154 • Impacts of Applied Genetics — Micro-Organisms, Plants, and Animals 
Genetic variability; crop vulnerability; and 
storage of germplasm 
Successful plant breeding is based on tbe 
amount of genetic diversity available for the in- 
sertion of new genes into plants. Hence, it is 
essential to have an adequate scientific under- 
standing of how much genetic erosion has taken 
place and how much germplasm is needed. Nei- 
ther of these questions can be satisfactorily an- 
swered today. 
The amount of genetic erosion that 
has taken place 
Most genetic diversity is being lost because of 
the displacement of vegetation in areas outside 
the United States. The demand for increased 
agricultural production is a principal pressure 
causing deforestation of tropical latitudes (see 
Tech. Note 11, p. 163), zones that contain exten- 
sive genetic diversity for both plants and 
animals. 
It has been estimated that several hundred 
plant species become extinct every year and 
that thousands of indigenous crop varieties 
(wild types) have already been lost. However, it 
is difficult to measure this loss, not only because 
resources are on foreign soil but because ero- 
sion must be examined on a species-by-species 
basis. In theory, an adequate evaluation would 
require knowledge of both the quantity of di- 
versity within a species and the breadth of that 
diversity; this process has in practice, just be- 
gun. What is known is that the lost material can- 
not be replaced. 
The amount of germplasm needed 
Germplasm is needed as a resource for im- 
proving characteristics of plants and as a means 
for guaranteeing supplies of known plant 
derivatives and potential new ones. Even if 
plant breeders adequately understand the 
amount of germplasm presently needed, it is dif- 
ficult to predict future needs. Because pests and 
pathogens are constantly mutating, there is 
always the possibility that some resistance w ill 
be broken down. Even though genetic dix ersity 
can reduce the severity of economic loss, an epi- 
demic might require the introduction of a new 
resistant variety. In addition, other pressures 
will determine which crops will lie grown for 
food, fiber, fuel, and pharmaceuticals, and how 
they will be cultivated; genetic dixersity x\ ill he 
fundamental to these innovations. 
Even if genetic needs can he ade(|uately iden- 
tified, there is disagreement about how much 
germplasm to collect. In the past, its collection ' 
has been guided by differences in moriihologx’ 
(form and structure), xx hich hax e not often been 
directly correlated to breeding ohjectixes. I'ui'- 
thermore, the extent to xx hich the nexx gcMUMir 
technologies xvill affect genetic xariahility, xiil- 
nerability, or the storage of germplasm, has not 
been determined. (See apji. Il-A.) 
In addition to its uses in plant improx cment. 
germplasm can prox ide both old and nexx piod- 
ucts. Recent interest in gioxx ing guax ule as a 
source of hydrocarbons (for ruhhei-, energ^v 
materials, etc.) has focused attention on plants 
that may possibly he undei’utilized. It has been 
found that past collections of guaxule gei iii- 
plasm haxe not been ade(|uatelx maintained, 
making current genetic improx cnK'iits more dil- 
ficult. In addition, half of the world's medicitial 
compounds are obtained from plants: maintain- 
ing as many xarieties as possible would ensure 
the ax ailaliility of compounds known to he use- 
ful, as xvell as ntnv, and as xot u nd i.s( ox e red 
compounds— e.g., the (|uinine drugs used in the 
treatment of malaria xvere originally obtained 
from the Cinchona plant, ,\ USD \ collection ol 
superior gei’mplasm (‘stahlish(>d in 1!M0 in 
Guatemala xvas not maintained \s a conse- 1 
