The Soybean Plant: Botany, Nomenclature, Taxonomy, Domestication, and Dissemination - Page 1

by William Shurtleff and Akiko Aoyagi


A Chapter from the Unpublished Manuscript, History of Soybeans and
Soyfoods, 1100 B.C. to the 1980s

©Copyright 2004 Soyfoods Center, Lafayette, Californi

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In the following discussion, unless otherwise specified, the term "soybean" will be used to refer to the domesticated soybean, Glycine max (L.) Merrill, which in 1980 was one of the world's major crops, covering more than 53 million hectares of farmland worldwide. The term "wild soybean" will be used to refer to Glycine soja Siebold & Zuccarini, the earliest wild ancestor of today's cultivated soybean. These two plants are easily crossed and, technically, they are of the same species. However since their uses and characteristics are very different, they have been given two species names.


The earliest wild soybeans bore little resemblance to their present cultivated descendants. Originating in East Asia prior to 1000 BC, the wild soybean was an annual twining vine with small and narrow trifoli-oblate (explain??) leaves, very small purple flowers, and small, hard, roundish black to dark brown seeds. Today the plant grows wild north from Taiwan into the Yangtze river valley, northern and northeastern China, Korea, Japan, and the USSR (Hymowitz 1970). Each of the tiny wild soybean seeds probably weighed only about one-ninth as much as today's US cultivated soybean. Yields of the seed were very low (only about one-fifth of present US yields) and the seeds tended to shatter (drop from the pods) quite easily when they reached maturity. Interestingly, the seeds of this wild soybean were very low in oil compared to today's US cultivated soybeans (9.8% vs. 21%) and quite high in protein (46% vs. 40% today??) and in the key sulfur-containing amino acids methionine-cystine (??% vs ??%). (Hymowitz 197??).

The geneticist Harlan (19??) has commented that "Fully domesticated plants are artifacts produced by man as much as an arrowhead, a clay pot, or a stone ax." Today's cultivated soybeans bear witness to careful selection during more than 30 centuries. In domesticating the wild soybean, primitive farmer-breeders selectively kept seeds each year from their largest seeded and highest yielding plants, then planted them the next spring in hopes of increasing their yields, their total weight of food harvested per unit area of land. Agronomists and geneticists now know that if they work to increase soybean yield, they tend to produce seeds with increased oil content and decreased protein; an increase in oil content by 2 percentage points is almost inevitably accompanied by a decrease in protein content by 1 percentage point. This helps to explain why today's higher-yielding soybeans contain more oil and less protein than their wild ancestors. In addition to increasing the oil and decreasing the protein content of the seeds, the process of domesticating the wild soybean and transforming it into today's cultivated soybean involved creating a plant with more erect growth habit, less shattering of the seeds from the pods, and less twining (all of which facilitate harvesting, especially by machine), less sensitivity to photoperiod (day length, as governed by latitude; this facilitates north-south dissemination of the plant), larger plant size (large plants bear more seeds), larger seed size (giving higher yields, easier shelling, and a higher ratio of cotyledons to hulls), and a higher proportion of yellow seeds (which give a lighter colored oil and meal) (Hymowitz 1976 Ref??).

Today's soybean plans are 24-36 inches in height, bearing typically 100-150 pods??. Prior to the 20th century, soybeans bearing non-yellow seeds were very common worldwide: black, green, brown, yellowish green, or mottled; today's seeds are largely straw yellow. The seeds grow in pods (usually 2-3 to a pod) attached to the plant's stem. The plant has trifoliate leaves. The leaves, pods, and stems are typically covered with soft brown hairs. The roots bear nodules formed by Rhizobium japonicum , which extract nitrogen from the air and fix it in the soil, where it stimulates the growth of both the soybeans themselves and of other crops planted later in the same place. Soybeans typically mature and are ready to harvest 90-100 days after they are planted, however there are very early varieties that mature in only 75 days and very late varieties that take 200 days or more.

