scientifically proven.^[28]

Allergies and side effects

Papaya releases a latex fluid when not ripe, possibly causing irritation and an allergic reaction in some people.^[5]

Consumption of very large amounts of papaya may cause carotenemia, harmless yellowing of soles and palms. A very large dose would need to be consumed; papaya contains about 6% of the level of beta carotene found in carrots (the most common cause of carotenemia).^[29]

Gallery

• 
  Seedlings
• 
  Buds
• 
  Female flowers
• 
  Male flowers
• 
  Leaf
• 
  Mature tree with unripe fruit in Kinshasa
• 
  Unripe fruit
• 
  Ripe fruit
• 
  Octastichous Phyllotaxy of Papaya leaves

See also

• Green papaya salad

References

External links

Wikibooks Cookbook has a recipe/module on Papaya

Wikimedia Commons has media related to: Carica papaya (category)

• California Rare Fruit Growers: Papaya Fruit Facts