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CSS 330 World Food Crops
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Week 5 (unit 10)

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Soybeans, Groundnuts & Dry Beans

Leguminous food crops
Origin, taxonomy, and genetic systems
Growth requirements, physiological and adaptive traits
Production statistics, economics and marketing
Quality factors, end-uses

Dry beans

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Leguminous Food Crops

Source: J.R. Myers CSS 330 lecture notes, 2003, OSU

Fabaceae (Leguminosae)

The bean family (Fabaceae) comprises about 550 genera and 12,000 species, including herbs, shrubs, and trees of world-wide distribution. Members of this family are dicots (dicotyledons), which means that the seeds typically contain two storage leaves (cotyledons). The cotyledons of the most important food crops in this family are rich in oil and high-quality protein.

The Fabaceae can be divided into three subfamilies:

  • Mimosoideae (Mimosa)
  • Caesalpinoideae (Redbud, Honey Locust)
  • Papilionoideae (beans, peas, and most other common legumes)

How do Legumes differ from other families?

  • Nitrogen fixers - they form symbiotic relationships with soil bacteria that fix atmospheric nitrogen into a form that can be used by plants.
  • They probably evolved in weathered, low fertility tropical soils - they are often used in crop rotations to help enrich the soil with nitrogen. Many legume crops are warm-season annuals that can be grown with modest amounts of rainfall.
  • They may have simple leaves, but many species have leaves that are palmately or pinnately compound, as shown in the picture on the right.
  • Distinctive flower shape - the bottom petals are joined together to form a keel that resembles the keel of a boat. Typically there are two side petals called wings and one petal on top called the standard.
  • The fruit is a pod or legume, that has one row of seeds
Photos courtesy J.R. Myers

Why Eat Legume Seed?

  • They are high in protein (20 – 35%)
  • Complex carbohydrates
  • Source of iron, vitamin B, folic acid, soluble fiber
  • Proteins complementary to cereal grains
    • High in lysine
    • Low in sulfur containing amino acids (cysteine, methionine)
    • Cereal grains are high in methionine

Antinutritional factors

  • Trypsin inhibitors (heat inactivated)
  • Alpha-amylase inhibitors (heat inactivated)
  • Hemagglutinins (heat inactivated)
  • Tannins (genetic differences exist among cultivars)
  • Phytate (chelates minerals and vitamins)
  • Indigestible starch and alpha-oligosaccharides (source of flatulence)

Eaten in a 3:1 cereal:legume ratio

  • Common bean and maize (New World)
  • Cowpea and sorghum or millet (Africa)
  • Pea, lentil, or chickpea and cereal (Western Asia & Europe)
  • Soybean or Vigna and rice (Eastern and Southern Asia)

Types of Grain Legumes

Oil seeds: soybean, groundnut
Grain legumes: bean, cowpea, etc.
Pulses: pea, lentil, chickpea

Note: The nomenclature of grain legumes may vary from scientific community to industry and business and from one country to another, and trade classes may be different in one continent compared with another. Here is the explanation of the terms above from the European Association:

"Grain legumes are cultivated primarily for their grains which are harvested at maturity and marketed as dry products rich in proteins. ...The major grain legumes grown in the Europe are: peas, soyabeans, faba beans, lupins, chickpeas, lentils and Phaseolus beans.

The mature grains of grain legumes are marketed as dry products usually called pulses in the trade and industry sectors. They are exploited primarily for their rich protein content. This term pulses excludes the ‘leguminous oilseeds’, such as soyabeans, which are used primarily for their high oil content which is extracted by industrial processes."

Uses of Leguminous Food Crops

  • Dry seed: moist vs. dry cooking
  • Vegetable: immature pods, seeds, leaves
  • Fermented: tempeh, tofu, miso

World Production of Leguminous Food Crops

Average World Production of Grain Legume Crops and Pulses, 2000-2002

ha x 1000
Mt x 1000
Groundnuts in Shell
Beans, Dry
Peas, Dry
Broad Beans, Dry
Cow Peas, Dry
Pigeon Peas
Bambara Beans


Changes under domestication

  • Increase in seed size
  • Loss of seed dormancy
  • Loss of explosive pod dehiscence
  • Vine to bush
  • Loss of some antinutritional factors in some species (pea, lentil)


Recent domestication – factors determining whether the crop is used as a grain legume or a vegetable
Type Pod Fiber Wall Thickness Seed/pod at maturity Seed Type (pea)
Dry bean/pea Yes Thin Mature Round
Shell bean/pea Yes Thin Nearly mature Wrinkled or round
Romano or snow No Thin Immature Wrinkled or round
Snap pea or bean No Thick Immature to nearly mature Wrinkled or round

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Soybean Origin & Taxonomy

Photo from USDA-ARS


Origin and domestication

Soybean is thought to have originated in China about 4,000-5,000 years ago, most likely in the north and central regions. The first known records of soybean were made around 2,800 BC. The crop was considered to be one of the five ‘sacred grains’ of Chinese civilization.