There is considerable variability in the size and chemical composition of the seeds of today's cultivated soybeans??. The seeds range in size from 8-50 grams per 100 seeds, or a sixfold range (vs. 1.8 to 3.2 gm per 100 seeds of the wild soybean). Protein ranges from 35.1 to 52.2% (on a moisture-free basis), methionine from 1.0 to 1.6%, oil from 11.4 to 23.4%, and linolenic acid (a fatty acid in the oil that is generally considered undesirable) from 4.3 to 15.0%. Hymowitz 1980; U of I SANA speech). Soybeans grown commercially in the US in 1970 contained 39 to 45% protein and 20 to 23% oil (Wilcox 1970 Ref??).

Four basic concepts characterizing soybeans which must be understood before we can discuss their history are photoperiod sensitivity (photoperiodism), maturity groups, vegetable type versus field type soybeans, and determinate/indeterminate growth habit. (1) Photoperiodism. Soybeans are unique among legumes in that they contain a built-in time clock; their flowering and ripening is controlled not like most plants by the air temperature, but by the length of the day and night, the photoperiod. Since daylength changes with latitude, most soybean varieties will only produce a good crop in a band no wider than 150 miles from north to south. North of this band, the variety will flower and mature later than is desirable; south of it, earlier. (2) Maturity Groups. In North America, starting in the late 1920s??, soybeans came to be classified into 12 maturity groups (MG) based on photoperiod sensitivity (daylength response). Soybeans grown in Canada and the northern parts of the US are classified as MG 00 and 0, respectively. Those grown in the central US belong to MG II (or I??) through IV, whereas those adapted to the subtropical and tropical zones are classified as MG IX and X (Fig. 2.XX). Varieties suited to the northern maturity groups mature quickly, in about 80-90 days after planting, whereas those in southern warm climates take longer, 100-150 days. (3) Vegetable type soybeans (also occasionally called edible- or garden type soybeans) are larger seeded, somewhat better tasting, and easier to cook and shell than field type soybeans. They were introduced to the US from north Japan and Korea in the 1930s. Roughly 99% of the soybeans in the US in 1980 were the field type. There is no basic genetic or chemical/nutritional difference between the two types. (4) Determinate type soybeans complete their vegetative growth prior to flowering and the main stem ends in a rather large terminal raceme (group of flowers along the stem). Indeterminate growth-type varieties continue to increase in height for several weeks after beginning to flower. Presently, all commercial soybeans grown in northern latitudes (MG 00 through IV) have an indeterminate growth habit, while those in the more southern groups V to VIII have a determinate habit.


The earliest known name for the soybean was shu , a term used in north China as early as the 11th century BC. By the ??th century the term dadou (ta-tou; literally "great bean") came to be the standard Mandarin term for the soybean, as it is today. According to the P'ei-wen yun-fu ^ (Ref??), a famous dictionary of literary phrases, the term dadou first appeared in the Huai-nan tzu written in about 130 BC (Ref??). This book was written by scholars at the court of Lord Liu An of Huai-nan, the man traditionally named as the discoverer of tofu. The term dadou was widely used during the Han dynasty; both Ts'ui shih and Fansheng in their books on farming techniques mention cultivation of dadou and its use in famine relief. In the new pinyin system it is romanticized as dadou . In Japan today these same characters (logographs) are used to write the word soybean, but they are pronounced "daizu," a term which first appeared in the classic Kojiki (Record of Ancient Matters) in AD 712 (Philippi 1968).

Since ancient times in China the soybean was considered the most important cultivated legume and one of the five sacred grains (called wu-ku in Chinese and go-koku in Japanese); namely millet ( shu ), millet ( chi ; both these millets are subspecies of Panicum miliaceum ), rice ( tao ), wheat and barley ( mai ), and soybeans ( shu ). The term wu-ku , mentioned in mythological writings (Chang 1982 Ref??), first appeared in China in about X00 BC in the (what book??). Living close to the earth, the people of China clearly understood that their lives and civilization depended on these basic crops. Their sense of the sacredness of these grains evolved, no doubt, from both a deep gratitude and an awe at the mystery of their interrelationship with other living things.

