Papaya (Carica papaya L.) belongs to Caricaceae, a small family of flowering plants which finds usually in tropical regions of Central and South America and Africa. This plant family contains 32 dioecious species, two trioecious species, and one monoecious species. Papaya is the only species in the genus Carica.
Papaya is a short-lived perennial that can survive around 20 years in the wild and can reach 16 to 33 feet in height. Its hollow, herbaceous stem is barely branched with deeply lobed, palmate like leaves spirally arranged. Flowers are clustered in leaf axils.
Leaves are green, large, palmate like and divided in seven deep lobes which are born on long, hollow petioles emerging from the top of the stem. Older leaves die and fall as the tree grows. Older leaves die and fall as the tree grows. Papaya leaves are steamed and eaten in parts of Asia.
Papaya develops white, fragrant flowers with five cream-white to yellow-orange petals which are usually 1 to 2 in (2.5 to 5.1 cm) in length. The surfaces of the stigma are pale green, and the stamens are bright yellow.
Type of flower depends on the variety and environmental temperature. Within varieties, flower type is usually identified by the size and shape. Flower can contain three type of flowers determined by the presence or absence of male organs (functional stamens) or female organs (stigma and ovary): female flower, male flower and hermaphrodite flower.
Female flowers with a round and large base occur in the leaf axil. It has relatively large white petals, a functional ovary with prominent stigma but no stamen. Female flowers must receive pollen which carries by wind or insects in order to produce fruits.(Chia et al. 2001)
Male flowers with thin,long-tube, small petals develop on a branched peduncle (flower stalk). Male flower contains 10 stamens which can produce pollen, and a trace of an aborted pistil but no ovary. (Chia et al. 2001)
Hermaphrodite flowers present both an tiny ovary with an unbranced stigma and pollen-carrying stamens. They are self-pollinating and have a intermediate size compare to the sizes of female and male flowers. They also develop in the axil of leaves like female flowers. (Chia et al. 2001)
Papaya fruit sometimes used to be referred to as a “tree melon.” In Australia it is called Papaw or Paw Paw. Papaya fruits are yellow-green and smooth skinned on the surface with orange-red underneath it. Large amount of black papaya seeds is located in the middle of the fruit. The size and shape of papaya fruit depends on the variety and type of the plant. Hawaiian variety ‘solo’ usually produce pear-shaped fruits by hermaphrodite plant and weigh approximately 12 to 30 oz (340 to 851g) or round-shaped fruits by female plant. Mexican papaya is heavier (weigh around 10 lb). Other papaya varieties produce various shaped fruits, which can weight up to 20 lb (9.1kg).
Three types are identified based on flower type: female, male and hermaphrodite.
Female plants develop female flowers. Female plants need pollen from nearby male or hermaphrodite trees to set fruit or they would usually fail to produce fruits. Unpollinated female plants occasionally set parthenocarpic fruits, lacking seeds. (Chia et al. 2001)
Male plants presents with large number of male flowers born on their long flower stalks (peduncle). Male plants usually do not produce fruits, but under some conditions there might be female expression in the flower so they might set fruits.
Hermaphrodite plants may have male flowers, hermaphrodite flowers, or both, depending on environmental conditions and the time of year. Hot, arid weather may suppress the ovary and produce male flowers which results in occasional seasonal failure of hermaphrodite plants to set fruit. Male flowers on hermaphrodite plant occur on short peduncle.
Location: Papayas like to be warm with both sunshine and reflected
heat, so the hottest place against the house where nothing else seems happy
is an ideal location. They also like to be as free from wind as possible,
although this is not as critical as their need for sun. Papayas can be grown
successfully in shade, but the fruit is rarely sweet. They are best planted
in mounds or against the foundation of a building where water can be
Soils: Papayas need a light, well-drained soil. They are easily killed by excess moisture. The soil needs to be moist in hot weather and dry in cold weather. Since this is the opposite of California's rain pattern, in addition to good drainage, plastic coverings to prevent over-wetting in winter may also be worthwhile. Papayas do not tolerate salty water or soil.
Irrigation: Watering is the most critical aspect in raising papayas. The plants should be kept on to the dry side to avoid root rot, but also need enough water to support their large leaves. In winter the plant prefers to remain as dry as possible. A plant that has been injured by frost is particularly susceptible to root rot.