The taxonomy of the genus Glycine is both complicated and controversial. It is currently divided into three subgenera:

  • Glycine (2n=40, 80)
  • Bracteata (2n=22, 44?)
  • Soja (2n=40)

The economic importance of the genus Glycine lies predominantly within the subgenus Soja. Glycine max, the soybean, is a summer annual herb that has never been found in the wild. It is the world's most important oil crop. It is self-pollinating with 2n=40 chromosomes.

Plants of Glycine wightii subgenus Bracteata are climbing vinelike perennials which have shown promise as a pasture legume in the tropics and sub-tropics.

Plants of Glycine ussuriensis of the subgenus Soja are annual twiny vines with small narrow trifoliate leaves, purple flowers, and small, hard, almost round seed of a black to dark brown color. The species grows wild in Korea, Taiwan, Japan, China and the Soviet Union.

Glycine ussuriensis is commonly called wild soybeans in English. It can be crossed with cultivated soybean and has been a useful donor for ‘novel genes’.

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Soybean Growth Requirements & Adaptive Traits

Unique features of Soybean

  • Dicot with C3 photosynthesis
  • Nitrogen fixation in root nodules - symbiosis with bacteria
  • Photoperiod sensitive
  • Seeds high in protein and oil
  • Stout taproot
  • Plants up to 100 cm tall
  • Erect bush and viney types, heavily branched
  • Trifoliolate leaves - 3 leaflets
  • Leaves normally pubescent (hairy)
    • Provides resistance to thrips and leaf hoppers
  • From 30 to 100 pods per plant
  • 2-3 beans per pod; round-oval shape; colors vary
  • Sensitive to water stress
    • May lead to abortion of pods or seeds
  • Soil temperature of 65 °F preferred for germination
  • Warmer temperatures during grain filling increase yields
Photo from USDA-ARS

Photoperiod Response

Control of time to flowering and maturity are important for optimal yields. Adaptation to harsher environments depends on length and timing of life cycles – allowing for escape of adverse conditions – more than ability to tolerate such environments.

In soybean, photoperiod strongly influences time of flowering and senescence. Flowering may be induced by short days as early as the 2-leaf stage.

Twelve maturity zones have been defined for soybean in North America. Varieties are limited to production zones that are 100 to 150 miles wide (from North to South). If a variety is planted too far north it will be too late to mature. If it is planted too far south, early maturity results in less than optimum yields.

Initial soybean introductions into the Northern US from China were reasonably well adapted due to similarity in latitudes. Few of the many introductions from China, Korea, and Japan have contributed to the modern gene pool, however, as northerly types flowered too quickly for the southern US. Varietal differences in daylength sensitivity were recognized as crucial to adaptation, leading to subdivision of soybeans into 12 maturity groups based on photoperiod response.

Nitrogen fixation

Legumes are valuable components of farming systems due their ability to form symbiotic relationships with Rhizobia (bacteria) in the soil. A legume provides the bacteria with energy-rich carbohydrates and some other compounds. Unlike any plant, Rhizobia (and some other microorganisms) can fix inert N2 gas from the atmosphere and supply it to the plant as NH4+ which can be utilized by the plant.

In order for biological nitrogen fixation to occur, Rhizobia must form effective root nodules on the legume host. Some Rhizobium species are very selective and will only form nodules on a particular host species. Others cross-inoculate many species. A major achievement in soybean research at the International Institute of Tropical Agriculture (IITA) in Nigeria was development of promiscuous soybean cultivars that could form a symbiotic relationship with indigenous strains of Rhizobia. Prior to this breakthrough, it was necessary to inoculate soybean cultivars with compatible Rhizobia - a practice that was not readily available to local farmers. Another objective of soybean improvement work at IITA is to breed cultivars that have a high potential for biological nitrogen fixation. These cultivars may be particularly valuable in rotation with staple food crops such as maize that have high requirements for nitrogen.

