Introduction

The soybean [Glycine max (L.) Merr.], together with wheat [Triticum aestivum L.], maize [Zea mays L.], rice [Oryza sativa L.], barley [Hordeum vulgare L.], sugarcane [Saccharum officinarum L.], sorghum [sorghum bicolor (L.) Moench], potato [Solanum tuberosum L.], oats [Avena sativa L.], cassava [Manihot esculenta Crantz], sweet potato [Ipomoea batatas (L.) Lam.], and sugar beet [Beta vulgaris L.], are the principal food plants for humans (Harlan, 1992; Kasmakoglu, 2004).

Of the food plants, the soybean is unique in that the traditional foods in Asia made from the soybean (e.g., tofu, miso, and soy sauce) bear no semblance to or association with the crop growing in the field. The word soy comes from the Japanese word shoyu and first appeared in a Japanese dictionary published in 1597 (Shurtleff & Aoyagi, 1983). The popularity of tofu (bean curd) in China took place during the latter half of the Song Dynasty (960–1279 ce) (Shinoda, 1971). Miso is fermented soybean paste that originated in China around the first century bce. Today, Westerners refer to it by its Japanese name (Shurtleff & Aoyagi, 1983). The Chinese word for soy sauce is jiang-you. Supposedly, it originated prior to the Zhou Dynasty (before 211 bce) (Shurtleff & Aoyagi, 1983).

In the West, the two main products of the soybean are seed oil and the protein-containing meal. Soybean seeds contain 18–23% oil and 38–44% protein on a moisture-free basis. The oil is converted to margarine, mayonnaise, shortening, salad oils, and salad dressings. The meal is used primarily as a source of high-protein feeds for the production of pork, poultry, eggs, fish, beef, and milk. The soybean protein also is used in the form of protein concentrates and isolates, and texturized protein for human consumption (Hymowitz & Newell, 1981). Today, soy is taken for granted without appreciable forethought as to by whom, when, where, and how the soybean was domesticated in China for human use; by whom and when the soybean was disseminated throughout the world; and where the wild relatives of the soybean are and can they be exploited for the development of improved cultivars (Hymowitz, 2004). Unfortunately, the popular literature concerned with the historical development of the soybean is fraught with errors and misconceptions that keep recycling from one publication or Web site to another without proper documentation (Hymowitz & Shurtleff, 2005).

In the past, studies on the domestication of the soybean were extremely difficult for two main reasons: i) the soybean is autochthonous to the Orient, where Western scientists were at a linguistic disadvantage with respect to historical records. However, in the past 40 years, classical Chinese works were translated into English; establishment of international soybean symposia (e.g., the World Soybean Congress) enables Chinese and Western academicians interested in soybean history to meet and discuss common issues on a regular basis; and lastly, molecular studies on soybean germplasm resources are beginning to answer questions that were not asked previously; and ii) many libraries were loathe to permit research scholars to handle fragile pages of archived manuscripts, books, and newspapers. However, today commercial companies scan and digitize many key documents and place them on the Internet, and these documents are available on commercial and public Web sites, especially at large research institutions.

This chapter attempts to combine information from many disciplines to establish a solid foundation for understanding the history of the soybean.

The Genus Glycine and its Immediate Allies

The genus Glycine Willd. is a member of the family Fabaceae/Leguminosae, subfamily Papilionoideae, and tribe Phaseoleae. The Phaseoleae is the most economically important tribe. It contains members that have considerable importance as sources of food and feed, for example, Glycine max—soybean; Cajanus cajan (L.) Millsp.—pigeon pea; Lablab purpureus (L.) Sweet—hyacinth bean; Phaseolus spp.—common bean, lima bean, tepary bean; Psophocarpus tetragonolobus (L.) DC.—winged bean; and Vigna spp.—azuki bean, cow pea, and Bambarra groundnut (Hymowitz & Singh, 1987).

Within the tribe Phaseoleae, Lackey (1977a) recognized 16 genera of the subtribe Glycininae, which he subdivided into two groups, Glycine and Shutaria, based upon morphological alliances. The Glycine group is distributed in the Old World with the exception of Teramnus, which has a pantropical distribution. The Shuteria group represents all of the other Glycininae. Polhill (1994) transferred Calopogonium and Pachyrhizus from the subtribe Diocleinae sensu Lackey (1977a) to Glycininae and reorganized 18 genera within Glycininae (see Table 1.1.).

Lee and Hymowitz (2001) studied the phylogenetic relationships among 13 genera of the subtribe Glycininae inferred from chloroplast DNA rps16 intron sequence variation. Phylogenies estimated using parsimony and neighbor-joining methods revealed that: (a) the genera Teramnus and Amphicarpea are closely related to Glycine and (b) the genus Pueraria regarded as closely related to the genus Glycine is not monophyletic and should be divided into at least four genera, an idea previously supported by Lackey (1977a).

Pueraria montana var. lobata (Willd.) Maesen and A.M. Almeida (ILDIS, 2006) commonly is known as kudzu. These days it thrives as a weed throughout the southeastern part of the United States. Kudzu also acts as an alternate host for the economically important pathogen Phakopsora pachyrhizi Syd. The fungal pathogen known as soybean rust over winters on kudzu in frost-free environments along the U.S. Gulf Coast. It was first identified in the continental United States in 2004. Soybeans are very susceptible to soybean rust and, if infected and left untreated, the plants quickly defoliate and die. How much damage will occur to the soybean crop in the future by the pathogen is uncertain.

The Taxonomic History of the Genus Glycine

Glycine has a confused taxonomic history, which dates back to the time of its first inception. The name Glycine was originally introduced by Linnaeus in the first edition of his Genera Plantarum (Linnaeus, 1737), and is based on Apios of Boerhaave (Linnaeus, 1754). Glycine is derived from the Greek glykys (sweet) and probably refers to the sweetness of the edible tubers produced by G. apios L. (Henderson, 1881), now Apios...