CHAPTER XX MANGO To Section 2

Organization: Instituto Tecnologico de Veracruz (ITVER)(http://www.itver.edu.mx)
Authors: J. De La Cruz Medina, H.S. García (jdlcruz@itver.edu.mx)
Edited by AGSI/FAO: Danilo Mejia,PhD (Technical), Beverly Lewis (Language & Style),
Beverly Lewis (HTML transfer)

The Mango (Mangifera indica L.) is the most economically important fruit in the Anacardiaceae (Cashew or poison ivy family). Other important members of this family include cashew and pistachio. The mango is the most important foodstuff for inhabitants of the tropics after the banana. There are 150 cultivars of mangoes produced around the world. Producing areas can be grouped in 6 regions (See Figure 1 for Mango producing areas):

· Florida (USA), Mexico, Central America
· West Indies (Caribbean Islands)
· South America
· Africa/Arabian Peninsula
· Indian Subcontinent
· Indochina (China)/Indonesia/Pacific

Figure1. Mango producing areas.

The percentage composition of the typical Tommy Atkins mango is: stone wet (8.5 percent), skin (12 percent) and pulp (79.5 percent) (See Figure 2 for photo of typical Tommy Atkins mangoes and Figure 3 for the percentage composition of the Tommy Atkins mango). The fruits produce either monoembryonic or polyembryonic seeds. Polyembryonic seeds contain more than 1 embryo and most of the embryos are genetically identical to the mother tree. Monoembryonic seeds contain 1 embryo and this embryo possesses genes from both parents (Crane and Campbell, 1999).

Figure 2. Typical Tommy Atkins mango.

Figure 3. Tommy Atkins mango percentage composition.

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a) Origin

Native to southern Asia, specially Eastern India, Burma and the Andaman Islands, mango has been cultivated, praised and even revered in its homeland since ancient times. Buddhist monks are believed to have taken the mango on voyages to Malaya and eastern Asia in the 4th and 5th Centuries BC. Persians are said to have taken mangoes to East Africa around the 10th Century AD. The fruit was grown in the East Indies before the earliest visits of the Portuguese who apparently introduced it to West Africa in the early 16th Century and also into Brazil. After becoming established in Brazil, the mango was carried to the West Indies, being first planted in Barbados about 1742 and later in the Dominican Republic. It reached Jamaica about 1782 and, early in the 19th Century, reached Mexico from the Philippines and the West Indies (Morton, 1987).

Experts at the Birbal Sahni Institute of Palaeobotany (BSIP) here have traced the origin of mango to the hills of Meghalaya, India from a 65 million year-old fossil of a mango leaf. The earlier fossil records of mango (Mangifera indica) from the Northeast and elsewhere were 25 to 30 million years old. The 'carbonized leaf fossil' from Damalgiri area of Meghalaya hills, believed to be a mango tree from the peninsular India, was found by Dr R. C. Mehrotra, senior scientist, BSIP and his colleagues. After careful analysis of the fossil of the mango leaf and leaves of modern plants, the BISP scientist found many of the fossil leaf characters to be similar to mangifera.

An extensive study of the anatomy and morphology of several modern-day species of the genus mangifera with the fossil samples had reinforced the concept that its centre of origin is Northeast India, from where it spread into neighbouring areas, says Dr. Mehrotra. The genus is believed to have disseminated into neighbouring areas after the formation of land connections between India and Malaysia through Burma after the collision of the Indian plate with the Asian plate. After the land connection was established between India and Asia, the ancestral stock of mangifera migrated east and west and species diversified extensively in the Malaysian and Sumatran rain forests. (Times Internet Limited, 2000).

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b) Taxonomy

The genus Mangifera belongs to the order Sapindales in the family Anacardiaceae, which is a family of mainly tropical species.

Division: Magnoliophyta
* Class: Magnoliopsida
* SubClass: Rosidae
* Order: Sapindales
* Family: Anacardiaceae
* genus: Mangifera
* Species: indica
SCIENTIFIC NAME: Mangifera indica L.

There are hundreds of mango cultivars distributed throughout the world, of which Asia and India have over 500 classified varieties (some say 1 000) have evolved and have been described and 69 species mostly restricted to tropical regions. Perhaps some of these varieties are duplicates with different names, but at least 350 are propagated in commercial nurseries. The highest diversity occurs in Malaysia, particularly in peninsular Malaya, Borneo and Sumatra, representing the heart of the distribution range of the genus. The natural occurrence of all the Mangifera species extends as far north as 27° latitude and as Far East as the Caroline Islands (Bompard and Schnell, 1997). Wild mangoes occur in India, Sri Lanka, Bangladesh, Myanmar, Sikkim, Thailand, Kampuchea, Vietnam, Laos, southern China, Malaysia, Singapore, Indonesia, Brunei, the Philippines, Papua New Guinea and the Solomon and Caroline Islands. Maximum species diversity exists in western Malaysia and about 28 species are found in this region.