Drawing courtesy of IITA, Nigeria

Legumes can obtain up to 40% of their N requirements from N fixation. It is often counterproductive to apply N fertilizer to a crop such as soybeans, because increased N fertilizer will suppress nodulation and N fixation.

During soybean production two sources of N are used:

  • Soil nitrate (fertilizer), used early in season
  • After flowering begins, ureide from fixed N
  • Total seasonal N needs: average 275 lbs N/a for 50 bu/a yield

Types of soybean

1. Northern production types

  • Indeterminate
  • New stem and leaf growth can occur for several weeks after initiation of flowering
  • Temperate adaptation

2. Southern production types

  • Determinate
  • Stem and leaf growth ceases after flowering
  • Main stem terminates in cluster of pods
  • Warmer climate adaptation

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Soybean Production Statistics

Soybean is the most widely grown legume in the world.

The USA is by far the leading producer of soybeans, accounting for about 44% of global production. Yields tend to be the highest in several European countries, with Switzerland taking the lead with average yields of 3,734 kg/ha (data not shown in table).

Major soybean producing countries (averages 2000-2002)
Yield (kg/ha)
Production (Mt x 1000)


U.S. Soybean Production

Soybeans were first brought to Europe in the early 1700’s, and to America as early as 1765. It had only limited use as a forage crop until the 1920's.

From 1924-1926 the USDA-ARS carried out extensive soybean explorations, introducing 1,500 accession to the U.S. from NE China. This project lay the groundwork for commercialization and genetic improvement of the crop in the US.

In 1929, the first commercial plantings were made in the US for soy sauce. Oil extraction facilities were built in the 1930’s in the Midwest. Production expanded during WWII, as the crop served as a replacement for imported fats and oils.

The areas of greatest soybean production of both China and the U.S. are located within the 35 to 45 degree north latitudes. These areas have warm, temperate climates with moderate amounts of rainfall. In the US, soybean production is concentrated in the midwest. Yields are typically about 40 bu/acre. Although these yields are somewhat less than the major cereal crops, the acreage planted to soybeans is not much less than acreage for corn or wheat. The trends are for increased acreages of soybeans in the US. A popular system in the southern US is to grow a double crop of wheat followed by soybeans. The soybeans are often seeded directly into the wheat stubble.

Major U.S. soybean markets

  • $12.2 billion crop value
  • $6.6 billion exported in soybean, products


  • EU $1.14 billion
  • China $1.00 billion
  • Japan $0.76 billion
  • Mexico $0.68 billion


  • Phillipines $166 million
  • Canada $164 million


  • Mexico $39 million
  • Korea $34 million

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Soybean Quality & Utilization

Soybean Products

Soybean derived products
Photo from USDA-ARS

Since ancient times in Asia, soybeans have been processed and consumed in many ways. Soybeans must be cooked before they can be eaten in order to inactive trypsin inhibitors in the grain that interfere with normal protein digestion in humans.

Composition of soybean

  • 13-25% oil
  • 30-50% protein
  • 15-25% carbohydrate
    • ~15% soluble carbohydrates - sucrose, stachyose, raffinose, other
    • ~15% insoluble carbohydrate - dietary fiber
  • ~14% moisture, ash, other
  • 0-5% lecithin (natural emulsifier, lubricant)
    • Used in pharmaceuticals as protective coatings
    • also in candy (chocolate)

Nutritional aspects

  • Good protein quality
  • High in lysine and essential amino acids
  • Oil is rich in polyunsaturated fatty acids
  • no cholesterol
  • Good source of Ca, Fe, Zn, Mg, B vitamins, folate
  • Contain isoflavones, which are phytoestrogens - may help to lower cholesterol and reduce blood pressure, thereby lowering risks of cardiovascular diseases. May also help to prevent certain types of cancers.

Primary uses today in US

  • Soybean accounts for 80% of edible fats, oils
  • Protein-rich feed for poultry, pork, beef, fish, lamb
  • Margarine, shortening, mayonnaise, salad oil and dressings
  • Printing ink, dust suppressant

Food uses - Asia

Large immature green seeds used as vegetable

Edamame (Japan); Mao Dou (China)

