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close this bookMedicinal Plants: Rescuing a Global Heritage (WB, 1997, 80 p.)
close this folder1. The global background
View the document(introduction...)
View the documentEconomic issues
View the documentPolicy issues
View the documentRegulatory issues
View the documentSocial issues
View the documentConservation Issues
View the documentAgricultural issues
View the documentForestry issues
View the documentVeterinary issues
View the documentThe international research base

Agricultural issues

For many medicinal plants, cultivation is the main hope for maintaining supplies at today's levels. The wild resources are decreasing, the supply fluctuating in an unstable manner, the quality control is inadequate. Additionally, the botanical identification of the specimens is often suspect-sometimes because of fraud and other times because of genuine mistakes. Different species of plants (with wholly different chemical constituents) often look alike to the person handling the dried materials, and even sometimes to the gatherers themselves. The people handling the samples may he unreliable, and the chances for adulteration are legion.

Through the process of cultivation, the various plants can be increased on a controllable and sustainable basis, the quality can be better assured, the species identification made secure. In addition, there are possibilities for improving the crop genetically based on the level and mix of ingredients that have the medicinal effects. Yields can be manipulated by agronomic means, such as fertilizer and pest control. Finally, the handling of the materials can be regularized and the possibilities of adulteration reduced.

But all of this is mostly untapped as yet. While the domestication and cultivation of medicinal plants is several thousand years old, it is apparent that most agriculture ministries in developing countries play little role in cultivating medicinal plants. The present source of the raw materials for the pharmaceutical industries, traditional health practitioners and family users is met basically from wild sources, including places such as field borders, marginal, remote, and waste lands where the wild vegetation is left to grow unattended. The demand is also met by cutting forest trees or uprooting herbs and shrubs on nominal payment or on an unauthorized basis. A much greater awareness needs to be created among agriculturists that cultivation is the primary means of reversing the impact of unsustainable harvesting practices of wild populations.

Palevitch (1991) compared collection versus cultivation for eight important considerations. In light of the continuing loss of biodiversity, the relative advantage of cultivation is even more pronounced. While millions of dollars are invested in supporting food and other crops, little is spent on supporting the world's medicinal-plant resource base. Nevertheless, isolated medicinal-plant breeding programs have already produced a number of high yielding cultivars.

The efforts of the medicinal-plant breeder should be aimed at increasing the final yield of the active compounds and enhancing the metabolic functions that result in their accumulation. There will be difficulties as our knowledge of medicinal-plant genetics and physiology is poor, and we know less about the biosynthetic pathways leading to active ingredient formation for which these plants are valued. Another difficulty is that perhaps certain subsidiary compounds must also be present for the herbal cure to be effective.

An especially inhibiting factor in the breeding research is the variability of medicinalplant populations. Many populations found in their natural habitats are not balanced in terms of chemical characteristics and active compounds. Selective breeding of medicinal plants may follow several lines, including: random selection in populations; landraces with specific chemical characteristics; selection of clones; and hybridization. Commercial cultivation of medicinal plants demands strong and continuing attention to these diverse fields.

The farming of medicinal-plant is coming into a new stage of development that could lead to it becoming a major employer of local labor and an instrument to poverty alleviation in the developing countries. The efficiency and success of medicinal-plant cultivation will depend on the productive ability of plant material and collaboration between researchers and local peoples to enhance and sustain that production. Basic questions that need answers include:

· Is the plant suitable for cultivation?
· What are its ecological and agronomic requirements (light, moisture, soil, etc.)?
· Does it tolerate intra- and interspecific competitors?
· What insect pests, and plant pathogens are likely to attack it?
· Will harvesting be a problem?
· How well will it store without loss of therapeutic activity?
· Can it be easily processed (purified, packaged, and shipped without losing efficacy)?