Legumes are the second crop group contributing to human sustenance, following only to cereal grains as a source of calories (FAO 2006). With a total global production exceeding 30 million tons, peanuts (Arachis species), in particular, are an important source of dietary protein in many developing nations, and provide an important source of oil for cooking and fuel. Biological fi xation of nitrogen makes legumes an important crop for improving soil fertility and an important part of many crop rotations.