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Guava is a genus of tropical shrubs and small trees in the myrtle family Myrtaceae, which has more than 80 genera and 3,000 species. It is a native to the Caribbean, Central America and northern South America, distributed throughout the tropics and subtropics, mostly in the Americas, Asia and Australia (Nakasone and Paull, 1998). It is one of the most gregarious of fruit trees, is almost universally known by its common English name or its equivalent in other languages. In Malaysia, it is generally known either as guava or jambu batu, but has also numerous dialectal names as it does in India, tropical Africa and the Philippines. Various tribal names such as, pichi, posh, enandi, etc. - are employed among the Indians of Mexico and Central and South America.The fruit is edible, round to pear-shaped, from 3-12 cm in diameter. It has a thin delicate rind, pale green to yellow at maturity in some species, pink to red in others, a creamy white or orange-salmon flesh with many small hard seeds, and a strong, characteristic aroma. It is rich in vitamins A, B, and C.

Kingdom	:	Viridiplantae
Phylum	:	Spermatophyta
Subphylum	:	Angiospermae
Class	:	Dicotyledonae
Subclass	:	Rosidae
Order	:	Myrtales
Family	:	Myrtaceae
Subfamily	:	Myrtoideae
Tribe	:	Myrteae
Genus	:	Psidium
Species	:	*guajava*

Psidium guajava is the most important fruit of the myrtle family Myrtaceae. Guava (from Spanish Guayaba; Goiaba in Portuguese) is a genus of about 150 related species of tropical shrubs and small trees in the native to the American tropics and subtropics. Previously the species were divided into Psidium pyriferum and Psidium pomiferum. They are now considered to be the pear-shaped and round varieties of P. guajava. They represent two of the many variations which occur in this species. The pear-shaped forms are often called pear-guava, and the round ones apple-guava. A large white-fleshed kind was formerly sold by Florida nurserymen under the name Psidium guineense, and in California as P. guianense ; but it is now known to be a horticultural form of P. guajava , as is also a round, red-fleshed variety introduced into California under the name P. aromaticum. The true P. guineense, Sw has been itself confused with P. guajava, but can be distinguished from it by its branchlets, which are compressed-cylindrical in place of quadrangular, and by the number of the transverse veins, which is less than in the latter-named species. Today, a wide range of cultivars has been developed in various guava-growing countries (Lim and Khoo, 1990) which includes some of the following:

Psidium littorale [Cattley Guava, Peruvian Guava, "araza" (Colombia), "Chinese guava" (as invasive species)]

Psidium sartorianum [Sartre Guava,"arrayan" (Mexico), guyabita del Peru (Panama, Costa Rica), cambui (Brazil)]

Psidium friedrichsthalium (O. Berg) Mendenza [Cas Guava, Costa Rica Guava, "arrayan" n (El Salvador)]

Psidium littorale Raddi var. littorale [Yellow strawberry guava/Lemon Guava, waiawi (Hawaii)]

The guava is in the Myrtle family (Myrtaceae), which can be easily identified by flowers with long conspicuous stamens and yellow anthers. The guava fruit is a berry with thick pericarp and fleshy seed cavity. The fruits are soft when ripe, making postharvest handling difficult and critical. Poor handling of the ripe fruit can result in great losses in the field and factory. When these ripened fruits are further allowed to be exposed to the hot sun, the guava flesh becomes very soft and mushy. These fruits become difficult to puree in this condition, possibly due to actual chemical breakdown in the tissue.

The flesh color of the fruit is becoming increasing important since the use of coloring dyes in food products is being restricted. Flesh color of wild guavas ranges from white to yellow, salmon-orange and pink, all of which blends into an unattractive yellow-orange product. Wild guava fruits need to be blended with the pink types to produce nectars with acceptable color. Decayed and damaged fruits are discarded before processing.

