The cultivated forms were formerly called var latifolius. This was recently recognized as an obsolete synonym of var acutifolius (formerly considered to be a wild form of the species). This means that this variety comprises both wild and cultivated populations[].

Common Name: Tepary Bean

General Information

Phaseolus acutifolius is a herbaceous, annual plant growing from a fibrous rootstock. It produces weak stems that either trail over the ground or twine around other plants for support[]. The plants vary widely in height according to cultivar, with dwarf forms only 30cm tall and large forms up to 4 metres tall[, , ].
The plant is grown mainly for its edible seed and is said to have been in cultivation for over 5,000 years in southwestern N. America[]. Nowadays it is grown mainly in south-western USA and Mexico as a traditional pulse crop, though it is also cultivated, mostly on a small scale, in further parts of USA; Central America; the West Indies; Chile; Australia; S Asia; E and W Africa (Uganda, Mali, Senegal)[]. After World War II the cultivation decreased drastically in the traditional areas, the crop however is nowadays once more gaining interest[].

Known Hazards

The seed contains various antinutritional factors, such as trypsin inhibitors, flatulent oligosaccharides and phytic acid[]. The lectin activity is exceptionally high, but is readily reduced by cooking; whereas cyanogenic glucosides have not been detected[].
Consumption of raw tepary bean flour has been recorded to cause death in mice and rats within 3 - 4 days, but soaking and cooking the seeds eliminated toxicity completely[].

Botanical References

Range

Central America - ?Guatemala; Southwest N. America - southern Mexico north to Arizona, New Mexico and Texas.

Habitat

Usually found growing along srream beds and dry washes in pine-oak forest, scattered among small bushes and cacti[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual Climber
Height	2.00 m
Pollinators	Insects, Self
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Phaseolus acutifolius is a plant mainly of the drier subtropics, though it can also be grown in tropical areas at elevations up to 1,900 metres so long as the climate is not excessively wet[]. It prefers a mean annual temperature within the range 20 - 30°c, but can tolerate 8 - 38°c[] It cannot be grown in areas where night temperatures fall below 8°c[]. It prefers a mean annual rainfall of 600 - 1,000mm, tolerating 300 - 1,700mm[]. Excessive rainfall may create vegetative growth at the expense of seed yield[]. The plant can withstand heat and a dry atmosphere, though only very few varieties are suited for the wet tropics[].
Requires a sunny position[]. Succeeds in most soils that are well-drained[]. Succeeds in poor, shallow soils[]. Established plants are rather drought resistant[].Prefers a pH in the range 6 - 7, but tolerates 5 - 8[].
The crop can be grown on residual soil moisture[].
Often cultivated for its edible seed, there are many cultivated forms with seeds considerably larger than the wild forms[]
The species is highly daylength sensitive, growmg under natural field conditions during the long days of summer and beginning to bloom in late summer when daylength has fallen to around 13 hours[].
Flowering occurs within 27 - 40 days from germination[].
First harvest may be taken in as little as 60 days in the tropics, though in cooler climates it can be up to 120 days from sowing[].
The seeds of many domesticated types of tepary bean are shattered less easily than those of wild types[].
Average yields of dry seed under dry conditions are reported to be 450 - 800 kg/ha and with irrigation 0.9-1.7 t/ha[].
In areas of poor rainfall, tepary bean has possibilities as a catch-crop where a rapid food supply is needed[].
This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Mature seeds - dried[, ]. They are used as dry shell beans to make soups[, ]. They are also ground into a flour; fried; parched; or processed into a meal for commercial use[]. Tepary beans have a strong flavour and odour and are less palatable than common beans[]. The seedpods are 40 - 100mm long, 5 - 13mm wide and 4 - 8mm thick, containing 2 - 9 oblong to rounded seeds 4 - 10mm long, 4 - 7mm wide and 2 - 5mm thick[, ]. On storage, the dry seeds become very hard and take a very long time to cook[]. Cultivars with white seeds have a more permeable seedcoat than cultivars with black seeds, resulting in a shorter cooking time[].

The young, green seedpods are occasionally eaten[].

The seeds can be sprouted and then eaten cooked or in salads[].

The leaves are considered edible in parts of Africa, but they are tougher than those of common bean (Phaseolus vulgaris) and take longer to cook[].

Medicinal

The plant is bitten and held between the teeth as a traditional treatment for toothache[].

Agroforestry Uses:

Tepary bean has occasionally been grown as a green manure, e.g. in the United States[]. It may also be used as a cover crop and an intercrop in agroforestry systems[].

Other Uses

None known

Propagation

The seed of cultivated forms absorbs water easily; in moist soils the testa wrinkles within 5 minutes, whilst when soaked in water the testa wrinkles in 3 minutes[]. This leads to quick and even germination[]. The rate of germination increases with increasing temperatures from 10 - 35°c[].
Seedling emergence is faster in white-seeded than in dark-seeded types[].
The seed of wild forms usually has a hard seedcoat and will benefit from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing.
The seeds of domesticated types have no dormancy, which is a disadvantage in humid regions, where fallen seeds will germinate rapidly[].

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