In China the word "bean" invariably refers to the soybean. In 1901 Hosie wrote that within the general term for soybean ( dadou ), the Chinese distinguish three basic commercial varieties of soybeans by their color: yellow ( huang tou ), green (ch'ing tou), and black ( hei- or wu tou ). Each color was considered a variety, and each variety had sub-species. The yellow had three, known respectively as Yellow Eyebrow ( pai-mei , from the white seed scar on the hilum), Yellow Golden or Golden Round ( chin-huang or chin-yuan ), Black Belly ( hei chi , from the dark brown seed scar on the saddle). All three were highly prized for the oil they contained; the first and second were especially famous for making tofu and soy sprouts. There were also two named subspecies of green soybeans and three of black. Two of the black were widely used to make the fermented soyfood we call soy nuggets (see Chapter 18).

In addition to the names of these basic varieties, East Asian soybean growers have long assigned poetic names to soybean types which describe important qualities such as seed size (Large Jewel), seed shape (Round Pearl), hilum/seed scar character (Flowery Eyebrow, Blackeye), maturity (Early Gold), seed coat color (Yellow Jewel, Black Saddle), utilization (White Sprout, Miso, Shoyu), or superiority (Brings Treasure, Great Happiness). Other names were apparently chosen solely for their beauty: Heaven's Bird, White Spirit of the Wind, Flower Garden, Clasped Hands (Morse 1951). Two of the most popular soybean varieties in Japan today are Child of the White Crane ( tsuru-no-ko ) and Waving Sleeves ( sodefuri ??).

There are a number of theories concerning the origin and etymology of the English and American terms soya bean and soybean. The most widely held theory (outlined in the Oxford English Dictionary , the Oxford Dictionary of English Etymology , and Webster's Dictionary ) is that in the late 1600s the terms were borrowed from the Dutch soja , which, in turn, was probably derived from the Japanese shoyu , meaning "soy sauce," or, less likely, from soy , a supposed Japanese colloquial form of the term shoyu . It is generally thought that the Japanese term shoyu derives from the Japanese reading of the Chinese characters jiangyou , also meaning soy sauce, however several etymologists believe that the term shoyu was formed in Japanese first and that the Chinese formed their own compound (in characters) on the Japanese model. There are two points of interest concerning this theory. First, in all European languages, the terms "soy, soya, soja" or their equivalents referred initially to soy sauce and not to soy beans , indicating that Europeans were aware of the former long before they were aware of the latter. Second, indicating a problem with the theory, the earliest known mentions of cognates of the word "soy" appear in English rather than in Dutch publications, as described below. Are there earlier Dutch references not known in English?

A second theory, first mentioned by Piper and Morse (1923) and repeated in the Encyclopedia Britannica , states that in the Chinese dictionary Kouang-ia , dating from the beginning of the Christian era, the soybean was called both ta-tou (ta-teou) and sou ; the latter Chinese term was very probably the source of the terms soi (Malay), soy, soya, and soja . A third theory is that the English "soy" derives from the Chinese terms shi-yu or shi-yao ; shi is "soy nuggets or salted black beans" (see Chapter 18) and yu is the liquid extracted from them, perhaps China's first "soy sauce." The Japanese term shoyu could not have been derived from these terms since the characters are different. A fourth and less widely known theory set forth by Oshima (1905) is that in Japan large, protein-rich, late-maturing types of soybeans especially adapted for making shoyu are called "shoyu beans;" the Western name "soy bean" very probably owes its origin to this fact.

Let us look more carefully at the first theory given above. The first Europeans to reach Japan were the Portuguese; a Portuguese ship landed at an island off southern Kyushu in 1543. From 1849, under the leadership of St. Francis Xavier, they were doing active missionary work. In 1609, the Dutch first reached Japan, landing at an island off northern Kyushu, followed in 1613 by an English ship. Both Holland and England established trading missions with Japan, but neither of these Protestant nations was interested in missionary work. During the early 1600s the Japanese stamped out Christianity in Japan and expelled all Europeans, except for the Dutch, who, in 1641, were given a small artificial island, Deshima (or Dejima), in Nagasaki harbor, where they were kept almost like prisoners but allowed to establish a small trading post. For the next two centuries, the Dutch were the only Europeans allowed to visit Japan, and they were allowed but one trading ship a year. It was through this contact, and through the required annual visit of a Dutch mission to the Japanese capitol at Edo (Tokyo), that the Dutch came to learn about shoyu and the word soja entered their language. It would be very interesting to know the first reference to soja in Dutch.