However, in the Western Hemisphere, a few cultivars derived from a breeding program in Florida are the most popular for international trade. Locally, many cultivars are used and often seedling trees are grown as a backyard food source (Rieger, 2001). The Horticulture Research Unit of the U.S. Department of Agriculture and the Agricultural Research and Education Centre of the University of Florida, together maintain a germplasm 125 of mango cultivars as a resource for mango growers and breeders in many countries.

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c) Botanical description

Mango trees, grown from seeds are known as "seedlings" have a long straight bole. Tree is sympodially branched. Grafted trees on the other hand are dwarf with spreading branches. However, the shape of the canopy also depends on the space available for its development. Isolated trees, getting sufficient space for their growth may differ in tree shape with the same variety grown in the orchard. On shallow soils the growth is stunted. The compactness of the canopy, branching pattern and leaf component also show ecogeographical dependence. Seedling trees live much more than 100 years whereas grafted ones live only 80 years or less. One of the largest trees known is that from Chandigarh (India), with a trunk of 3.5 m in diameter, limbs of 75 cm diameter. Seedling tree measuring a spread of 125 ft and a girth of 25 ft has been reported to exist in Brazil.

Mango tree

Tree is medium to large (10 to 40 m in height), evergreen with symmetrical, rounded canopy ranging from low and dense to upright and open. Bark is usually dark grey-brown to black, rather smooth, superficially cracked or inconspicuously fissured, peeling off in irregular, rather thick pieces. The Philippine mango trees often reach 15 to 18 m (50 to 60 feet) in height and attain great age. (Figure 4 Manila mango tree) is a large spreading and evergreen with a dense crown, early-ripening. The tree has a rounded canopy ranging from low and dense to upright and open. The leaves are alternately arranged, lanceolate shaped, 6 to 16 inches (15 to 40.6 cm) in length and leathery in texture. Pinkish, amber or pale green-coloured when young, leaves become dark green at maturity. The inflorescence is a many-branched panicle borne at shoot terminals, 2.5 to 16 inches long (6.4 to 40.6 cm), possessing from 550 to more than 4 000 flowers. Flowers are small, pinkish-white, with the majority staminate and the remainder perfect. In Florida, mangoes bloom from December to April depending upon climatic conditions and variety. Pollination is made by various insects such as thrips, flies and to a small extent, honeybees and the fruit is classified as drupes. Mangoes vary in shape (nearly round, oval, ovoid-oblong), size and colour depending upon the variety. Ripe mangoes may be greenish, greenish-yellow, yellow, red, orange, or purple and weigh from a few ounces to more than 5 pounds (2.3 kg). The skin is smooth and leathery, surrounding the fleshy, pale-yellow to deep-orange edible portion. The fruits possess a single large, flattened, kidney-shaped seed that is enclosed in a woody husk. Although the fruit will ripen on the tree, commercially it is usually picked when firm and green for shipment to market. The crop is considered mature when the shoulder of the fruit broadens (fills out) and some fruits on the tree have begun to change colour from green to yellow. Prior to this external colour break, the fruit is considered mature when the flesh near the seed changes colour from white to yellow.

Figure 4. Manila mango trees.

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Root

The tree forms a long unbranched long taproot (up to 6 to 8 metres and more) plus a dense mass of superficial feeder roots. Feeder roots develop at the base of the trunk or slightly deeper; these produce anchor roots and sometimes a collection of feeder roots develops above the water table. The fibrous root system extends away from the drip line. Effective root system of an 18 year old mango tree may observe a 1.2 m depth with lateral spread as far as 7.5 m.

Leaf

The leaves are simple, with no stipules, alternately arranged, 15 to 45 cm in length (Figure 5 Manila mango leaves). The petiole varies in length from 1 to 12 cm, always swollen at the base. It is grooved on the upper side. The phyllotaxy (Inflected forms of leaves on a steam) is usually 3/8 but as the leaves are arranged very closely at the tips they appear to be whorled. Leaves are variable in shapes like oval-lanceolate, lanceolate, oblong, linear-oblong, ovate, obovate-lanceolate or roundish-oblong (Singh, 1960). The apex ranges from acuminate to nearly rounded. The margin is usually entire, sometimes slightly undulated and wavy, rarely twisted or folded. The length and breadth varies from 12 to 45 cm and 2 to 12 cm, respectively, depending on variety and growth. The secondary veins are quite prominent and in some of the varieties range from eighteen to thirty pairs. The upper surface is shining and dark green while the lower is glabrous light green. The leaves appear in flushes. They are flaccid and pendulous when young. The colour of young leaves generally vary form variety to variety, generally being tan-red, pink, yellow-brown in colour. As the leaf grows, its colour changes from tan-red to green, passing through many different shades and become dark green at maturity. The leaves have fibres and crackle when crushed. They strongly smell of turpentine (some cultivars do not smell). The leaves contain considerable amounts of mangiferin (xanthone). In India, this pigment was obtained as "Indian Yellow" from the cow's urine. Cows were fed exclusively with mango leaves and ultimately excessive feeding on leaves lead to their death.

