ABSTRACT

Soybean (Glycine max L. Merr.) is a member of the legumes, the third largest family of flowering plants. The legumes are critical in global agriculture, providing the majority of plant protein, and more than a quarter of the world’s food and animal feed (Graham and Vance 2003). The legumes are highly diverse, with more than 20,000 species and 700 genera, three commonly recognized subfamilies, and origin around 60 million years ago (MYA) (Doyle and Luckow 2003; Cronk et al. 2006). The family is unusual in its ability to fix nitrogen, through association with Rhizobia bacteria. The legumes are also of interest for the diverse biochemistries enabled by their greater access to nitrogen, and for their structural genomic evolution. The legumes show large variation in chromosome numbers and genome sizes, driven partly by episodes of polyploidization in the family (reviewed in Shoemaker et al. 2006), and partly by different rates of amplification and elimination of repetitive DNA, as has been observed in other plant species (Kumar and Bennetzen 1999; Devos et al. 2002; Ma et al. 2004). On the other hand, comparative genetic mapping and recently expanding comparative genomic sequence analyses from multiple legume species have demonstrated extensive macro-and micro-colinearity of genes (Choi et al. 2004; Cannon et al. 2006; Schlueter et al. 2008).