This word entered the English language in the late 1600s (Murray 18??; Yule and Burnell 1903). In 1679 the Englishman John Locke made the earliest known mention of a term closely related to "soy" in his Journals (first published in 1830; King 1858. Why 1830??): "Mango and siao are two sorts of sauces brought from the East Indies." In 1696 the Englishman J. Ovington stated in his Voyage to Surat : "Souy is the choicest of all Sawces." In 1699 the Englishman?? Dampier, in his Voyages , first spelled the word as it is spelled in America today: "I have been told that soy is made partly with a fishy composition . . . " In 1705 the Englishman Dale first used the term "soia." In 1712 the German Englebert Kaempfer, writing in Latin in his Amoenitatum Exoticarum referred to Japanese shoyu as sooju . In Mrs. Glasse's Cookery (1747-96 Ref??) it is advised to "Dish them up with plain butter and soy." The 1771 translation of Osbeck's Voyage by J.R. Forster makes the first mention of the present British term "soya," stating that "The Japan soya is better and dearer than the Chinese." And the 1779 issue of the Encyclopedia Britannica states that "This legumen . . serves for the preparation . . of a pickle celebrated among them (the Japanese) under the name of sooju or soy." Many other mentions occur thereafter ( The Oxford English Dictionary , 1919). Note that every early mention refers to the sauce and not the bean or the plant. (The word "bean," incidentally traces its origins back to the ancient Latin term faba which became baun in Old Norse, bona in Old High German, and bean in Old English.) Thus the word "soybean" traces its ancient ancestry to the Japanese term for "soy sauce" and the Latin term for "bean."

Now, what did Europeans call the plant during this period? The first known reference to the soybean plant was by the German botanist Kaempfer who in 1712 called it "daidsu" (his rendering of the Japanese word for soybean, daizu ) or "mame" (the original Japanese term for "bean"). In 1747 the Dutchman Rumphius called it Cadelium (Kadelee), a derivative of its name kedelee in the Dutch East Indies (today's Indonesia), where he had observed it. In 1753 the Swedish botanist Linnaeus called it Dolichos soja ; this was also its first scientific name, and the first time the "soy" cognate had been used to describe the plant. In 1794 the German Moench suggested a new scientific name, Soja hispida (from the Latin hispidus , meaning "covered with stiff hairs). Thereafter the term "soja" appeared in most of the plant's many changing scientific names, except the present one, Glycine max .

It was in America that the plant first came to be widely referred to by popular names rather than by a scientific name. It is doubtful that there are many plants in America that have had more different names with different spellings than the soybean (Bowen 1767, Frankin 1770). It has been known variously as the soy-bean, the soja, the Japan pea, the soja bean, the stock pea, the soy bean, the soya bean, and the soybean. The first mention of the plant in America in Pennsylvania in 1804 referred to it as both "the Soy-bean" and "the Soja ( Dolichos soja , L.)." Who? Articles in 1829 and 1831 referred to the plant as "soy bean." In 1853 Ernst of Ohio was the first to refer to the plant as the "Japan pea," which remained the most popular term until the late 1870s and continued to be used as late as 1905. It was later also called the "Japanese pea," the "Japan fodder plant," and the "Japan bean," although the latter term was more widely used for the azuki bean. [In 1854 the soybean was first referred to as the "coffee berry" by Moore's Rural New Yorker, presumably because the seeds were roasted and ground for use as a coffee substitute; Ref?? Not T.E.W 1854. Probably not true]. In 1874 the American Agriculturalist first referred to the plant as the Soy Pea ( Glycine soja ), which it distinguished from the Japan pea. The former was said to be used to make a sauce called "Soy." The latter was accompanied by an attractive engraving, showing it to be a soybean. The term "Soy Pea" was used into the 1890s. In 1879 Cook, of Rutgers in New Jersey, was the first to call the plant "the soja bean," which remained the most popular term until the early 1890s, but was not used after 1898. In 1881 McBryde at the University of Tennessee was the first to use the modern term "the soybean" spelled as one word, but in 1890 he switched to calling the plant "the soja bean" as was then the fashion. In 1882 the Rural New Yorker published a short article by an anonymous New York writer who called the plant "the hairy soja bean" During the 1890s the term "soybean" was almost as popular as "soja bean." In 1894 in North Carolina, then America's leading soybean producing state, the agricultural experiment station bulletin (Ref??) referred to the plant as the "Japanese pea, Mongolian pea, or Soy pea" saying that it is "more commonly called `soja' and `soy' bean, but it is not a bean." In the early 1900s the plant and its seeds were known in North Carolina as the "stock pea (Ref??)."