Figure 5. Manila mango leaves.

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Inflorescence

(Please see Figure 6. Inflorescence of manila mango). The inflorescence is pseudo-terminal, originating from a bud, together with the new leafy sprout; there are cultivars with lateral inflorescence. The inflorescence is a narrowly to broadly conical panicle up to a 45 cm long depending upon cultivar and environmental conditions during its development. It is usually bracteate (leaflike plant part) but may sometimes be ebracteate. The bract if present is leafy, elliptical and concave. The colour of the panicle may be yellowish-green, light green with crimson patches or with crimson flush on branches. It is generally pubescent but sometimes may be glabrous. The branching of the inflorescence is usually tertiary, rarely quaternary, but the ultimate branching is always cymose (Singh, 1960). The panicle bears 500 to 6 000 flowers of which 1 to 70 percent are bisexual, the remainder are male depending on the cultivar and temperature during its development.

Figure 6. Inflorescence of Manila mango.

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Flowers

Hermaphrodite and male flowers are produced in the same panicle, usually with a larger number of the later. The size of both male and hermaphrodite flowers varies from 6 to 8 mm in diameter. They are subsessile, rarely pedicellate and have a sweet smell. Pedicels are very short or missing; they are articulate with a panicle branch of the same diameter, which is often mistaken for the pedicel. The calyx is usually five partite. The lobes are ovate-oblong and concave. The corolla consists of five pale yellow petals (rarely four to eight) that are twice as long as the calyx and contain three to five ridges on the ventral side. The petals are in bud imbricate and slightly contorted. They are thin, yellowish and after expanding horizontal, the upper half rather irregularly and not very pronouncedly reflexed, they are free at their base. The ridges are slightly dark. The upper half and the margin of the petal are white. On fading, the petals become pinkish. Between the corolla and androecium there is an annular, fleshy and five-lobed disc (Singh, 1960; Kostermans and Bompard, 1993). The androecium consists of stamens and staminodes, altogether five in number, of which usually one, or rarely two, is fertile and the rest are sterile. However, in cultivar Pico, three fertile stamens have been reported (Juliano and Cuevas, 1932). As many as ten stamens, which occur in other members of the genus, may also occasionally be found in the form of primordia only. All the stamens are inserted on the inner margin of the disc. The position of the fertile stamen and pistil may be either parallel or oblique to each other. The fertile stamens are longer than the staminodes and are nearly equal to the length of the pistil. The colour of the anther is pink, which turns purple at the time of shedding. The ovary is sessile, one-celled, oblique and slightly compressed in its lateral aspect. It is placed on the disc. The ovule is anatropous and pendulous and shows one-sided growth. The style arises from the edge of the ovary and ends in a simple stigma. Sometimes three carpels may develop in a flower.

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Pollen and pollination

The pollen grains are of variable shapes, with the size varying from 20 to 35 micron. Small amounts of pollen are produced in mango. The grains of pollen are sphaeroidal to prolate sphaeroidal, radially symmetrical, subangular in polar view, isopolar, with a few giant triploid ones of up to 50 micron. Further they are 3-monocolporate, goniotreme, sides convex-subprolate; apertures equidistant and zonal with ecto-aperture (colpus) extends slit-like from pole to pole. The mango inflorescence is a branched terminal panicle, 4 to 24 inches long, comprising from a few hundred to several thousand individual flowers, requiring up to a month for all to open. The number of panicles may range from 200 to 3 000 per tree with 500 to 10 000 flowers per panicle yield 100 000 to 30 million flowers per tree. The proportion of perfect to staminate flowers may vary from 1:4 to 2. Sometimes, the entire tree comes into bloom at one time, covering itself with sweet-scented flowers. There are perfect and staminate flowers on the same panicle. The perfect flower, 5 to 8 mm long, has a globular ovary (rarely two or three) and a lateral style, which is absent in the staminate flower. Both generally have one, but sometimes two or even three functional stamens and several sterile staminodes. There are usually five greenish-yellow sepals and three to nine, but usually five, cream-coloured petals that take on a pinkish tinge before falling (Naik and Rao 1943). In the perfect or hermaphrodite flower, a nectar-secreting fleshy disk surrounds the ovary. The stamen is on the outer margin of this disk. The pistil and stamen are the same length; therefore, pollinating insects that feed on either nectar or pollen are likely to transfer pollen from the anther to the stigma (Juliano and Cuevas 1932, Sturrock 1966). The flower opens early in the morning and the stigma is immediately receptive. Maximum pollen shedding is from about 8 to noon. This delayed pollen shedding can result in inadequate stigma fertilization (Spencer and Kinnard 1956). When the flowers open, they secrete nectar in considerable quantity, which attracts a large number of insects (Mukherjee, 1953); however, relatively little pollen is produced on the anther (Rajans, 2001).