Fertilization: The fast-growing papaya requires regular applications of nitrogen fertilizers but the exact rates have not been established. Feed monthly and adjust according to the plant's response. They can take fairly hot organic fertilizing such as chicken manure if used with deep irrigation after warm weather has started. Phosphorus deficiency casuses dark green foliage with a reddish-purple discoloration of leaf veins and stalks.
Pruning:Papayas do not need to be pruned, but some growers pinch the seedlings or cut back established plants to encourage multiple trunks.
Frost Protection: Papayas need warmth and a frost-free environment, but can often withstand light freezes with some kind of overhead protection. This can be provided by building a frame around the plants and covering it with bedding, plastic sheeting, etc. when frost threatens. Electric light bulbs can also be used for added warmth. Potted specimens can be moved to a frost-secure area. Prolonged cold, even if it does not freeze, may adversely affect the plants and the fruit. Mexican papayas are more hardy than Hawaiian varieties.
Propagation: Papayas are normally propagated by seed. To start a plant, extract the seeds from ripe papayas and wash them to remove the gelatinous covering. They are then dried, dusted with a fungicide and planted as soon as possible (the seeds loose their viability rapidly in storage). Plant the seeds in warm (80° F), sterile potting mix. Seeds should be planted in sterile soil as young papaya seedlings have a high mortality rate from damping off. Potting soil can be sterilized by mixing 50-50 with vermiculite and placing in an oven at 200° F for one hour. Under ideal conditions the seeds may germinate in about two weeks, but may take three to five weeks. Gibberellic acid can be used to speed up germination in some seasons. Seedlings usually begin flowering 9 - 12 months after they germinate.
Seedling papayas do not transplant well. Plant them in large containers so the seedlings will have to be transplanted only once, when they go into the ground. Transplant carefully, making sure not to damage the root ball. To prevent damping off, drench the potting mix with a fungicide containing benomyl or captan. Set the plants a little high to allow for settling. A plastic mulch will help keep the soil warm and dry in wet winter areas, but remove it as soon as the weather becomes warm. Plant at least three or four plants to insure yourself of having females or plant hermaphroditic plants.
Papaya plants can also be grown from cuttings, which should be hardened off for a few days and then propped up with the tip touching moist, fertile soil until roots form. Semihardwood cuttings planted during the summer root rapidly and should fruit the following year.
Harvest: Papayas are ready to harvest when most of the skin is yellow-green. After several days of ripening at room temperature, they will be almost fully yellow and slightly soft to the touch. Dark green fruit will not ripen properly off the tree, even though it may turn yellow on the outside. Mature fruit can be stored at 45° F for about 3 weeks. Papayas are often sliced and eaten by themselves or served with a myriad of other foods. They can also be cooked to make chutney or various desserts. Green papayas should not be eaten raw because of the latex they contain, although they are frequently boiled and eaten as a vegetable. In the West Indies, young leaves are cooked and eaten like spinach. In India, seeds are sometimes used as an adulterant in whole black pepper.
Papaya fruit contains rich vitamin A and C, protein, carbohydrates, fiber, iron and calcium with rather low calories, 39 in a 100g (3.5 oz) serving compare to banana’s 92 calories. Ripe papaya is usually consumed raw as a breakfast or dessert fruit; it can also be processed and used in a variety of products such as jams, fruit juices, and ice cream. Papaya is also consumed as a dried fruit. Culled fruits can be fed to pigs and cattle. Unripe papaya can be eaten if cooked and is used in many sauces and cuisines around the world. Papaya seeds are also used as an ingredient in salad dressings. In many parts of the world, unripe papaya has been used for centuries by women as a natural contraceptive and to induce abortion. Modern research has confirmed that unripe papaya does indeed work as a natural contraceptive and can induce abortion when eaten in large quantities.
Papaya leaves and flowers
Unripe, green papaya fruit and the leaves of the papaya tree contain an enzyme called papain. Papain is a milky latex which is either sun-dried or oven-dried used as a natural meat tenderizer for thousands of years and today is an ingredient in many commercial meat tenderizers. It can also be used as digestion aid, burning , rash and cutting treatment, tooth-cleaning powders, and other products. Tea made from papaya leaves is consumed as a cure for malaria in some countries. From several research journals, eating papaya flowers can reduce the level of inflammation in the body, build healthy digestion, increase appetite and prevent from oxidative damage.
