The "Alfalfa of the Tropics"
This web resource strives to gather and disseminate much of the available information on Leucaena. It provides active links to historical literature, seed resources, ongoing research activities from numerous research groups, as well as the ability to get additional publicity for your lab's website. Please just contact us, and we'll be happy to add your information!
Though most are familiar with well know crop species (e.g., corn, rice, wheat, etc) many lesser-known plant groups are also of tremendous significance, yet these receive comparatively little research attention or funding. Several such plant groups are broadly known as “multipurpose crops” that are widely employed for a variety of uses, including: fruits and vegetables in the human diet, as animal feed, shelter, soil stabilization and fertilization, fuel, or even bioactive compounds. These are often key elements in integrated approaches to sustainable agriculture in impoverished regions, where they can support the production of mainstream cereals or other crops. One such lesser-known multipurpose crop is the mimosoid legume genus Leucaena, which comprises 24 species of nitrogen-fixing trees and shrubs with a natural distribution centered in Mesoamerica.
The genus is remarkable for a number of reasons, not the least for the discovery of Leucaena pod and seed remains in archaeological sites alongside maize and squash remnants dating to ca. 6000 years ago. Trees of Leucaena species were cultivated and incipiently domesticated as food plants in parallel with the mainstream maize – bean – squash crops that formed the basis for the development of agriculture in Mesoamerica. The use of Leucaena seeds and fruits for food remains largely restricted to Mexico, but large-scale plantations and smaller holdings are found pantropically. These introduced plantations, particularly of L. leucocephala, provide: 1) unique protein-rich leaves for animal feed in small and large-scale livestock production systems, 2) green manure used as nitrogen-rich fertilizer for crops and for soil stabilization in alley-cropping systems, and 3) rapidly renewable woody biomass for construction, fuelwood, and even biofuels through lignocellulosic precusors. As a result, Leucaena represents a critical component of many integrated sustainable farming systems on a variety of scales in the tropics and considerable time and effort have been spent accruing seed resources for all species and on the development transformation tools.
Unfortunately, the limited availability of molecular markers and genotype/expression data necessary for effective germplasm selection and improvement programs, as well as problems caused by a defoliating psyllid pest, Heteropsylla cubana, mean that the full potential of Leucaena as a multipurpose crop has not being realized. Psyllid pests, native to the natural range of Leucaena, spread across the introduced range of the genus in the 1980s, resulting in cyclical defoliation and stunted growth causing serious problems for those relying on Leucaena as a multipurpose crop. The severe impact of these pests has largely been attributed to lack of natural psyllid predators outside of the native range and a narrow genetic base and monoculture approaches applied in Leucaena cultivation.