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Pollination Requirements: There has been some lack of agreement on the pollination of mangoes. Young (1942) made pollination studies on the 'Haden' mango in Florida, which he said made up 90 percent of the commercial plantings in the state (the 'Tommy Atkins' is the current popular cultivar) and found no significant difference between percentages of set in self- and cross- pollinated flowers. Sturrock (1944) also considered the flowers self-fertile. This self-fertility was supported by the earlier work of Popenoe (1917), who stated that the mango is self-fertile but cross-pollination increases fruit set. However, Singh et al. (1962) reported that cross fertilized flowers produced set fruit whereas self fertilized ones did not, indicating a certain degree of self-sterility. The actual degree of self-fertility and sterility in individual cultivars has not been determined, but there is apparently some variation. Self-sterility is not, however, a major problem in fruit set (McGregor, 1976).

Within the cultivar there is a definite need for transfer of pollen from anther to stigma by an outside agent. Popenoe (1917) stated that some of the embryos are capable of development without fertilization; however, Naik and Rao (1943) obtained no parthenocarpic fruit set of more than 100 000 flowers studied. Fraser (1927) stated that fruit bud formation and pollination were the two big problems in growing mangoes. He pointed out that in some cases only 2 to 3 percent of the flowers on a panicle are perfect while in others 60 to 70 percent are flawless. Wolfe (1962) concluded that getting flowers to set fruit was more of a problem than getting the trees to produce flowers. The effect of cool weather adversely affects pollen tube growth, but this was not considered to be a factor of major importance by Young (1955). The studies indicate that the need for cross-pollination between mango cultivars is not critical, at least for most cultivars, but there is need for pollinating insects to transfer the pollen from anthers to stigma within the cultivars to obtain satisfactory crops of fruit.

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Pollinators: Several agents have been given credit as pollinators of mango. Wagle (1929) showed that there was some self fetilization and some wind pollination, but insects (bees, ants and flies) played an important part. Popenoe (1920) disagreed with other writers that the mango is wind pollinated. He pointed out that the flowers have none of the characteristics of a wind-pollinated flower and he considered the mango to be an insect-pollinated plant. Galang and Lazo (1937) and Singh (1969) agreed with him. Recent studies in India showed that plants caged to exclude all insects set no fruit and gall-midges were ineffective as pollinators, but a plant caged with a colony of honeybees where harmful insects were excluded set a heavy crop. Singh (1961) reported that over 65 percent of the perfect flowers were never pollinated. This is a strong indication that wind is not an effective pollinating agent. Complaints about lack of adequate fruit set in larger plantings particularly of monoclonal cultivars are frequent (Singh, 1969). Fraser (1927) concluded that the important problem was finding out which insets were important as pollinators. The statement was made by Singh (L.B.) (1960) that honeybees do not visit mango flowers, but Singh (1954) listed this plant as a source of pollen and nectar for bees. Popenoe (1917) reported that honeybees were the most important hymenopterous insect visitor to the mango flowers, but the number present was variable, possibly because of the location of apiaries or other relatively more attractive flora. This probably explained the low population of honeybees reported by Simao and Maranhao (1959).

Pollination Recommendations and Practices: There is no indication that the recommendation by Young (1942) to place colonies of honey bees in mango groves has become an accepted practice; however, the chances are likely that such bee usage is needed today much more so than when his studies were made. The evidence is quite strong that concentration of colonies of honeybees within the mango grove would result in increased floral visitation and possibly more stabilized set of fruit, particularly in some years. The mango flowers do not appear to be overly attractive to honey bees and they tend to open in large numbers at a time of year when many other flowers are also available, so visitation in commercial groves is likely to be far below that necessary for maximum floral visitation. If such is the case, a heavy concentration of colonies in the grove, possibly three to six per acre, may be necessary to obtain maximum fruit set.

