The Development and Regulation of Soybean Nodules

Legumes represent the third largest family of angiosperms, with > 18,000 species worldwide (Leguminosae or Fabaceae). Due to their high nutritional value, they have been cultivat‐ ed by many cultures for use in agriculture. Indeed, legumes currently represent some of the most important food, feed and fuel crops grown around the world, second only to cereals. They have a global-production value of > $200 billion per year and are cultivated on 12–15% of the world’s available, arable land (Graham and Vance 2003; Peoples et al., 2009; Jensen et al., 2012). Collectively, ~247 million tons of legumes are produced each year, and represent > 25% of the world’s primary crop production (Graham and Vance 2003; European Associa‐ tion for Grain Legume Research 2009). Some key legume crop species include: soybean, bean, pea, chickpea, cowpea, pigionpea and alfalfa.