A legume () is a plant in the family Fabaceae
(or Leguminosae), or the fruit or seed of such a plant (also called a pulse, especially
in the mature, dry condition). Legumes are grown agriculturally, primarily
for human consumption, for livestock forage and silage, and as soil-enhancing green manure. Well-known legumes include alfalfa, clover,
beans, peas, chickpeas, lentils, lupins, mesquite, carob, soybeans, peanuts, and tamarind. Legumes produce a botanically unique type
of fruit – a simple dry fruit that develops from a simple carpel and usually dehisces
(opens along a seam) on two sides. A common name for this type of fruit is a
pod, although the term “pod” is also applied to a number of other fruit types, such as
that of vanilla (a capsule) and of the radish (a silique). Legumes are notable in that most of them have
symbiotic nitrogen-fixing bacteria in structures called root nodules. For that reason, they play a key role in crop
rotation.==Terminology==The term pulse, as used by the United Nations’
Food and Agriculture Organization (FAO), is reserved for legume crops harvested solely
for the dry seed. This excludes green beans and green peas,
which are considered vegetable crops. Also excluded are seeds that are mainly grown
for oil extraction (oilseeds like soybeans and peanuts), and seeds which are used exclusively
for sowing forage (clovers, alfalfa). However, in common usage, these distinctions
are not always clearly made, and many of the varieties used for dried pulses are also used
for green vegetables, with their beans in pods while young. Some Fabaceae, such as Scotch broom and other
Genisteae, are leguminous but are usually not called legumes by farmers, who tend to
restrict that term to food crops.==Uses==
Farmed legumes can belong to many agricultural classes, including forage, grain, blooms,
pharmaceutical/industrial, fallow/green manure, and timber species. Most commercially farmed species fill two
or more roles simultaneously, depending upon their degree of maturity when harvested.==Human consumption==Grain legumes are cultivated for their seeds,
which are used for human and animal consumption or for the production of oils for industrial
uses. Grain legumes include beans, lentils, lupins,
peas, and peanuts.===Nutritional value===
Legumes are a significant source of protein, dietary fiber, carbohydrates and dietary minerals;
for example, a 100 gram serving of cooked chickpeas contains 18 percent of the Daily
Value (DV) for protein, 30 percent DV for dietary fiber, 43 percent DV for folate and
52 percent DV for manganese. Like other plant-based foods, pulses contain
no cholesterol and little fat or sodium.Legumes are also an excellent source of resistant
starch which is broken down by bacteria in the large intestine to produce short-chain
fatty acids (such as butyrate) used by intestinal cells for food energy.Preliminary studies
in humans include the potential for regular consumption of legumes in a plant-based diet
to reduce the prevalence or risk of developing metabolic syndrome. There is evidence that a portion of pulses
(roughly one cup daily) in a diet may help lower blood pressure and reduce LDL cholesterol
levels, though there is a concern about the quality of the supporting data.===Classification of pulses===FAO recognizes 11 primary pulses. The FAO notes that the term “pulses” is limited
to legumes harvested solely for dry grain, thereby excluding legumes that are harvested
green for food (green peas, green beans, etc.) which are classified as vegetable crops. Also excluded are those legumes used mainly
for oil extraction (e.g., soybeans and groundnuts) or used exclusively for sowing purposes (e.g.,
seeds of clover and alfalfa). Dry beans (FAOSTAT code 0176, Phaseolus spp.
including several species now in Vigna) Kidney bean, navy bean, pinto bean, black
turtle bean, haricot bean (Phaseolus vulgaris) Lima bean, butter bean (Phaseolus lunatus)
Adzuki bean, azuki bean (Vigna angularis) Mung bean, golden gram, green gram (Vigna
radiata) Black gram, urad (Vigna mungo)
Scarlet runner bean (Phaseolus coccineus) Ricebean (Vigna umbellata)
Moth bean (Vigna aconitifolia) Tepary bean (Phaseolus acutifolius)
Dry broad beans (code 0181, Vicia faba) Horse bean (Vicia faba equina)
Broad bean (Vicia faba) Field bean (Vicia faba)
Dry peas (code 0187, Pisum spp.) Garden pea (Pisum sativum var. sativum)
Protein pea (Pisum sativum var. arvense) Chickpea, garbanzo, Bengal gram (code 0191,
Cicer arietinum) Dry cowpea, black-eyed pea, blackeye bean
(code 0195, Vigna unguiculata ) Pigeon pea, Arhar/Toor, cajan pea, Congo bean,
gandules (code 0197Cajanus cajan) Lentil (code 0201, Lens culinaris)
Bambara groundnut, earth pea (code 0203, Vigna subterranea)
Vetch, common vetch (code 0205, Vicia sativa) Lupins (code 0210, Lupinus spp.)