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Fruit

(Please see Figure 7. Typical mangoes of Manila, Ataulfo and Oro varieties). The fruit is a more or less compressed, fleshy drupe. It varies considerably in size, shape, colour, presence of fibre, flavour, taste and several other characters. The most characteristic feature of the mango fruit is the formation of a small conical projection developing laterally at the proximal end of the fruit, known as the beak. It may be quite prominent in some, less so in others, while in some varieties it is represented merely by a dot. A wide sinus is always present just above this beak. The pistillate area of the fruit located near the base of the beak is known as the nak. The shape of the fruit varies from rounded to ovate-oblong or longish, with the length varying from 2.5 to 30 cm in different varieties. The base may be depressed or elevated or may be intermediate. The skin is gland-dotted and at maturity its colour exhibit different mixtures of green, yellow and red shades. It may be smooth or rough. Each mango has a single flat seed, surrounded by flesh, which is either yellow or orange. This flesh is rich in vitamins A, C and D. The acrid juice, with turpentine like smell, present in the stalk or sometimes in the fruits, is known as chenp in Hindi is due to myrcene and ocimene. Its main irritating constituent has been identified as an allergenic urushiol, 5-heptadecenylreorcinol. The harvesting itself is a delicate process because the fruit is easily bruised, so harvesting is usually done by hand.

Figure 7. Typical mangoes of Manila, Ataulfo and Oro varieties.

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d) Cultivars (See Figure 8. Manila mango trees).

Apart from numerous seedling varieties, more than a thousand vegetatively propagated mango cultivars have been reported. Most of these have originated as chance seedlings selected earlier and further maintained asexually. Majority of these cultivars is of Indian origin and representation from other parts of the world is limited in number (Table 1).

Table 1. Fruit characteristics of mango cultivars in major producing countries.

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Figure 8. Manila mango trees.

e) Growth habit

Mangoes are well adapted to many soil types. In Florida, trees growing in light sand and limestone soils must be fertilized periodically for satisfactory growth and fruit production. Generally, mango trees (See Figure 9 for soil type for Manila mango) tolerate some flooding or wet soil conditions; however, the response among trees is variable. Flooding stress symptoms include leaf wilting and desiccation, stem dieback, reduced growth and tree death. Previous and current environmental conditions and plant size and health affect the response to wet conditions (Crane and Campbell, 1994).

Figure 9. Soil type for Manila mango.

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Description of mango tree

Mango trees are very tall in height and have thick, leathery leaves. From their branches, long stems hold clusters of fruits that can range from a few ounces to a few pounds.

Foliage and flowers (See Figure 10 Manila mango tree inflorescence)

Figure 10. Manila mango tree inflorescence.

f) Traditional practices

(See Figure 11. Traditional practices for Manila Mango). For best results, irrigation water should contain less than 1 000 ppm total salts. It is essential to provide adequate water from the first sign of flower spikes through to harvesting. The critical time for irrigation is during fruit development; water stressing the trees at this time can reduce yield.

The irrigation schedule will depend on the tree age, growth stage of the fruiting trees, prevalent temperature and rainfall.

· Growth stage 1: Pre-flowering (six to eight weeks before flowering);
· Growth stage 2: Flowering to end of harvest; and
· Growth stage 3: End of harvest to pre-flowering.

Only generalized recommendations of mango fertilizer requirements can be made. It is important to take regular leaf samples for good nutritional management. As nutritional levels will change in the tree during the season, be sure to sample the trees at the same time each season. The most stable time of year for sampling is just prior to flowering. Take leaf samples from the last mature flush, from dormant shoots.

Young trees in all areas require a basal fertilizer at planting time and in small regular NPK applications to ensure maximum growth during the juvenile phases. When fruiting commences, nutrition must be closely monitored. Excessive applications of nitrogen contribute to poor quality fruit - soft nose, green fruit, uneven ripening and poor blush.

For the first three years, fertilize young trees every three months with 40 g of urea per tree, per year of age, that is, up to 120 g of urea applied four times per year in the third year. From the fourth year, apply fertilizer after flowering to increase fruit size and after harvesting to provide strong shoot growth on which the following year's crop will be borne. Do not apply during the stress period of flower initiation in July and August (AWA, 1998).

Figure 11. Traditional practices for Manila Mango.

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Planting

Prior to planting, field should be deeply ploughed, harrowed and levelled. Pits of proper size should be dug at appropriate distances and filled by adding sufficient quantity of farmyard manure. The grafts to be planted should be procured from reliable nurseries few days before actual transplanting.

a) Time of planting: The best time for planting is when there is sufficient moisture in the atmosphere. In the area of heavy rainfall, the best time of planting mango is the end of the rainy season. In tracts where the rainfall is less, the planting can be done in the early part of the monsoon for better establishment. The planting should be done in the evening; otherwise if the day turns out to be unusually hot or dry, the plants may wither due to excessive loss of water. If the sky is overcast, planting can be done during daytime also

b) Planting distance: The planting distance varies according to variety, the fertility level of the soil and general growth conditions in the area. Where the growth is excessive, the distance should be 12 x 12 m, but in the dry zones where the growth is less, it can be regulated to about 10 x 10 m. For high density planting, the distance can be 5 x 3 or 5 x 2.5 or 3 x 2.5 or 2.5 x 2.5 m.

