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Mickelbart, M.V. 1996. Sapodilla: A potential crop For subtropical climates. p. 439-446. In: J. Janick (ed.), Progress in new crops. ASHS Press, Alexandria, VA.

Sapodilla: A Potential Crop For Subtropical Climates

Michael V. Mickelbart


  1. NOMENCLATURE
  2. TREE DESCRIPTION AND MANAGEMENT
  3. PROPAGATION
  4. FLOWERING AND POLLINATION
  5. FRUIT DESCRIPTION AND USES
  6. POSTHARVEST STORAGE
  7. CULTIVARS
  8. REFERENCES
  9. Table 1

Sapodilla (Manilkara zapotilla, Sapotaceae) is native to Central and South America, specifically from the Yucatan Peninsula of Mexico to Costa Rica, where the largest population of native trees still exists (Gilly 1943). It is now widespread throughout the tropical regions of the world, including Central and South America, the West Indies, India, and Florida in the United States.

Sapodilla is the source of chicle, the principle ingredient in chewing gum. The chicle is extracted from the trunk of the tree as a white latex exudate. Today, sapodilla is cultivated for its fruit in most areas. Although synthetic gums are primarily used, some countries such as Mexico, Venezuela, and Guatemala, still grow sapodilla for chicle.

Sapodilla is grown on a commercial basis in India, the Philippines, Sri Lanka, Malaysia, Mexico, Venezuela, Guatemala, and some other Central American countries. India is the largest producer of sapodilla fruit with current production around 24,000 ha (Chadha 1992). Sapodilla is widely planted in south Florida, where the fruit is marketed locally and shipped to northern and eastern U.S. markets. The fruit, however, is not commonly seen in the United States. In southern Mexico and Central America where sapodilla is native, it is considered to be one of the best of the tropical fruits.

The future of sapodilla appears to be promising, given the attention the crop is receiving from growers and consumers in many countries. Indian production of sapodilla continues to grow and there is an active research program in that country with specific goals toward improving storage, transport, and marketing strategies. Sapodilla has been identified by the Ministry of Agriculture in Malaysia to be promoted under the program for development of its fruit industry (Bakar and Abdul-Karim 1994). The fruit is also gaining popularity as a specialty fruit in restaurants in North America and production of sapodilla as a commercial crop seems to be a possibility in areas where environmental conditions are mild.

NOMENCLATURE

The name sapodilla is derived from the Spanish word zapotilla, meaning "small sapote." The fruit, commonly referred to as sapodilla in the U.S., is also known as chicku, chiku (India), chicopote, chicozapote (Mexico), dilly (Bahamas), kauki (Southeast Asia), mespel (Virgin Islands), mispu, mispel, mispelboon (Surinam), muyozapot (El Salvador), naseberry (British West Indies), nispero (Puerto Rico), sapatija, sapodilla plum, sapodille (Dutch West Indies), sapota, sapote (Cuba), sapoti or sapotilha (Brazil), sapotille, sapotillier (French West Indies), zapote, zapote chico, or zapotillo. The profusion of names for the fruit is probably due to the many small, isolated growing areas it occupies, where names are often derived from local words. The small-market characteristics of the fruit have helped to keep it in obscurity.

The botanical name of the fruit is no less confusing. Both Manilkara and Achras are commonly used as generic names and there appears to be no agreement among botanists or horticulturists as to the proper term. Sapota (zapota) or sapote (zapote) are commonly used as the species name, although this too is variable among regions and authors. Gilly (1943) addressed this problem of confused nomenclature. It seems the generic name Achras, given by Linnaeus, was based upon a plate and description by the botanist Plumier. Unfortunately, the plant described by Plumier is not sapodilla, leading to the misnaming. Gilly suggests that Manilkara zapotilla (Jacq.) Gilly is the only proper name since Manilkara is the earliest recorded name of the group to which sapodilla belongs and zapotilla was specifically applied to sapodilla at the time of its publication. Still, the nomenclature of this species remains confused.

TREE DESCRIPTION AND MANAGEMENT

The tree is a medium to large evergreen tree reaching 12 to 18 m in the tropics, although some trees may reach 40 m. Tree size would likely be much smaller in subtropical regions such as Southern California, where cool winters would slow growth for a portion of the year. The canopy is dense, often with a rounded crown, but sometimes with a more pyramidal shape. The trunks of the trees are reported to attain a diameter of 2 to 3.5 m in Central America. The glossy, dark green leathery leaves clustered toward the tips of the branches are ovate-elliptic to elliptic-lanceolate, 5 to 12.5 cm long, 6 cm wide.