Pulses NES (code 0211), Minor pulses, including: Lablab, hyacinth bean (Lablab purpureus)
Jack bean (Canavalia ensiformis), sword bean (Canavalia gladiata)
Winged bean (Psophocarpus tetragonolobus) Velvet bean, cowitch (Mucuna pruriens var.
utilis) Yam bean (Pachyrhizus erosus)==Forage==Forage legumes are of two broad types. Some, like alfalfa, clover, vetch (Vicia),
stylo (Stylosanthes), or Arachis, are sown in pasture and grazed by livestock. Other forage legumes such as Leucaena or Albizia
are woody shrub or tree species that are either broken down by livestock or regularly cut
by humans to provide livestock feed. Legumes base feed fed to animals improves
animal performance compared to diets of perennial grass diet. Factors that attribute towards such result:
larger consumption, quicker rate of digestion and feed conversion rate efficiency.==Other uses==Legume species grown for their flowers include
lupins, which are farmed commercially for their blooms as well as being popular in gardens
worldwide. Industrially farmed legumes include Indigofera
and Acacia species, which are cultivated for dye and natural gum production, respectively. Fallow/green manure legume species are cultivated
to be tilled back into the soil in order to exploit the high levels of captured atmospheric
nitrogen found in the roots of most legumes. Numerous legumes farmed for this purpose include
Leucaena, Cyamopsis, and Sesbania species. Various legume species are farmed for timber
production worldwide, including numerous Acacia species and Castanospermum australe. Legume trees like the locust trees (Gleditsia,
Robinia) or the Kentucky coffeetree (Gymnocladus dioicus) can be used in permaculture food
forests. Other legume trees like laburnum and the woody
climbing vine wisteria are poisonous.==Nitrogen fixation==Many legumes contain symbiotic bacteria called
Rhizobia within root nodules of their root systems. (Plants belonging to the genus Styphnolobium
are one exception to this rule.) These bacteria have the special ability of
fixing nitrogen from atmospheric, molecular nitrogen (N2) into ammonia (NH3). The chemical reaction is: N2 + 8H+ + 8e− → 2NH3 + H2Ammonia is then
converted to another form, ammonium (NH+4), usable by (some) plants by the following reaction: NH3 + H+ → NH+4This arrangement means that
the root nodules are sources of nitrogen for legumes, making them relatively rich in plant
proteins. All proteins contain nitrogenous amino acids. Nitrogen is therefore a necessary ingredient
in the production of proteins. Hence, legumes are among the best sources
of plant protein. When a legume plant dies in the field, for
example following the harvest, all of its remaining nitrogen, incorporated into amino
acids inside the remaining plant parts, is released back into the soil. In the soil, the amino acids are converted
to nitrate (NO−3), making the nitrogen available to other plants, thereby serving as fertilizer
for future crops. In many traditional and organic farming practices,
crop rotation involving legumes is common. By alternating between legumes and non-legumes,
sometimes planting non-legumes two times in a row and then a legume, the field usually
receives a sufficient amount of nitrogenous compounds to produce a good result, even when
the crop is non-leguminous. Legumes are sometimes referred to as “green
manure”. Sri Lanka developed the farming practice known
as coconut-soybean intercropping. Grain legumes are grown in coconut (Cocos
nuficera) groves in two ways: intercropping or as a cash crop. These are grown mainly for their protein,
vegetable oil and ability to uphold soil fertility. However, continuous cropping after 3–4 years
decrease grain yields significantly.==Farming system==
The type of crop(s) grown or animal rearing will be dependent on the farming system, either
vegetables, tubers, grains, cattle etc. In cattle rearing, legume trees such as Gliricidia
sepium can be planted along edges of field to provide shade for cattle, the leaves and
bark are often eaten by cattle. Green manure can also be grown between periods
when crops of economic importance are harvested prior to the next crops to be planted.==History==
Archaeologists have discovered traces of pulse production around Ravi River (Punjab), the
seat of the Indus Valley Civilisation, dating to c. 3300 BCE. Meanwhile, evidence of lentil cultivation
has also been found in Egyptian pyramids and cuneiform recipes. Dry pea seeds have been discovered in a Swiss
village that are believed to date back to the Stone Age. Archaeological evidence suggests that these
peas must have been grown in the eastern Mediterranean and Mesopotamian regions at least 5,000 years
ago and in Britain as early as the 11th century. But one particular bean has become the leading
legume planted worldwide, the soybean. It was first domesticated around 11000 BC
in China, a descendant of the wilde vine Glycine soja. Domesticated soybean was introduced to the
USA (Philadelphia) by Benjamin Franklin from France in 1804. Henry Ford, a vegetarian, was the first person
to use soybeans for large-scale industrial purposes. Concentrating on his company, from 1932 to
1933 he invested over 1 million dollars in research on soybeans. Prior to WWII, 40% of cooking oil was imported
into the US. When the war came, supply routes were disrupted,
which encouraged the soybean culture in the US. Due to the years of research done by Henry