c) Size of pits: In locations where the soil is loamy and deep, pits of 0.5 x 0.5 x 0.5 m be dug at desired distances. However, in shallow and hill soils, the pits should at last be of 1 x 1 x 1 m size.

d) Filling of pits: The pits should be filled with the original soil mixed with 50 kg well rotten farmyard manure. In the top two-third portion, the proportion of the manure and soil may be kept as 1:3. If the soil is having infestation of white ants, 200 to 250 g of aldrex or BHC dust may also be mixed. In case of stony soils, it is better to remove all the stones from the excavated material and remaining soils should be mixed with soil scrapped from the left over area and FYM. The pits should invariably be filled before the rainy season, so that there is maximum settling down before the advent of heavy rainfall and much before planting.

e) Planting of grafts: The plant with its ball of earth intact should be taken out of the soil or pot. The plant can then be placed with the help of a planting board in the centre of the pit by excavating as much soil as necessary to accommodate the root-ball. The moist soil of the pit is then pressed all around the root ball to complete the planting process. A small basin is then made and the plant is properly watered. The planting should not be done so deep as to bury the graft-union in the soil or so high as to expose the upper roots. It is always better to adjust it at the same height/depth at which it was in the pot or the nursery bed.

f) Training and pruning: Normally, mango trees require very little or no pruning. However, the training of the plants in the initial stages is very essential to give them proper shape. Especially when the graft has branched too low, the process of training becomes very important. At least 75 cm of the main stem should be kept free from branching and the first leader/main branch may be allowed after that. The main branches should be spaced in such a way that they grow in different directions and are at least 20 to 25 cm apart, otherwise there are chances of breakage due to smaller crotch angles and heavy top. The branches which exhibit tendency of crossing and rubbing each other should be removed in the pencil thickness stage, otherwise they break by rubbing each other at a later stage and create complications. Secondly, if the centre is closed the fruits produced are of poor quality having less colouration in the absence of sufficient sunlight. By following the above practice and after giving proper shape to the trees, there will be much less scope for future pruning except removal of diseased, pest infested or dried shoots/wood.

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Labour

Training and supervision of labour are critical to a successful harvesting operation. Constant supervision is necessary to maintain quality and reduce subsequent spoilage of produce. Training is required in both general principles and crop specific techniques relating to maturity selection, detachment method, maintenance of equipment, field hygiene and division of labour. Some of the more important areas are:

Division of labour

Teams of workers must work systematically through a plot or field, experienced staff removing the crop and others carrying it to collection points. If crops are relatively inaccessible, as with older mango trees, pickers climbing in the trees if fruit is to be harvested must take great care free of damage. Whenever possible, planting densities and pruning techniques should be chosen which minimize tree size. Mangoes are harvested with the aid of a picking device attached to the end of a long bamboo pole. The picking device consists of a pair of string-operated shears and a collection sack. When picking mangoes, it is very important to leave a long stem. Immediately after being picked, all mangoes that are to be exported to countries such as the United States of America undergo a post harvest hot water treatment. Mangoes are harvested several times during the season. On any individual tree, fruits may be harvested daily, since the earliest bloom matures and ripens weeks before the later bloom.

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g) Planting and Preliminary Actions

Propagation

(See Figure 12 and Figure 13. Propagation of Manila mango).

Mangoes are raised from seed or propagated vegetatively. Propagation from seed, though easy and cheap, is unable to perpetuate characters of the parent tree because most commercial varieties in India are cross-pollinated and monoembryonic. Plants also take more time to bear fruit. Accordingly, several methods of vegetative propagation have been tried with varying degree of success. However, it is essential to raise seedlings to be used as rootstocks. For this purpose, stones should be sown in June to July in beds mixed with well-decomposed farmyard manure at the rate of 8 to 10 tonnes/ ha. Alternatively, 25 kg nitrogen (N) per hectare may be applied in the form of urea, can or any other available inorganic source in two split doses at about two months interval after the leaves have become green. When the seedlings attain the age of 2 to 3 months, they should be transplanted in well-prepared beds or pots. In this season, proper care should be exercised in irrigating the young transplanted seedlings. The seedlings should also be protected from frost by putting the pots under big trees or thatching the young seedlings in the field.

Figure 12. Propagation of Manila mango.

