Inga edulis, known as ice-cream bean, joaquiniquil, cuaniquil (both from Nahuatl: cuahuxinicuile combining cuahuitl "tree"; icxitl "feet" and necuilli "crooked"[Duke (1983)] The taxonomic genus name Inga is derived from its name with the Tupí people of South America ( ingá
Biology
Mature trees of
I. edulis reach 30 m (98 ft) high and 60 cm (2.0 ft) diameter at breast height, usually branching from below 3 m (9.8 ft). The branches form a broad, flat, moderately dense canopy.
I. edulis can be evergreen in tropical regions or deciduous when planted in colder regions. The tree has a pale grey-coloured trunk. The stems and young twigs can be sparsely to densely haired. The leaves are alternate, evenly
pinnate, 10–30 cm long, with four to six pairs of opposite, dark-green, membranous, slightly pubescent, oval leaflets. The terminal leaflets can grow up to 18 cm long by 11 cm wide in comparison to the basal ones. Extrafloral
nectaries are placed on petioles, and
can be either inconspicuous, absent, or caducous.
The flowers are fragrant, sessile, and pentamerous, and are arranged in dense axillary spikes. Each flower has a calyx tube with five puberulent, striated lobes, and a corolla with five silky, villous petals. These are around 14–20 mm long and contain numerous white . The fruits are longitudinally ribbed, cylindrical, indehiscent, leguminous pods, which can be straight, curved, or often spirally twisted up. They are pendant and up to 1 m long and yellowish brown to green in colour. The number of purplish-black to olive-colored ovoid seeds can vary from 10 to 20. These are embedded in the sweet, cottony, white arillus, which gives it the name ice-cream bean, since their texture and sweetnes are reminiscent of ice cream.
Symbiosis
Inga species are symbiotic with ants (e.g.,
Pheidole species), which feed on the nectar of the extrafloral nectaries. In exchange, the ants patrol over the
Inga plant to protect it against
. Certain insects, such as
Riodinidae caterpillars, excrete sugary honeydew from their tentacle nectaries. The ants form a symbiosis with the caterpillars by letting them feed on the tree in exchange for their sugary honeydew.
The inga plant can also form symbiotic relationships in which nitrogen gas can be fixated by bacteria and mycorrhiza, as can other legumes. Surveys have shown that I. edulis forms a mutualistic relationship with Bradyrhizobium bacteria.
Synonyms
This plant has a convoluted history of synonymy with
Inga vera. The plants discussed under that name by Brenan and Kunth are actually
I. edulis, whereas that based on the writings of Carl Ludwig Willdenow refers to the actual
I. vera.
Inga edulis in works referring back to authorities other than von Martius usually refers to
Inga feuilleei.
[ILDIS (2005)]
Synonyms of Inga edulis Mart.:
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Feuilleea edulis (Mart.) Kuntze
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Inga benthamiana Carl Meissner
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Inga edulis var. grenadensis Urb.
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Inga minutula (Schery) T.S.Elias
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Inga scabriuscula Benth.
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Inga vera Kunth
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Inga vera sensu Brenan
-
Inga ynga (Vell.) J.W.Moore
-
Mimosa inga L.
-
Mimosa ynga Vell.
[USDA (2007)]
Ecology
The natural distribution of
I. edulis spreads from
Central America to South America, and ranges from subtropical dry to tropical wet conditions.
It can be found at elevations from sea level up to 2200 m.
I. edulis grows best when mean annual daytime temperatures range from 23 to 30 °C. However, it can tolerate 18–35 °C. During the resting period, mature trees can survive −2 °C, while young plants are killed at 0 °C. Preferred
precipitation ranges from 1200 to 2500 mm but 640 to 4000 mm of annual precipitation can be tolerated, also. It can be grown on a widely varying range of soil conditions. It prefers a
soil pH of 5.0–6.5, but can also grow in very strongly acidic soil down to a pH of 4.5 or moderately alkaline conditions up to pH 8.0.
The natural habitat includes margins of large rivers like the
Amazon River, thickets below high water line, and wooded swamps.