Tree: Guava trees are evergreen. Generally they grow in a symmetrical dome-shaped and form aborescent shrubs or small trees shallow-rooted, which attain a height of 3 to 6 m with spreading branches. The bark is smooth, mottled green or reddish brown and peels off in thin flakes to reveal the attractive "bony" aspect of its trunk. The plant branches close to the ground and often produces suckers from roots near the base of the trunk. Young twigs are quadrangular and downy. It responds well to controls in many stages of growth and development. Guava is a tree fruit that is well adapted to human manipulation and to changes in orchard management systems.

Leaves: Guava leaves are opposite, short-petioled, oval or oblong-elliptic, somewhat irregular in outline, 5-15 cm long and 2.5-5.1 cm wide acute to rounded at the apex. The dull-green, stiff but leathery leaves with the venation conspicuously impressed on the upper surface, finely pubescent below are slightly downy on the underside. Crushed leaves are aromatic.

Flowers: Guavas are primarily self-fruitful, although some strains seem to produce more fruit when cross-pollinated with another variety by the usual pollinating agent Apis sp. Guavas can bloom throughout the year in the tropics and mild-winter areas, but the heaviest bloom occurs with the onset of warm weather in the spring. The flowers are perfect, bisexual and faintly fragrant, 2.5-3.5 cm wide borne singly or in clusters 2-3 together upon a slender peduncle at the leaf axils of the current or preceding growth ( see picture below ). The tubular calyx splits into irregular segments at anthesis exposing 4 or 5 whitish oval petals which are delicate in texture. The calyx splits open on the previous day and the anthers usually dehisce at anthesis shortly before. The petals are quickly shed, leaving a prominent tuft of perhaps 250 white stamens tipped with pale-yellow anthers surrounding a long slender style connected to the stigma. The ovary is inferior with four or five carpels, each containing numerous ovules in axile placentation.

The flowers usually open between 5 AM and 7 AM depending upon the cultivar and morning temperatures. However, the exact bloom time can vary from year to year depending on the weather. These natural peaks can be altered by changing weather conditions or by cultural manipulations.

Fruit: The fruit is edible, ovoid, round to pear-shaped, varies in size from 3-10 cm in diameter (to 12 cm in some selected cultivars) and has four or five protruding floral remnants (sepals) at the apex. It has a thin delicate rind may be rough or smooth, pale green to yellow at maturity in some species, pink to red in others, a creamy white or orange-salmon flesh with a strong characteristic aroma that varies widely among the seedling population. The flesh may be white, pink, yellow, or red. There are low-acid, sweet types, bland types that are low in both sugars and acidity and high-acid types.The sweet, musky odor is pungent and penetrating. Varieties differ widely in flavor and seediness. The better varieties are soft when ripe, creamy in texture with a rind that softens to be fully edible. It is rich in vitamins A, B, and C The quality of the fruit of guavas grown in cooler areas is often disappointing.

Fruit growth follows a simple sigmoid curve and pulp growth parallels total growth. The days from anthesis to harvest can vary from about 120 to over 220 days, depending upon temperature and fruit development. Cultivars also vary in the period to fruit maturity from anthesis, with up to a 60-day difference.

Where labour is available, young fruits destined for the fresh-fruit market are covered with plastic or paper bags or wrapped with newspaper bags to protect from fruit flies. This procedure does not alter the growth rate or final fruit quality (Lam, 1987).

Seeds: The seeds are usually numerous, small and hard but fully edible, yellowish, 3-5 mm long and fully embedded in the pulp of the core in good varieties. Seed count ranges from 112-535.

Pollination: Guavas are primarily self-fruitful, although most produce more fruit when cross-pollinated with another variety. Plants can bloom throughout the year in tropical areas, but the harviest bloom occurs with the onset of warm weather in spring. The exact time can vary from year to year depending on the weather. Because guavas produce flowers on the current season's growth, you can prune to stimulate bloom. The initial fruit set of guava is quite high as much as 80-86% of the flowers set fruit. However, due to severe fruit drop following fruit set, only 34-56% of the fruit reach maturity (Mitra and Bose, 1985).