Being a strictly tropical tree, the sapodilla is limited in the United States to the southern coastal region of Florida and possibly some southern coastal areas of California. Young trees are injured or sometimes killed at temperatures of -1° to 0°C, while mature trees can withstand temperatures as low as -2° to -3°C with only minor damage. Temperatures above 41°C during flowering or fruiting can cause flower abortion or fruit scalding.

Sapodilla has proven to be tolerant of dry conditions, and its ability to thrive on poor soils makes it an ideal fruit tree for less-than-optimum growing areas. The tree has shown ability to withstand extended periods of waterlogging, and trees are grown on most soil types, from clay soils to almost pure limestone. Sapodilla is remarkably tolerant of high levels of root zone salinity (Mickelbart and Marler 1996), a rare characteristic in tropical fruit species. It has also proven tolerant of salt spray off the coast of Florida, indicating it may thrive on the subtropical coasts of other regions as well. Sapodilla appears to perform better, in fact, in the coastal regions of the areas in which it is grown. Still, the fact that sapodilla has, at least initially, been successfully grown in the hot, arid desert regions of India suggests that the tree may be grown in some desert areas of California, although the effect of extremely high temperatures on such physiological events as flowering and fruit set may limit production.

Sapodilla is a shallow-rooted tree, with more than 80% of the roots located within the top 75 cm of soil, concentrated within an area half the width of the canopy (Avilan et al. 1981; Bhuva et al. 1991). About 66% of the moisture extracted from the soil is in the first 75 cm. This root morphology suggests that irrigation may be economically feasible in areas of low rainfall. Pruning does not appear to be necessary for at least the first ten years of growth, except possibly skirting of the lower branches.

Young trees require irrigation, especially during lengthy dry periods, and mature trees bear more consistent, higher quality crops with regular irrigation. Trees four years of age and older are generally able to cope with extended dry periods. Irrigation of mature trees increases fruit yield and canopy volume (Bhuva et al. 1990), although water use efficiency decreases with increased irrigation (Bhuva et al. 1991), suggesting that irrigation may not be economically feasible in areas which receive sufficient rainfall.

Fertilization appears to have a favorable effect on fruit yield (Bhuva et al. 1991) and on fruit quality characteristics such as total soluble solids and pulp:seed ratio (Durrani et al. 1982). Potassium is taken up in larger amounts than any other nutrient in sapodilla (Rao 1979; Avilan et al. 1980; Sulladmath 1983). Potassium fertilization seems to have a favorable effect on fruit set (Laborem et al. 1981), especially when done in conjunction with an application of phosphorus (Durrani et al. 1982). In fact, Avilan et al. (1980) found a linear relationship between fruit yield and potassium uptake.

Insects and disease are rarely a problem on sapodilla, although leaf miner and stem borer are sometimes minor problems. Phytophthora palmivora (Butler) may cause fruit rot in the lower fruits on the canopy if water directly contacts the fruit, especially during periods of elevated temperatures and high humidity. Leafspot (Phaeophleospora indica Chinnappa) is also reported to be a problem in India (Balasubramanian et al. 1988).

PROPAGATION

Sapodilla is vegetatively propagated, due to the great variability in progeny from seed, as well as the length of time from planting to fruit set, often taking as much as 6 to 10 years. Air layering is the most common means of propagation in India and there has been a fair amount of research regarding optimal treatment of air-layered plants. Workers in India have found that using recently-produced branches, along with etiolation and application of a growth regulator such as IBA or NAA results in optimal growth of air-layered plants (Chadha 1992).

Veneer grafting resulted in the highest percent survival and moderate root growth in a study comparing various propagation techniques including side grafting, side inarching, tongue grafting, whip grafting, and saddle grafting (Hussain and Bukhari 1977). Tongue grafting resulted in the lowest percent survival, although the plants produced had significantly larger root systems than those produced by the other methods. Malo (1967) describes a successful method for veneer grafting young sapodilla plants designed to efficiently propagate large numbers of sapodilla.