In 1895 Brooks of the Massachusetts Hatch Agricultural Experiment Station was the fist American to use the British term "soya beans;" in two prior publications he had used "soybeans." The British term was used several more times in publications in the early 1900s (e.g. Carson 1909), then became dormant, only to resurface with vigor in the mid-1930s when "soya" became the US Department of Agriculture's preferred term for use with foods, especially "soya flour." It was also used from 1939 by the Soy Flour Association. Apparently the word "soya" was considered more euphonious and/or more international in sound than the compact and easy-to-pronounce "soy." Moreover, "soya" was occasionally considered more versatile in being able to embrace both the concept of "soybeans" and of "soyfoods," as in contemporary usages such as "Soya Bluebook" or "International Soya Protein Food Conference." Thus has the term "soya" survived.

The old two-word spelling "soy bean," first used in 1829 and 1831, was revived starting in 1898 by the USDA Bureau of Plant, who listed the "soy Bean" in their Inventory No. 1 of Foreign Plants and Seeds. This became the preferred USDA spelling being used by Abel in 1900, and more important from 1909-1922 by Piper and Morse, pioneers of the crop in America. The term "soy bean" remained the preferred spelling in America until about 1924, at which time the present one-word spelling "soybean" became most popular. As mentioned above the one-word spelling had first been used in 1881, and was fairly widely used during the 1890s. It was revived in 1920 by the National Soybean Growers Association, who spelled it as one word in their name, then given great impetus by the publication in 1923 of Piper and Morse's classic The Soybean . (Interestingly, Morse continued to write "soy bean" in USDA publications until the late 1920s.) From 1924 on, the majority of agricultural experiment stations used the term "soybean" and in 1935 the prestigious Chemical Abstracts switched from "soy bean" to "soybean." Yet the two-word spelling persisted into the early 1940s, prompting Pellett (1944), an editor?? of the Soybean Digest , to write an article titled "Say `Soybean,'" based on a list of soy-related terms originally proposed by Whitney Eastman of General Mills. The article urged that the word "soybean" be used in reference to the plant, the beans, the producer ("soybean grower"), the processing industry ("soybean processor") and to "soybean meal." All food related terms should drop the word "bean" and use only "soy," as in "soy oil, soy flour, or soy sprouts." The term "soya" (as in "soya flour") was listed as acceptable but not preferred. This article played a key role in establishing the modern soy-related terminology. The only important terminology changes in America since the 1940s have been the condensation of "soy milk" to "soymilk" and the creation in 1976?? of the general term "soyfoods" to replace such awkward terms as "soybean foods" or "soy protein foods," or the rarely used "soy foods."

Today in Europe soybeans are called "soya beans" in British, "le Soya" in French, "die Soja (pronounced SO-juh) or die Sojabohnen" in German, "soyabonen" in Dutch, "frijoles de soja (pronounced SO-ha) or soya" in Spanish, and "fagioli di soia" in Italian. Most of these terms have remained unchanged since the 1870s. Only the French term underwent numerous changes from "pois oleagineux" in 1855 to "Pois a^ Soja, Dolichos Soja, haricot soja, pois soja, and soja hispida" in 1862, to "Dolichos soja" in 1878, and finally to the present "le Soya" and the alternate "Haricot Haberlandt" in 1880. For more details on this evolution in French, see Chapter 32. A list of worldwide vernacular names of the soybean is given in Piper and Morse (1923, p. 35).

It is interesting to note that in English, beans are treated as a countable noun, whereas grains are treated as noncountable??; hence, we say "a bushel of soybeans" but not "a bushel of wheats, rices, and corns." Also, we use the terms "the soybean" and "soybeans" more or less interchangeably. In a number of Third World countries such as Indonesia or the Philippines, where this usage may seem illogical and cumbersome, soybeans are sometimes (often?? starting when??) treated as a noncountable noun, like rice or wheat. Thus they might say "a bushel of soybean" or "Soybean is widely cultivated in China."


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