158 • Impacts of Applied Genetics — Micro-Organisms, Plants, and Animals 
variety dominates the planting of a crop, there 
is some loss of genetic variability, the resulting 
uniformity causes crop vulnerability— and the 
displacement of indigenous varieties— a real 
problem. 
The rate of adoption of HYVs levels off below 
100 percent in most countries, mainly because 
of the numerous factors affecting supply and 
demand:^^ 
• supply factors: 
—the present HYVs are not suitable for all 
soil and climatic conditions; 
—they require seeds and inputs (such as 
fertilizers, water, and pesticides) that are 
either unavailable or not fully utilized by 
every farmer; and 
—in some regions, a strong demand still ex- 
ists for the longer straw of traditional 
varieties. 
• demand factors: 
—consumers may not prefer the HYVs over 
traditional food varieties; 
—Government price policies may not en- 
courage the production of HYVs. 
For these and other reasons, countries already 
using a great deal of HYVs will continue to adopt 
them more slowly. 
Six factors affecting adequate 
management of genetic resources 
1. Estimating the potential value of genetic re- 
sources is difficult. 
Of the world’s estimated 300,000 species of 
higher plants, only about 1 percent have been 
screened for their use in meeting the diverse 
demands for food, animal feed, fiber, and phar- 
maceuticals. Genetic resources not yet col- 
lected or evaluated are valuable until proven 
otherwise, and the efforts to conserve, collect, 
and evaluate plant resources should reflect this 
assumption. This point of view was strongly re- 
“D. G. Dalrymple, Development and Spread of High-Yielding Vari- 
eties of Wheat and Rice in the Less Developed Nations, 6th ed. 
(Washington D.C.: U.S. Department of Agriculture, Office of Inter- 
national Cooperation and Development in cooperation with U.S. 
Agency for International Development, 1978). 
Mvers, "Conserving Our Global Stock," Environment 
21(9):25, 1979. 
fleeted in a 1978 recommendation by the Na- 
tional Plant Genetic Resources Board. It’s recom- 
mendation was that four major areas of genetic 
storage— collection, maintenance, e\aluation, 
and distribution— be viewed as a "continuum 
that sets up a gene flow from source to end 
use’’.^“* 
2. The management of genetic resources is com- 
plect and costly. 
The question of how much germplasm to col- 
lect is difficult and strongly influenced by cost. 
Thus far, only a fraction of the ax ailahle di\ ersi- 
ty has been collected. A better scientific undiM’- 
standing of the genetic makeup and pre\ ious 
breeding history of major cro|)s will help deter- 
mine just how much germplasm should he col- 
lected. Efforts to gi\e priorities for coIUu’tioiH* 
have been hindered by the scientific ga[)s in 
knowledge about what is presently stored 
worldwide. And while attempts ha\e been 
made to estimate the economic return fi’om in- 
troduction of specific plants (see table 28), the 
degree to which agricultui'al production and 
stability are dependent on generic \ai'iahility 
has not been adetjuately analyzc'd. 
Evaluation of genetic characteristics must he 
conducted at different ecological sit(\s by multi- 
disciplinary teams. The data ohtaiiK'd w ill only 
be useful if adetiuately assessed and made a\ ail- 
able to the breeding community (see l ech. Note 
14, p. 163). 
Germplasm must he adec|uately maintained to 
assure viability, "woi’king stocks" must he made 
available to the breeding community. Hu‘ |)i’i- 
mary objective of storing geriii|)Iasm is to make 
the genetic information axailahle to hreedei.s 
and researchers. 
3. How much plant diversity can he lost without 
disrupting the ecological balances of natural 
and agricultural systems is not known. 
^■‘Kepoft to the Sc( rcliiry ol Vgrit iillurr b\ ihi- \--.iNl.ini '«•< 
retarv lor (:ons(*r\ alion. Rc.-icarch, .iiid l.dm .ilioti b.i'-i-d on llii di- 
liberations and r(>commi‘ndalions National I'lanI ta-nelii III 
sources Boaril. July 1978 
^“Secretarial, International Ho.ird Ini' I’lanI (a-ncin Kcjmc.i 
Annual Report 197/i, Rome, ( onsullalne (.roup on Inlcmalu' .al 
Agricultural Research. I!)7i) 