  • As protein supplement to rice and wheat
  • Natto and Tempe
    • Snack foods
    • Natto - fermented in Bacillus natto
    • Tempe fermented in Rhizopus oligosporus
    • Small seeded varieties
  • Sprouts
  • Soy flour
  • Tofu (precipitated protein curd)
  • Soy sauce - soybeans are fermented in brine (most American brands are made synthetically)
  • milk, curd, paste
    • To prepare soy milk, beans are soaked in water and puréed. This product is an important nondairy alternative for individuals who are lactose intolerant and cannot digest cows' milk or for those who are allergic to milk proteins
  • Textured vegetable protein
    • Manufacture of glycerin
    • Protein rich feed for increased animal production
    • Meat extender in Europe

Soybean – Processing

  • Cleaned, cracked, dehulled, and rolled into flakes
  • Ruptures oil cells for efficient extraction
  • After removal of oil, flakes are processed into
    • Edible protein products
    • Protein meal for animal feed
    • Soy flour for dough conditioners in baking

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Arachis hypogaea (L.) has a number of common names including groundnut and peanut. Its center of origin is South America (Bolivia and neighboring regions). It is now widely distributed throughout the warm temperate and tropical areas of the world. Peanut is a self-pollinating, indeterminate, annual, herbaceous legume.

The fruit is a pod with one to five seeds that develop underground within a needlelike structure called a 'peg'. Eight to 14 days after pollination aerial pegs will grow 2 to 3 inches into the soil and then turn to a horizontal orientation to mature into a peanut pod.

Photo by David Nance, USDA  

Leading producers of groundnuts in 2002

Mt x 1,000

Percent of Total World Production
United States of America

China is by far the leading producer of groundnuts in the world. Average yields in that country were 2,897 kg/ha in 2002.

Most of the crop is produced where average rainfall is 600 to 1,200 mm and mean daily temperatures are more than 20 °C. Although the ideal growing season is relatively long (4-5 months), warm and moist, the harvest season must be dry to permit the pods to be pulled from the ground. The soils should be light and well-drained to facilitate penetration by the pegs and removal of pods at harvest.

The seed contains:

  • 25 to 32% protein (average of 25% digestible protein)
  • 42 to 52% oil
  • good source of vitamins E, K, and B vitamins

In most of the world, oil is the primary end-use of groundnut. In the United States, dry roasted peanuts and peanut butter are also important end-uses. Boiled peanuts are popular in Africa and can be purchased along the roadside as a snackfood. West African groundnut stew is also a popular dish.

Animal feed and fodder are important secondary uses of groundnut.

U.S. Peanut market types


  • Dominant type grown since introduction of high yielding varieties in the 1970’s
  • Attractive uniform kernel size, slightly smaller (700 kernels/lb) than Virginia type
  • Grown in warmer, humid areas: Georgia, Alabama, Florida, Texas, Oklahoma
  • 54% of runner types are used for peanut butter


  • Largest seeds (500 kernels/lb)
  • Account for most of the roasted, processed in-the-shell market
  • Larger kernels sold as snack peanut
  • Grown in SE Virginia, NE N. Carolina


  • Smaller kernels (1000-1400/lb) covered with reddish-brown skin
  • Rarely more than 2 seeds/pod
  • Used predominantly in peanut candies, snack nuts, and peanut butter
  • Higher oil content than other peanuts
  • Bunch type, erect growth
  • Grown in more arid climate: Oklahoma and Texas


  • Three or more small kernels to a pod covered with bright-red skin
  • Sweet peanuts, usually roasted and sold in-the-shell
  • Also for fresh use as boiled peanut
  • Relatively less important, limited acreage in New Mexico

U.S. production of peanuts is worth over $4 billion per year.


Diseases are major constraint to world production of groundnuts. A large number of diseases caused by fungi, bacteria, viruses, mycoplasma, nematodes, and parasitic flowering plants have been reported, and with some exceptions, they are widely distributed. All parts of the groundnut plant are susceptible to diseases.

Aphids are carriers of the groundnut rosette virus, which is a devastating disease in sub-Saharan Africa. An entire crop may be lost during an epidemic outbreak. Sources of resistance to the virus are available.

Mycotoxin contamination

Pre harvest infection of peanut with toxigenic fungi, especially Aspergillus spp., poor management practices during and after harvest, and adverse storage conditions all can result in contamination of peanut and peanut products by mycotoxins, especially aflatoxins.

Aflatoxins are a serious health hazard for humans and livestock and have been associated with liver diseases and other public health concerns. In drought-prone regions of the world, the infection is encouraged by terminal drought stress. The presence of aflatoxins on peanuts has limited the extent to which the crop can be traded on international markets. Sources of resistance to the causal organism, Aspergillus flavus, have been identified and are being used in groundnut breeding programs.

