Nitrogen fixation - symbiotic relationship with members of the bacterial genus Rhizobium Atmospheric N2 + energy ---->NH3---->amino acids ---->proteins.
Other sources of nitrogen are NO3 and urea

Legumes incorporate more protein than other plants, possibly because N is not limiting.

However, legumes are deficient in isoleucine, lysine and S-containing a.a.'s. Certain grass grain - legume combinations provide a balanced amino acid composition.

Legumes used for direct consumption
I. Pulses
peas
lentils
broad beans
chick-peas
soybeans
pigeon peas
black-eyed peas
lima beans
common bean
peanuts

II. Others
tamarind - pulp used in flavoring in sauces
carob - seeds used to make a coffee-like beverage

Forage legumes
alfalfas
clovers
lespedezas
sweet clover
bird's foot trefoil

Peanuts (groundnuts) - Arachis hypogaea - rich in oil and protein, grown mostly for oil

Origin in South America, probably Peru, 4000-5000 years old but probably much older. Plants are allotetraploids.

All species of Arachis are (40-70) are geocarpic. After fertilization, pedicels curve downward and developing fruit is pushed into soil.

Breeding via experimental crossing is difficult due to strict inbreeding in some lines (interspecific sterility barriers inhibit the incorporation of large amounts of genetic variability found in nature.

Pigeon Pea - Cajanus cajan - grown on poor land by small farmers, most of world crop is grown in India. Pea in split-pea soup

Origin possibly in India. Supposedly a lot of potential for development of high-yielding cultivars but not much being done, presumably due to lack of demand.

Chick pea (Garbanzo) Cicer arietinum- used as a grain, 79% is grown in India, a basic component of diet, considered a poor man's food.

Earliest records are from Turkey about 7400 ybp.

Efforts to increase productivity have been relatively unsuccessful. Do not respond to fertilization with higher productivity.

Soybeans - Glycine max - most important grain legume

Uses in Far East are mainly for human consumption - "poor man's meat"

Liquid
Powder
Curd
Immature plants (sprouts)

Uses in West are:

Oil - margarine, shortening, mayonnaise, salad oils and dressing
Meal - feed for pigs and chickens

Soybeans are processed to produce curd, cheese, drinks and sauces.

Dried beans are crushed in water, heated; liquid decanted off is soy milk - basis for nondairy infant formulas in U.S. Solid portion left is okata - cottage cheese like. Tofu is made from soy milk via a curdling process. Tofu is flavorless but has a good texture and is used as a meat substitute. Soy sauce is made from okara via a process involving fungi and salt water.

Origin in northeastern China, germ plasm base is being destroyed.

Only recently became popular in West and U.S. is currently largest producer of soybeans, little is used directly in U.S. but texturized vegetable protein (TVP) may change that. Henry Ford had an obsession with soybeans and wore a suit made of soy fabric.

Lentils - Lens culinaris - grain legume grown in areas of wheat and barley cultivation in Meditteranean. High protein content and important meat substitute in many peasant communities.

Origin in Middle East 8000-9000 y.b.p.

Drought resistant but yields are low.

Peas - Pisum sativum - One of 4 most important pulses and an important source of protein

Origin probably in Mediterranean about 9000 y.b.p.

Grown in cool regions or as a winter crop in hot regions. Dry mature peas of immature pods are used for human food.

Broad bean - Vicia fabia - Large seeds with high protein content, among first crops cultivated

Origin in Mediterranean

Grown in cool regions of North America. Aggravates genetic disorder found in people of Med. origin FAVISM ----> hemolytic anemia (breakdown of red blood cells) Presence of this gene(s) in humans provided resistance from malaria.

Cowpeas (Black-eyed peas)- Vigna unguiculata - Source of protein (seeds) in semi-arid Africa and Asia, remainder of plant is fed to livestock. Not important in world trade.

Origin in Ethiopia 5-6000 y.b.p.

Popular in American South - Hoppin' John - rice + black-eyed peas + salt pork, eaten before noon on New Year's day for good luck.

Common bean - Phaseolus vulgaris - kidney, navy, pinto, black, green, string, wax, snap, among others, 2nd most important after soybeans.

Origin - Central and South America about 3000 y.b.p. Historically grown with corn, wild plants are vines and corn was used as a prop for vines. Nitrogen fixation helped corn.

Lima beans - Phaseolus lunatus - close relative of common bean, used mainly in dry form

Origin in Central America 7-10,000 y.b.p.

some cultivars contain cyanogenic compounds ----> cyanide

FORAGE CROPS - Hay production, grazing, green manure, alfalfa and clovers are most important

Alfalfa - Medicago sativa

Bird's foot trefoil - Lotus corniculatus - recently popular in N.E. U.S.

Clovers - Trifolium

Lespedezas - Lespedeza

Sweet clover - Melilotus - good soil improver

There are several advantages of grass-legume associations:

1. soil enrichment
2. balanced diet for livestock.

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