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Plants are generally propagated using random seedling rootstocks. The polyembronic rootstocks, however, have shown a promise in producing plants of uniform size and vigour. Moreover, these rootstocks have indicated possibility of inducing dwarfing and earlier bearing and are under test. Various methods employed in vegetative propagation of mango are described below:

a) Inarching: The method of inarching or approach grafting is quite cumbersome and time consuming, but it is still the leading method for commercial propagation of mango plants. The method consists of uniting the selected shoot (scion) of a desired parent tree (mother plant) with the potted or transplanted seedling (rootstock) by approach grafting. For this purpose, about one-year-old seedlings are most suitable when they attain a height of about 30 to 45 cm and thickness ranging from 0.75 to 1.5 cm. These seedlings are either grown in pots or under the mother plant from which the grafts are to be prepared, depending upon the availability of suitable branches. Generally, one-year-old twigs of the scion tree about 60 cm in length and nearly of the same thickness as that of the stock is chosen for grafting. Young and non-bearing trees should not be selected as mother plants.

Inarching should be done during the growing period when the tree is in active sap flow condition termed as active growth period. A hot and very dry period, as well as heavy rainfall during the inarching period is not suitable. The end of the monsoon in heavy rainfall areas and early monsoon in the light rainfall areas is the best period for inarching. In north India, July is the best month for inarching. In the more equitable climate of south India, the operation can be done any time between July and February. A thin slice of bark and wood, about 5 cm in length, 7.5 mm width and 2 mm deep, is removed by means of a sharp grafting knife from the stem of the stock as well as from the scion branch. The dimensions can be proportionately increased or decreased according to the thickness of the stock and scion. The cuts thus made should be absolutely flat, clean, boat shaped, even and smooth. The ends of these cuts should be round and not angular. The cut surfaces of both, i.e., stock and scion are made to coincide facing each other so that there remains no hollow space between the two. These are then tightly tied by polythene / alkathene strips of about 1.5 cm in width and preferably of 200 gauge thickness, which has proved to be a good tying material.

After about one month of operation, the scion below the graft union and stock above the graft union should be given light; shape cuts at weekly intervals such that grafts can finally be detached while giving the fourth cut. In the last stage, the top of the stock above graft union should also be removed completely.

Figure 13. Propagation of Manila mango.

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b) Veneer grafting: This method of propagation possesses promise for mass scale commercial propagation. The method is simple and can be adopted with success. The rootstocks as mentioned, for inarching are suitable for this method also. For conducting this grafting operation, a downward and inward 30 to 40 mm long cut is made in the smooth area of the stock at a height of about 20 cm. At the base of cut, a small shorter cut is given to intersect the first so as to remove the piece of wood and bark. The scion stick is given a long slanting cut on one side and a small short cut on the other so as to match the cuts of the stock. The scion is inserted in the stock so that the cambium layers come on the longer side. The graft union is then tied with polythene strip as recommended for inarching. After the scion takes and remains green for more than 10 days the rootstock should be clipped in stages. The scion wood to be used for veneer grafting requires proper preparation. The desired shoots should be defoliated at least one week prior to grafting so that the dormant buds in the axis of leaves become swollen. The best time for this method is the same for different regions as for inarching.

c) Budding: Although success of budding in mango was reported in the beginning of this century, budding still continues to remain in experimental stage as far as commercial mango propagation is concerned.

d) Stone Epicotyl grafting: Mango is generally propagated by inarching and veneer grafting. These methods are time consuming. Stone epicotyl grafting is a new technique of mango propagation. This method is simple, cheap and quick. Fresh mango stones are sown in the nursery beds. After germination, seedlings with tender stems having coppery leaves are lifted with stones still attached. The roots and stones are dipped in 0.1 percent Bavistin solution for 5 minutes after washing the soil. The seedling stems are headed back leaving 6 to 8 cm long stems. A 4 to 6 cm longitudinal cut is made running down through the middle of the stem. A wedge shaped cut starting on both sides is made on the lower part of scion stick. The scion stick should be 4 to 6 months old and 10 to 15 cm long containing plump terminal buds. The scion stick is then inserted in the cleft of the seedlings and tied with polythene strips. The grafts are then planted in polyethylene bags containing potting mixture. The bags are then kept in the shade protecting from heavy rain. When the scion sprouts and the leaves become green, the grafted plants should be planted in nursery beds. July is the most suitable month for stone grafting.

e) Softwood grafting: The technique of softwood grafting is similar to that of cleft or wedge grafting. In this case, grafting is done on newly emerged flush having bronze coloured leaves and stem. This method is useful in in-situ grafting. The scion wood to be used should be defoliated 10 days prior to the grafting and having same thickness as that of terminal shoot. The graft should be secured firmly using 1.5 cm wide and 4.5 cm long, 200-gauge polyethylene strip. July and August are the best months for softwood grafting.

f) Air layering: Air layering can be done successfully in mango using indolbutyric acid (IBA) or naphtalen acetic acid (NAA) 10 000 ppm in lanolin paste. Success up to 50 percent has also been obtained by using a root promoter. The air-layers can be used for permanent planting or for raising uniform rootstocks.