Softwood grafting was successful (ca. 80% survival) in a study conducted in India (Kulwal et al. 1985). The greatest success was obtained when scion wood was defoliated 8 days prior to removal and when grafting was done during the summer months.

While sapodilla seedlings are often used as rootstocks for grafted plants, some other species may be suitable and contribute to the management of sapodilla orchards. Wild dilly [Manilkara emarginata (Bakar) Lam. & Meeuse] (Ogden and Campbell 1980) and Manilkara hexandra (Roxb.) (Chandler 1958) have been proposed as possible dwarfing rootstocks for sapodilla.

FLOWERING AND POLLINATION

The small white flowers of sapodilla are borne on short pedicels in the leaf axils. Piatos and Knight (1975) found sapodilla to be self-incompatible, indicating that cross-pollination might be necessary. While production of some cultivars such as 'Prolific' is high in areas such as Florida, fruit yield among cultivars is variable, a characteristic which may be due to self-incompatibility. Gonzalez and Feliciano (1953) examined flowering and fruit set in 'Ponderosa' sapodilla and found that the trees could not be self-pollinated, either naturally or artificially. The best method of pollination was determined to be cross-pollination by hand, which resulted in a 39.6% fruit set. Open pollination resulted in only 5% fruit set in that study. Similar results were observed in 'Kalipatti' sapodilla by Relekar et al. (1991). Mulla and Desle (1990) found that the highest percent fruit set was observed in trees cross-pollinated with pollen of the same cultivar and ranged from 20 to 34%. There was no sign of parthenocarpy and self-pollination resulted in only negligible fruit set in some of the cultivars examined.

Reddi (1989) conducted a series of studies in which he showed that thrips (Thrips hawaiiensis Morgan and Haplothrips tenuipennis Bagnall) are the principle pollinators of sapodilla in India. The thrips apparently take shelter in the flowers and live on the pollen grains, nectar, and stigmatic exudations. They collect pollen grains while feeding on these components and transfer then to other flowers when the food reserves are exhausted. Bees have been observed in flowering sapodilla plantings (Sambamurty and Ramalingam 1954), although examination of the insects indicated that they were not carrying pollen.

Reddi's study showed several traits which indicated that wind is not an important pollinating agent, nor are large insects. Sambamurty and Ramalingham (1954), however, suggest that wind is an important factor in sapodilla pollination. Reddi also showed that sapodilla flowers are not self-pollinating, although pollen transfer is generally limited to a single tree unless trees are closely spaced. This information would provide evidence that sapodilla is not self-incompatible as previously suggested. Pollen size and viability are quite variable between cultivars, possibly causing the varied results in fruit set (Minhas and Sandhu 1985).

Much like avocado, sapodilla produces many more flowers than developed fruits. The great variability in fruit set may be due to differences in flower abortion or fruit drop, although differences in this phenomenon between cultivars has not been specifically examined in sapodilla. The major period of fruit drop occurs in the first five weeks following fruit set and as little as 1.6% of the flowers produced by a tree may develop into fruit (Relekar et al. 1991). Fruit set is highly variable, even within a cultivar. Gonzalez and Feliciano (1953) suggested that tree vigor may be related to flower production and fruit set.

FRUIT DESCRIPTION AND USES

The fruit of sapodilla is small, ranging from 5 to 9 cm in diameter with a round to egg-shaped appearance, from 75 to 200 g in weight. The rough brown skin, which gives the fruit a somewhat unattractive appearance, encloses a soft, sweet, light brown to reddish-brown flesh. The flesh is often gritty, much like a pear, and it can hold up to 12 flat, smooth black seeds, although some fruit are seedless. Superior strains have a fine smooth texture with a slightly fragrant and sweet flavor.

Fruit development follows a sigmoidal pattern (Sulladmath et al. 1979; Abdul-Karim et al. 1987). The initial growth phase is due to cell division and involves maturation of the embryo within the fruit. A phase of greatly reduced growth follows, until a second rapid growth phase occurs, during which time growth is due to cell enlargement. This second growth phase is the time when maximum growth occurs, between 5 and 7.5 months from fruit set (Lakshminarayana and Subramanyam 1966). The fruit are suitable for harvesting after the first growth phase, although higher quality fruit are obtained if they are harvested following the second growth phase, when there is a dramatic increase in sugar content of the fruit.

