Tropical Tree Legumes

Abstract

Legumes are members of the family Fabaceae, a diverse group of bean-pod bearing plants ranging from small annual herbs, through woody shrubs to giant perennial trees. Fabaceae is the third largest flowering plant family after orchids (Orchidaceae) and asters (Asteraceae), comprising around 700 genera and 20,000 species (Doyle and Luckow 2003). Fabaceae grow in a variety of soil conditions and growth habitats throughout the world, but predominantly in arid and also rain-fed tropical zones. The family is divided into the subfamilies Papilionoideae, Caesalpinioideae and Mimosoideae based on floral and other morphological characters. The Papilionoideae is the largest subfamily, with 476 genera and about 14,000 species (Lewis et al. 2003) and characteristic papilionaceous (butterfly-like) flowers (five petals are differentiated into two standards, two wings and one keel). This group of plants is mostly herbaceous, and includes cultivated crop legumes such as peanut (Arachis hypogaea), soybean (Glycine max), lentil (Lens culinaris), barrel medic (Medicago truncatula), French bean (Phaseolus vulgaris) and pea (Pisum sativum), which are rich protein sources in human and animal diets. The majority of the Caesalpinioideae and Mimosoideae are tropical or subtropical trees and shrubs.