Papaya ringspot virus (PRSV) is an aphid-transmitted plant virus belonging to the genus Potyvirus, family Potyviridae, with a positive sense RNA genome.There are two main types of this virus that are serologically indistinguishable and are so closely genetically related that they are now considered the same virus species. Type P isolates (PRSV-P) infects papaya and several members of the melon family (Cucurbitaceae). The other type, Type W isolates (PRSV-W) infects only cucurbits such as watermelon, cucumber, and squash and were originally known as Watermelon mosaic virus (Tripathi et al. 2008).
Both pathotypes are distributed worldwide. PRSV-P is found in places where papaya mainly grow (Tripathi et al. 2008).
Virions are filamentous, non-enveloped and flexuous with the length of 760-800nm and the width of 12 nm. Virus particles comprise of 94.5% protein, containing the virus coat protein (CP) with a molecular weight of about 36kDa and 5.5% nucleic acid (Tripathi et al. 2008).
The virus is usually transmitted through aphids in a non-persistent way. But the virus can also be not seed-transmitted (Tripathi et al. 2008).
PRSV has a limited number of hosts which belong to the families Caricaceae, Chenopodiaceae and Cucurbitaceae. Propagation hosts are: Carica papaya, Cucurbita pepo and Cucumis metuliferus cv. accession 2459. Local lesion assay hosts are: Chenopodium quinoa and Chenopodium amaranticolor (Tripathi et al. 2008).
Two transgenic papaya varieties, Rainbow and SunUp, with engineered resistance to PRSV have been commercially planted in Hawaii since 1998. A lot of practices have implanted to manage the disease like transgenic resistance, tolerant cultivar, cross-protection and so on (Tripathi et al. 2008).
Anthracnose and chocolate spot, Colletotrichum gloeosporioides (fruits, petioles)
Phytophthora, Phytophthora palmivora (fruit, stem, roots)
Powdery mildew, Oidium caricae (leaves)
Black spot, Cercospora papayae (fruit)
Damping off, Pythium, Phytophthora, Rhizoctonia (seedlings)
Wet rot, Phomopsis sp. (fruit)
Dry rot, Mycosphaerella sp. (fruit)
Watery fruit rot, Rhizopus stolonifer
Stem-end rot, Botryodiplodia theobromae, Mycosphaerella sp., Rhizopus stolonifer, Phomopsis sp. (mature fruit)
Papaya ring spot virus (formerly referred to as papaya mosaic)
Reniform nematodes, Rotylenchulus reniformis
Root-knot nematodes, Meloidogyne spp.
Stevens leafhopper, Empoasca stevensi
Mediterranean fruit fly, Ceratitis capitata
Melon fly, Bactrocera cucurbitae
Oriental fruit fly, B. dorsalis
Broad mite, Polyphagotarsonemus latus (seedlings, young plants, lower surface of young leaves)
Red and black flat mite, Brevipalpus phoenicis(fruit)
Tuckerellid mites, Tuckerella ornata, T. pavoniformis (trunks of old plants)
Carmine spider mite, Tetranychus cinnabarinus(lower surface of mature leaves)
Citrus red mite, Panonychus citri (upper surface of mature leaves)
Texas citrus mite, Eutetranychus banksi (upper surface of mature leaves)
1. Chia, C. L., M. S. Nishina, and D. O. Evans. 1989. Papaya. Commodity Fact Sheet PA-3(A) Fruit. Hawaii Cooperative Extension Service, CTAHR, University of Hawaii.
2. Neal, Marie C. In Gardens of Hawaii. Hawaii: Bishop Museum Press, 1965.
3. Tipton, Trace V., Kevin M. Yokoyama, Kulavit Wanitprapha, Stuart T. Nakamoto and C. L. Chia. 1990. Papaya Economic Fact Sheet #10. Department of Agricultural and Resource Economics, CTAHR, University of Hawaii.
4. Statistics of Hawaiian Agriculture 1991. Prepared by: Hawaii Agricultural Statistics Service, PO. Box 22159, Honolulu, Hawaii, 96823-2159. December 1992. 105 pages.