Fruit maturity occurs anywhere from 4 to 10 months following fruit set, depending on variety, climate, and soil conditions. In south Florida and the Virgin Islands, the fruit appears throughout the year, with a peak season from May to Sept. Fruit is also produced throughout the year in Malaysia. In the desert regions of India, the fruit ripens primarily in July and Aug. Seasonal variation in fruit shape and size is not uncommon and great variation exists among seedling fruits.

Because immature sapodilla fruit contain latex, harvesting fruit at full maturity is critical to quality. Judging maturity in sapodilla is extremely difficult. Even within a single cluster, fruit maturity may vary greatly, although fruits generally mature from flowers produced at the base of the cluster to the tip. Sundararajan and Rao (1967) suggest using total soluble solids as a measure of maturity in sapodilla, although the variation in fruit age within a tree may require that each fruit is judged individually for maturity. Abdul-Karim et al. (1987) found that fruit length and width were better indicators of maturity than weight and volume, or firmness. Some varieties of sapodilla maintain the remnants of the flower style until maturity (George 1982), which may also be a good indicator. Ripeness can occur anywhere from 9 to 13 days after harvest (Lakshminarayana and Subramanyam 1966).

Sapodilla fruit is most commonly consumed fresh, when fully ripe. It is primarily a dessert fruit in most areas. Flavor of the ripe fruit is improved by chilling just prior to eating. Sapodilla fruit is also used for making ice cream, but is not typically used for jam or canning. The fruit is also eaten as a dried fruit in India.

POSTHARVEST STORAGE

Sapodilla respiration pattern follows that of a climacteric fruit (Broughton and Wong 1979; Selvaraj and Pal 1984; Abdul-Karim et al. 1987; Brown and Wong 1987). Respiration may be slowed by growth retardants such as gibberellic acid (GA), kinetin and silver nitrate (Gautam and Chundawat 1990b).

Sapodilla may be stored under controlled conditions for a short period of time. Singh and Mathur (1954) found that optimum cold storage was obtained at 35° to 38°F with a relative humidity of 85%-90%. Under these conditions, fruit could be stored for up to eight weeks. Broughton and Wong (1979) found that holding the fruit at 4°C before storing at 20°C extended the storage life of the fruit although exposure to 4°C for longer than ten days resulted in chilling injury. Storage of sapodilla under high CO2 concentrations, provided CO2 was less than 20% (v/v), and low ethylene concentrations, also prolonged the storage life of the fruit. Upon reaching full maturity, sapodilla fruit deteriorates rapidly, lasting only 2 to 10 days (Brown and Wong 1987).

Gautam and Chundawat (1990a) examined the effects of various growth retardants on postharvest changes in sapodilla. Application of GA, kinetin, and silver nitrate resulted in up to a two-day increase in storage time due to reduction of catalase and pectin methyl esterase activity, and reductions in respiratory activity and ethylene production. The application of these compounds appears to reduce the rate at which fruit ripens as well as affecting fruit quality characteristics such as total sugars, acidity, ascorbic acid, and starch (Gautam and Chundawat 1990b).

Gibberellic acid prolongs the time which sapodilla fruit can be stored before rot occurs, as well as prolonging fruit softness and fruit skin shrinkage (Kumbhar and Desai 1986). Gautam and Chundawat (1990a, b) used a 300 ppm GA solution, although Kumbhar and Desai (1986) found a 75 ppm solution to be the most effective in a range of concentrations from 75 to 225 ppm.

Both wax coating and 2,4-Dichloro-phenoxy acetic acid (2,4-D ) have been shown to retard the ripening process in sapodilla, while 2-Chloroethyl phosphonic acid (ethrel) (Ingle et al. 1981; Suryanarayana and Goud 1984) and ethylene (Sastry 1970) greatly accelerate ripening. Polyethylene bags can also reduce weight loss in sapodilla by about 50% (Kumbhar and Desai 1986).

Because of the high moisture and nutrient content of the fruit, sapodilla is especially prone to postharvest diseases. Common diseases include sour rot (Geotrichum candidum), Cladosporum rot (Cladosporum oxysporium), and blue mold rot (Penicillium italicum). Bakar and Abdul-Karim (1994) found benlate (methyl-N-1-butylcarbomoyl), a commonly used fungicide for postharvest treatment of sapodilla, to best control both fungal and bacterial pathogens of sapodilla. Although several non-chemical treatments have been tested, none have proven to be successful against postharvest pathogens of sapodilla.