Guava generally has pollen with high rates of germination (Hirano and Nakasone, 1969b), except in triploid clones. Fruit set in triploid cultivars is good when they are grown together with diploid clones which serve as a pollen source. Fruit set as high as 90% is obtained when 48-hour-old flowers are pollinated. The period of stigma receptivity in cultivar "Beaument" is about 48 hours. Post-fruit set drop occurs as a result of factors other than pollination. Blossom end rot can occasionally cause heavy drops. Some degree of self- and cross - incompatibilty among guava clones has been shown. Some combinations are totally incompatible while reciprocal crosses produce some fruits. Self-pollinated "Beaumont" produces 100% fruit set between 60% and 80% fruit set by cross pollination with other guava cultivars (Ito and Nakasone, 1968). Such incompatibilities are the result of inhibition of pollen tube growth in the style.

Fruit set by growth regulators: Growth regulators have been tried primarily to produce seedless fruit. Indolebutryic acid, p-chlorophenoxyacetic acid and dichlorisobutryate do not reduce fruit drop.Fruit set after treatment with 50 µg/ml GA is greater and the fruit contains fewer seeds and improved quality characteristics, such as higher TSS and ascorbic acid, as well as reduced fruit drop. Fruit obtained by this treatment is larger than fruit from untreated flowers (Shanmugvelu, 1962). The fruit however, shows 6-8 prominent ridges and swelling at the calyx end.

Production: Guava is primarily self-pollinated, although some strains seem to produce more fruit when cross pollinated with another variety. Depending on climate, cultivar and management practices, it takes approximately 4 to 6 months from flower emergence to fruit ripening on trees. Experiments have shown that spraying young guava trees with 25% urea plus a wetting agent will bring them into production early and shorten the harvest period from the usual 15 weeks to 4 weeks.

Guava trees propagated by budding and grafting will normally bear fruit in 1-2 years while trees from seedlings may take 2 -3 years to begin fruiting, but they attain full bearing capacity at the age of 8-10 years. Seedling trees may not produce quality fruit. The best eating quality fruit generally occurs when it ripens during dry conditions.

However, the yield of a guava plant depends on its age, cropping pattern and the cultural practices. A 10 year-old plant yields about 100kg of fruits every year. If both rainy and winter season crops are taken, more yields may be obtained in the rainy season. It has been reported that five-year-old guava trees can produce from 0.15-0.25 tons of fruit per tree (29.65-49.4 tons per hectare from 197-248 trees). Generally, yield in the first year of bearing is low, but it increases rapidly to reach up to 40-50 tons/ha within 4-5 yers after planting. They live 30 to 40 years but productivity declines after the 15th year.

There could be 2 to 3 harvest seasons of ripe fruit in one year when all climatic requirements are met. Fruit set and yield increases with treatment with gibberellic acid (GA) and at 200 ppm will retain 90% of the matured fruit.The fruit produced will be bigger, have less seeds and improved quality characters such as higher TSS and ascorbic acid.

Uses: Guavas are cultivated in many tropical countries for their edible fruits. The fruit is eaten in many ways, whole, sliced with cream, stewed, preserved, and in shortcakes and pies, but is often prepared in a variety of ways as a dessert. In Asia, raw guava is often dipped in salt or prune powder. Boiled guava is also extensively used to make candies, preserves, jellies, jams, marmalades (goiabada), and juices. Commercially it is used to make the well-known guava jelly and many other products. When well made, guava jelly is deep wine-colored, clear, of very firm consistency, and retains something of the pungent musky flavor which characterizes the fresh fruit. In Brazil a thick jam, known as goiabada , is manufactured and sold extensively. A similar product is made in Florida and the West Indies under the name of guava cheese or guava paste.



Guava fruits with seeds embedded in the pulp of the core		Guava Seeds



Leaves		Flower