Forest genetic resources
Neem, Azadirachta indica A. Juss. (Meliaceae), is an evergreen, multipurpose tree species native to the Indian sub-continent and south-east Asia where it has been traditionally used for centuries. The species adaptation to hot and dry climates has made it one of the most commonly planted species in arid and semi-arid areas, both within its natural range and outside, in Africa, Latin America and the Caribbean. In the African Sahel, neem is mainly planted as shade tree and in windbreaks, although production of fuelwood by pruning and use in local pharmacopoeia are important. In its natural range, particularly in India, products derived from neem have been widely used for centuries for many medicinal and pest management purposes. Fruit are particularly rich in azadirachtin and other pesticide compounds.
Several public organizations, private corporations, non-governmental organizations (NGOs) and individuals are promoting the development of research on neem and its cultivation in various ecological conditions. Extracts of neem oil and chemicals for industrial uses are gaining more and more attention worldwide. Much work has been carried out on the characterization and utilization of neem natural extracts and chemical compounds, on testing their pesticide properties, on the potential for cultivation of the species in many developing countries, and on extending its utilization by local farmers and rural communities.Despite the widespread use of neem, global programs for the evaluation and improvement of the genetic resources of the species were not initiated before 1994, mainly because of seed storage and transport problems which placed a serious constraint on seed collection and transfer. As a result, the genetic material found in plantations is generally thought to have been originally chosen in an empirical, restricted manner, and its genetic base is frequently likely to be very narrow, particularly in countries located outside the natural range of the species. Neem decline has affected many Sahelian countries in the 1990s for which a number of interacting environmental and genetic factors have been alleged, possibly aggravated by pathogens.
While neem has a potential for domestication and utilization at a wider scale as a crop tree, knowledge about the extent and pattern of genetic variation, inside and outside its natural range, is scarse and fragmented. It is important to keep in mind that, besides its pesticide properties, neem is a multipurpose species which is widely used for environmental conservation and restauration, including soil amelioration and the provision of shade, and as ornemental tree.
Azadirachta indica tree with fruit, Burkina Faso. Photo: Roberto Faidutti
More information on neem tree genetic diversity is available at the International Neem Network (INN) homepage.