CULTIVARS

A number of sapodilla cultivars are available at nurseries in the United States specializing in tropical fruit species (Table 1). Because of the lack of information in the literature on many of the cultivars, the table is incomplete. 'Prolific' appears to be the best producer in Florida. It is extremely precocious and produces fruit of good flavor. Grafted trees bear fruit within 3 to 5 years of planting in Florida and mature trees may bear 150 to 225 kg of fruit. The fruit is easily damaged and is therefore susceptible to some postharvest diseases. Another successful variety in Florida is 'Brown Sugar'. As its name implies, the fruit is very sweet, with a slightly granular flesh. Trees bear crops 3 to 5 years following planting, with mature trees bearing crops of 125 to 200 kg. In Florida, 'Tikal' fruits up to four months earlier than other sapodilla cultivars (Campbell et al. 1987). Many cloned Florida cultivars have proven to be unfruitful in successive years. Some examples include 'Martin','Adelaide', and 'Seedless'.

'Kalipatti' is the most planted cultivar in the Gujarat region of India, accounting for about 99% of the acreage there. It also appears to be the highest yielding cultivar of those tested in India (Chundawat and Bhuva 1982) and, therefore, will likely continue to be the most widely planted. Average yields are 160 kg per tree, with fruit of medium size and low seed count. 'Russel' was considered to be the best variety in a five-year Puerto Rico study.

The major obstacle to sapodilla producers appears to be opening foreign markets. At present, most sapodilla production is limited to local consumption regardless of where the fruit is produced. Past attempts at establishing a European market have failed (Chadha 1992), and the future of sapodilla is uncertain.

REFERENCES


Table 1. Description of some named cultivars of sapodilla.

Cultivar Origin Fruit size (g) Yield/tree Location Reference
Addley Bahamas Very poor Florida Campbell and Malo 1973
Adelaide Bahamas 150 kg Venezuela Avilan et al. 1980
Badam 45 India Sundarajan and Rao 1967
Baramasi 118 India Sundarajan and Rao 1967
Big Pine Key Florida Very poor Florida Campbell and Malo 1973
Black Florida Very poor Florida Campbell and Malo 1973
Brown Sugar Florida 133-170 901 fruit Venezuela Avilan et al. 1980
Brown Sugar 125-200 kg Florida Campbell and Malo 1973
Calcutta Round 98 India Sundarajan and Rao 1967
Cricket Ball 142 93 kg India Chundawat and Bhuva 1982
Dwarapudi 90 India Sundarajan and Rao 1967
Gavarayya 112 India Sundarajan and Rao 1967
Guthi 56 India Sundarajan and Rao 1967
Jamaica No. 4 Jamaica Very poor Florida Campbell and Malo 1973
Jamaica No. 5 Jamaica Very poor Florida Campbell and Malo 1973
Jantung Malaysia 100 Malaysia Abdul-Karim et al. 1987
Kalipatti 98 160 kg India Chundawat and Bhuva 1982
Kirtabarti 84 India Sundarajan and Rao 1967
Long Oval 140 India Sundarajan and Rao 1967
Martin Florida Very poor Florida Campbell and Malo 1973
Modello Florida 227-340 50-100 kg Florida Campbell and Malo 1973
Mohangottee 102 107 kg India Chundawat and Bhuva 1982
Oval 84 India Sundarajan and Rao 1967
Pala 31 India Sundarajan and Rao 1967
Pilipatti 82 115 kg India Chundawat and Bhuva 1982
Prolific Florida 170-225 520 fruit Venezuela Avilan et al. 1980
Prolific 150-225 kg Florida Campbell and Malo 1973
Russell Florida 284-454 544 fruit Venezuela Avilan et al. 1980
Russell 25-100 kg Florida Campbell and Malo 1973
Saunders Florida Very poor Florida Campbell and Malo 1973
Seedless Florida small <12.5 kg Florida Campbell and Malo 1973
Tagarampudi 84 India Sundarajan and Rao 1967
Tikal Mexico 113-170 170-225 kg Florida Campbell and Malo 1973
Tikal 120 150-175 kg Florida Campbell et al. 1987
Vavivalasa 98 India Sundarajan and Rao 1967
Zumakhia 57 55 kg India Chundawat and Bhuva 1982


Last update June 23, 1997 aw