The tree can tolerate temporarily waterlogged soils for 2–3 months each year, but it can also tolerate drought seasons up to 6 months.
Furthermore,
I. edulis can cope with heavy soils or slope fairly well.
In terms of soil fertility,
I. edulis is not only unpretentious, but also has the potential to improve
soil quality. As a
Fabaceae, this species can compensate for nutrient-depleted soils by fixing nitrogen with its root nodules. Ammonium and nitrate salts found in soil typically result in nodulation reduction.
I. edulis is an exception, as its nodules increase in size when ammonium ion levels are at 5mM. Nitrate, though, did not benefit
I. edulis and continued to show properties that prevented nodulation. Additionally to nitrogen,
I. edulis is reported to significantly increase the extractable
phosphorus content in the soil, thus further ameliorates degraded soils.
Cultivation
I. edulis is widely cultivated in
agroforestry systems in its neotropical dispersal area. This form of cultivation, often associated with
Coffea or
Theobroma cacao culture, is widely known since pre-Columbian times.
of
I. edulis seeds is fairly easy, as the seeds are recalcitrant and often germinate already in the pod. Seeds lose their ability to germinate, though, after two weeks of storage.
Direct sowing of the seeds is possible, but the establishment of seedlings with already a certain height can decrease competition with noxious weeds, thus increasing growth.
Further, the inoculation with
rhizobia and
fungi in depleted soils is recommended to promote growth.
These inoculi can easily be produced by collecting soil, nodules, and fine roots from mature, nodulated
I. edulis stands.
This species seems to be very resistant to pests and diseases. Minor damage can result from fungal attacks in the seedling stage. Mature
I. edulis can be defoliated by
Lepidoptera larvae. Also, fruit fly larvae often damage the seed testa. In
Ecuador,
I. edulis is specially susceptible to
mistletoe infestations.
Uses
Food crop
I. edulis has been cultivated as a fruit tree for millennia, and is widely sold on the local South American marketplace, mainly for the sweet, succulent pulp surrounding the seeds. The white pulp (aril) is consumed raw as a sweet snack, though it is less nutritious than the seeds. Toxic compounds such as trypsin and chymotrypsin inhibitors contained in the seeds of I. edulis are destroyed through cooking.
In Colombia, the arils are also used to prepare an alcoholic drink called cachiri for a festival of the same name. The native women chew the arils and spit the mixture into a vat, where it is left to ferment.
Use in agroforestry systems
Due to its rapid growth and ability to improve soil properties,
I. edulis has found widespread use in tropical
agroforestry. Most notably, inga alley cropping is used as an alternative to slash-and-burn cultivation. It is also a popular shade tree for
coffee,
Cocoa bean, and
tea plantations. One important reason for this is that in comparison to other
shade tree species,
I. edulis retains its leaves in the dry season.
Cuttings and leaves also used as mulch and animal fodder.
The wood is sometimes used as timber and for fuel; its popularity as a source of firewood stems from its high caloric value and weak smoke production.
Despite its rapid growth and significant potential to improve soils in agroforestry systems, I. edulis has not been the object of any improved breeding programs.
Medicinal uses
I. edulis is widely used in native South American folk medicine.
Decoctions of the leaves, bark, or root commonly are used as treatments for diarrhea, arthritis, and rheumatism.
Crushed, boiled leaves are ingested to relieve coughing or applied to lip sores, possibly caused by
herpes.
Several studies have investigated
I. edulis as a source of
polyphenols for use as
and have shown promising results.
.
Further reading
Ice Cream Beans
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Duke, James A. (1983): Inga edulis Mart. Crop Fact Sheet. Version of 07-JAN-1998. Retrieved 2007-DEC-17.
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International Legume Database and Information Service (ILDIS) (2005): Genus Canavalia. Version 10.01, November 2005. Retrieved 2007-DEC-17.
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United States Department of Agriculture (USDA) (2007): Germplasm Resources Information Network – Inga edulis. Retrieved 2007-DEC-18.