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Irrigation

Amount and frequency of irrigation depends upon the type of soil, prevailing climatic conditions, especially rainfall to be given and its distribution and age of trees. No irrigation is required during the monsoon months unless there are long spells of drought. During the first year when the plants are very young with shallow root system, they should be watered every 2 to 3 days in the dry season. Trees in the age group of 2 to 5 years should be irrigated at 4 to 5 days interval. The irrigation interval could be increased to 10 to 15 days for 5 to 8 years old plants during dry season. When trees are in full bearing stage, generally 2 to 3 irrigations are given after the fruit set. Profuse irrigation during 2 to 3 months proceeding the flowering season is not advisable. Irrigation should be given at 50 percent field capacity. Generally, intercrops are grown during the early years of plantation and hence frequency and method of irrigation has to be adjusted accordingly. It is advisable to irrigate the mango plants in basins around them, which can be connected in series or to the irrigation channel in the centre of rows. The ntercrops need to be irrigated independently as per their specific requirements. In monocropping of mango also, basin irrigation is preferable with a view to economize water use.

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Fertilization

Soil fertility has a direct effect on all aspects of crop growth and development. In some cases, post-harvest disorders can be linked directly to the deficiency of a particular mineral, but often other environmental factors such as water stress are involved. "Spongy tissue" symptoms in mango have been linked to mineral deficiency and copper and iron deficiencies cause abnormal peel development in citrus fruits.

Nutrient uptake in mango is from large volume of soils. Therefore, it is able to sustain growth even in low fertility soils. However, its efficient management involves the replenishment of the nutrients used-up by the tree for its growth and maintenance, harvested produce and natural losses from soils through leaching and run off. Even the under-nourished trees can be revived by suitable supplementation of nutrients through fertilizers. The idea of applying manure to fruit bearing trees is also to secure regular fruit production. Recommendations based on very limited research and also on experience gained by the orchard experts are given below (Rajans, 2001).

Application of manure to mango plants starts right from planting operation in the orchard. First application is made at the time of filling of the pits. Fertilizer application during the first year of planting may be given as 100 g N, 50 g P2O5 and 100 g K2O per plant. The above dose should be increased every year up to 10 years in the multiple of first year's dose. Accordingly, a 10-year-old tree should receive 1 kg N, 500 g P2O5 and 1 kg K2O. This dose should continue to be applied in subsequent years also. Application of 50 kg well-decomposed organic manure should be given each four year to create proper soil physical environment. For trench application of fertilizers, 400 g each of N and K2O and 200 g of P2O5 per plant should be given.

The application of micronutrients is not recommended as a routine. Need based supplementation are essential when these become a limiting factor for production. It is advisable to apply micronutrients through foliar sprays. Fertilizers may be applied in two split doses, one half immediately after the harvesting of fruits and the other half 2 to 3 months later, in both young and old orchards, followed by irrigation if there are no rains. Foliar application of 3 percent urea in sandy soils is recommended before flowering. First of all, the weeds should be removed from basins. The mixture of recommended dose of fertilizers should be broadcast under the canopy of plant leaving about 50 cm from tree trunk in old trees. The applied fertilizer should be amalgamated well up to the dept of 15 cm soil. To increase fertilizer use efficiency, fertilizers should be applied in 25 cm wide and 25 to 30 cm deep trenches dug around the tree 2 m away from trunk.

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Interculture

Interculture in orchards is necessary for the proper upkeep of mango plantation. The removal of weeds not only avoids the competition for essential nutrients but also creates better physical soil environment for plant growth, particularly root development. It also helps in water movement in soil and in controlling some of the insect pests. Moreover, it ensures proper incorporation of the applied plant nutrients in soil and reduces their loss. Frequency and the time of interculture operations vary with age of the orchards and existence of intercrops. Immediately after planting the mango, the weed problem may not exist, but it is advisable to break the crust with hand hoe each time after 10 to 15 irrigations. However, subsequent hoeing may be done depending on weed growth in the basin. If the intercrops are not being raised in the pre-bearing stage due to some reasons, the area between the basins should be ploughed at least three times a year, i.e., pre-monsoon, post-monsoon and in the last week of November. Interculture operations are equally important for the bearing mango orchards. First ploughing should be done before the onset of rains. This will help in checking run-off losses and facilitate maximum retention of water in the soil. Orchard may be ploughed again after the rainy season is over in order to suppress weed growth and to break capillaries. Third ploughing may be done in the last week of November or first week of December with a view to checking the population of mango mealy bugs. (Rajans, 2001).

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