Ford, the domestic soybean oil industry was born. Between 1970 and 1976, soybean production
increased approximately 30%. Oil yield from bulk soybeans averages about
18%. Its modern day usage ranges from margarine,salad
oils, shortening and the previously mentioned cooking oil.==Distribution and production==
Legumes are widely distributed as the third-largest land plant family in terms of number of species,
behind only the Orchidaceae and Asteraceae, with about 751 genera and some 19,000 known
species, constituting about seven percent of flowering plant species.In 2017, India
was the largest producer of pulses with 23% of the world total (table). Other major producers were Poland, the United
Kingdom, and Mozambique.===Storage of grain legumes===
Seed viability decreases with longer storage time. Studies done on Vetch, Horse beans, and peas
show that they last about 5 years in storage. Environmental factors that are important in
influencing germination are relative humidity and temperature. Two rules apply to moisture content between
5 and 14 percent: the life of the seed will last longer if the storage temperature is
reduced by 5 degree celsius. Secondly, the storage moisture content will
decrease if temperature is reduced by 1 degree celsius.==Pests of legumes==
A common pest of grain legumes that is noticed in the tropical and subtropical Asia, Africa,
Australia and Oceania are miniscule flies that belong to the family Agromyzidae, dubbed
“bean flies”. They are considered to be the most destructive. The host range of these flies is very wide
amongst cultivated legumes. Infestation of plants starts from germination
through to harvest, and they can destroy an entire crop in early stage. Black bean aphids are a serious pest to broad
beans and other beans. Common host for this pest are fathen, thistle
and dock. Pea and Bean Weevil: damages by these two
culprits are characterised by leaf margins having semi-circular notches. Stem Nematode: there are many different Nematodes;
they are very widespread but will be found more frequently in areas where host plants
are grown.==Common diseases of legumes==
Anthracnose, caused by Colletotrichum trifolii, Common leaf spot caused by Pseudomonas syringae
pv. syringae, Crown wart caused by Physoderma alfalfae, Downy mildew caused by Peronospora
trifoliorum, Fusarium root rot caused by Fusarium spp, Rust caused by Uromyces striatus, Sclerotina
Crown and stem rot caused by Sclerotinia trifoliorum, Southern blight caused by Sclertium rolfsii
, Pythium root rot (browning root rot) caused by Pythium spp, Fusarium wilt caused by Fusarium
oxysporum, Root knot, agent Meloidogyne hapla. These are all classified as Biotic problems.Abiotic
Problems: Nutrient deficiency(ies) (nitrogen, phosphorus, potassium, copper, magnesium,
manganese, boron, zinc), pollutants (air, water, soil, pesticide injury, fertilizer
burn), toxic concentration of minerals, and unfavorable growth conditions.==Principles applied to control diseases
in plants==There are three main factors that contribute
to the success of any plant disease: it must have a host (susceptible plants), the right
environment, and a pathogen. With any one of the three factors being eliminated
there will be no disease.To help achieve this, different approaches can be taken to mitigate
its severity before it’s too late. Control, diseases in plants should be kept
below severity line at which it may be of economical importance, one can reduce the
inoculum or slow the rate of its increase in plants. There are some principles that are etiological
to control plant diseases: exclusion,eradication,therapy and resistant variety.==Pollination of legumes==
Legumes can either be self-pollinated or cross-pollinated. Pollination serves the purpose for the continuation
of the species and its genetic materials to its offspring. Self-pollination limits the capability for
genetic variation, whereas for cross-pollination the opposite is true. Some tropical legumes that are closely self-pollinated
are: Macroptilium atropurpureum ‘Siratro’, Macroptilum lathyroides, Centrosema pubescens,
Neonotonia wightii, and Lotononis bainesii. However, the autogamous annual Stylosanthes
humilis proved otherwise by adapting in response to changing conditions during an experiment,
and was found to be composed of several genotypes showing heterogeneity. Two legumes used for pasture with cross-pollination
are: Desmodium intortum and Desmodium uncinatum. When the flower is opened, this is the only
time fertilization will take place. These two species’ characteristics vary in
morphology and ruggedness.==International Year of Pulses==The International Year of Pulses 2016 (IYP
2016) was declared by the Sixty-eighth session of the United Nations General Assembly. The Food and Agriculture Organization of the
United Nations was nominated to facilitate the implementation of IYP 2016 in collaboration
with governments, relevant organizations, non-governmental organizations and other relevant
stakeholders. Its aim was to heighten public awareness of
the nutritional benefits of pulses as part of sustainable food production aimed towards
food security and nutrition. IYP 2016 created an opportunity to encourage
connections throughout the food chain that would better use pulse-based proteins, further
global production of pulses, better use crop rotations and address challenges in the global
trade of pulses.==See also==
List of dried foods List of legume dishes
Peanut allergy