Giant leucaena (Leucaena leucocephala subsp. glabrata): a versatile tree-legume for sustainable agroforestry

Leucaena leucocephala (leucaena) is one of the 22 Leucaena species that originated in Central America. There are two major subspecies of leucaena, L. leucocephala subsp. glabrata (giant leucaena) and L. leucocephala subsp. leucocephala (common leucaena). Giant leucaena is a medium size fast-growing tree important for agroforestry while common leucaena is a small bushy shrub that is considered to be an invasive weed. Giant leucaena can be grown as a woody tree of up to ~ 20 m in height or maintained as a bushy fodder legume by repeated harvest of its foliage several times a year. Giant leucaena grown for fodder can produce forage dry mater yield of up to 34 Mg ha−1 year−1. High forage yield together with high protein content makes leucaena an ideal fodder legume for the tropical and subtropical regions of the world. Although mimosine present in the leucaena foliage has toxicity, it should not be a big concern because ruminants can be successfully inoculated with the mimosine-metabolizing rumen bacterium Synergistis jonesii. Alternatively, mimosine present in the leucaena foliage can be removed easily and inexpensively through simple processing. Giant leucaena cultivars are generally free from diseases and are highly tolerant to drought. Although infestation by psyllids may be a problem, a number of psyllid-resistant cultivars of giant leucaena have been developed through interspecies hybridization. The wood of giant leucaena can be used for timber, paper pulp, or biofuel production. Leucaena foliage and wood may serve as raw materials for development of new industry for production of phytochemicals such as mimosine, tannins and anthocyanins, wood products, and high-protein animal feed for farm animals in the future.