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Dry Beans

Source: J.R. Myers CSS 330 lecture notes, 2003, OSU

Phaseolus vulgaris L. - Common Beans

  • Warm Season crops
  • Diploid (2n = 22)
  • Self-pollinated
  • Maintained as pure lines
Dry Beans vs. Snap Beans
Dry beans are cultivated for mature seed Snap beans are selected for succulent, fiber free pods eaten at an immature stage
Photos courtesy J.R. Myers, OSU

Centers of Domestication

1. Andean

  • Large Seeded
  • Kidneys, Cranberries, Nunas, and many Snap Beans

2. Mesoamerican

  • Small and Medium Seeded
  • Navy, Black, and Small Central American Reds
    Pinto, Pink, Great Northern, Red Mexican, and some Snap Beans

Common Bean Growth Habits

Type 1 (determinate bush)
Type 2 (upright indeterminate short vine)
Type 3 (sprawling indeterminate)
Type 4 (climbing indeterminate)

Green Bean Quality

  • Shape
  • fiber, color
  • slow seed development
  • inter-locular cavitation
  • pigments
  • mostly quantitative inheritance

Green Bean Diseases

White & Gray mold

White Mold (Sclerotinia sclerotiorum)

  • Overwintering sclerotia produce apothecia
  • Apothecia release ascospores
  • Senescent bean flowers provide foothold for the pathogen
  • Mycelia excrete oxalic acid, pectinases, etc.



Photo courtesy J.R. Myers, OSU

Root Rot complex
(Pythium, Rhizoctonia, Fusarium)




Photo courtesy J.R. Myers, OSU

Bean/Cowpea CRSP - Bean Breeding in Africa

Collaborative project:

  • OSU
  • UC Davis
  • National breeding programs of Tanzania and Malawi

Bean Production in Africa

  • Primarily in the highland areas or places with more moderate climate and higher rainfall
  • Mostly a subsistence crop
  • Some cash cropping and export
  • Fledgling market system
  • Commonly grown in mixed cropping systems

Bean with maize
Bean in an alley cropping system
Bean with banana
Photos courtesy J.R. Myers

Africa has:

  • Greater genetic variability (for some traits)
  • Greater variation in environments
  • Large seeded Andean bush types predominate
  • Climbers are important in the highlands of Malawi


  • Heat and Drought
  • Bruchids
  • Bean Stem Maggot
  • BCMV - bean common mosaic virus
  • CBB & HB - common bacterial blight and halo blight
  • ALS - angular leaf spot
  • Rust
  • Nematodes
  • Lack of Infrastructure!

Several varieties have been released in Malawi and Tanzani as the result of this project.

Breeding for Bruchid Resistance
  • RAZ backcross lines (arcelin-1)
  • Rojo, SUA-90, EP3-2, C11, C12
  • In on-farm trials with release planned 2000/2001


Photo courtesy J.R. Myers, OSU

Susceptible vs Resistant Variety

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Take the quiz on this Unit on the Blackboard.

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Levetin, E. and K. McMahon. 2005. Legumes. Chapter 13 In Plants and Society, 4th edition. McGraw-Hill, New York, NY. Additional on-line notes and references:


American Soybean Association. 2006.

Ashlock, Lanny. 2006. Arkansas Soybean Handbook. Publication MP 197, Cooperative Extension Service, University of Arkansas.

ISU Cooperative Extension Service. 1994. How A Soybean Plant Develops. Special Report #53.

National Soybean Research Laboratory. University of Illinois.

North Dakota State University Extension Service. 1999. Soybean Growth and Management Quick Guide. http://www.ext.nodak.edu/extpubs/plantsci/rowcrops/a1174/a1174w.htm

Purdue Links for Glycine max (L.) Merr. 2003.


ICRISAT. 2005. Groundnut.

Phillips, S.L. 1997. The incredible peanut. Ethnobotanical Leaflets, Southern Illinois University Carbondale

Purdue Links for Arachis hypogaea L. 2001.

Putnam, D.H., E.S. Oplinger, T.M. Teynor, E.A. Oelke, K.A. Kelling, and J.D. Doll. 2000. Peanut. Alternative Field Crops Manual. University of Wisconsin Cooperative Exension and the University of Minnesota Extension Service.

Virginia-Carolina Peanuts. 2005. http://www.aboutpeanuts.com

Common Bean

CIAT. 2003. Bean Improvement. http://www.ciat.cgiar.org/beans/

Purdue Links for Phaseolus vulgaris L. 2001.

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