Conservation and Sustainable Use of the Biosphere - WBGU

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Conservation and Sustainable Use of the Biosphere - WBGU

40 D The use of genetic and species diversity

substances for the development of medicines will be

reduced (Gettkant et al, 1997).

Every single plant species is potentially an interesting

candidate for such an examination since all

plants have developed chemical defence substances

against herbivores or pathogens that could in turn

prove effective in pharmaceutical terms. Mendelsohn

and Balick (1995) have calculated on this basis that,

of the approx 125,000 flowering plants in the tropics,

at least 375 potential medicines could be developed

with a saleable value of up to US$4 thousand million.

If we look at the relationships among the currently

known medicinal plants, we notice that the majority

come from a relatively small number of families

(Frohne and Jensen, 1998), which however represent

around one-third of all species worldwide. If only half

of these species can be used to develop an active substance

and we subtract the medicinal plants that are

already known, another 20,000 species would be

interesting in terms of their secondary metabolism.

However, once the gene has been extracted and put

into production for such substances, and the gene

expressed into other organisms (particularly

microorganisms) for industrial production, the

‘genetic donor’ could then fall back into obscurity

(Miller et al, 1995). The problems and opportunities

related to bioprospecting are discussed in detail in

Section D 3.3.

D 1.3.3.2

Food plants

In a similar way to medicinal plants, one could imagine

bioprospecting for plants that have particular

resistance features that would be important in cultivated

crops. This is less a matter of resistance to pest

organisms, since that generally involves specific

interactions between host and pest and can be combated

specifically through molecular changes in the

respective host-recognition systems. Complex resistances

are primarily a matter of tolerance to the

stresses of drought, salt and heavy metals that could

become important as a result of the expansion of

agriculture to marginal sites and the increasing salinization

in irrigated farming (Flowers and Yeo, 1995;

WBGU, 1995a). In the context of resistance to heavy

metals, good progress has been made by selection

within the crop species and not through transmission

of genetic information from related species. This can

change quickly, however, as more knowledge of the

molecular foundations of resistance is gained. In the

case of rice, however, most of the closely related

species are already being collected systematically in

order to cross-breed certain desirable features in the

future (Vaughan, 1994).

Food plants admittedly differ very much with

respect to their wild species base. However, these

wild forms are particularly important when breeding

for resistance to biotic and abiotic factors is concerned

(Cleveland et al, 1994). These resources are

not just acutely endangered because of the intensification

of land use, but also because of the concentration

in cultivation on a small number of high-yielding

varieties.This is aggravated by the fact that the industrial

high-performance varieties are not fertile and so

no further genetic development is possible. For

example, the whole soya production of the United

States is based on just six individual plants from a site

in Asia (Zedan, 1995). The farmer is no longer in a

position to produce his own seed. That means an

enormous supply risk under variable weather conditions

and in disaster-prone areas. With the trend

towards planting genetically modified species that

are not sterile and not – eg through polyploidization

– genetically distinct from the wild varieties, there is

an additional danger of the spread of characteristics

into the wild population through outbreeding and

the potential loss of genetic information in those

populations (WBGU, 2000a).The Biosafety Protocol

(Section D 3.2) is intended to respond to this and

other dangers.

It is also conceivable that new food plants will be

recruited and marketed out of the pool of around

75,000 edible species. The fruits of tropical plants are

particularly interesting in that respect, as are the

starch- and protein-storing tubers. However, the use

of plants in extreme habitats in which no agricultural

use is currently feasible (eg salty sites) could also

become possible (Myers, 1997).Whether these can be

domesticated – whether they can be improved

through targeted breeding for food production and

differentiate themselves genetically from their wild

forms remains an unknown at this stage (Diamond,

1998).

In essence, there are presumably over 10,000

species that could become food plants or have particular

stress-resistance characteristics that make them

interesting as a potential genetic resource for cultivation.

Presumably, however, in this case the search for

resistance features is more promising in related

species, so that the figure might have to be corrected

downwards. Once the genetic characteristics have

been harvested, however, the wild species might well

fall back into the insignificant group.

D 1.3.4

Harmful species

In contrast to certain animal species and to

pathogens, there is no species in the plant kingdom

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