DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 60     <-- 60 -->        PDF

resistance to frost, drought, may later be required, although they are not
considered very significant at present. The requirements will depend both on
the development and needs of the wood-processing industries. It may happen,
for instance, that some of the qualities considered today as poor ones will be
in great demand in the future, as for instance a great quantity of branchwood.
Besides, there is the possibility that some of the poor trees also possess the
required genes, but in such combinations that these genes are concealed
(Syrach La r sen 1958). Therefore, if the gene pool of natural forests is
selected only on the basis of the characters which are today of economic
importance we will not act correctly. We want to preserve the gene pool for
the future, for future needs, and therefore we must maintain it in its natural
variability. Only thus can we hope that the material selected on the basis of
the qualities required today will potentially possess those characters which
may be required in the future.


CRITERIA FOR THE SELECTION OF THE GENE POOL TO BE
PRESERVED


In the selection of the genetic material of natural forests for preservation
the main problems are:


— what to select,
— how to select,
— how much to select.
If we discuss the problem »what to select«, we should point out that the
basic principle ought to be: selection of the hereditary material with the best
expression of genetically related and economically important characters. But
having in view also possible future needs which today are still unpredictable,
the leading principle should also be to preserve the natural variability in the
highest possible degree.
The next problem selection is: whether to preserve the hereditary material
in the form of individual population genotypes, i.e. in the form of plus trees
or elite trees, or in the form of group representatives of populations,
Plus trees are most often selected as parent trees for hybridization. In
fact, the preservation of the gene pool has a similar objective: to make possible
its reproduction and thereby also its improvement. Accordingly, in preserving
the gene pool we are also taking into consideration the selection of individual
representatives of the population. But if we take into account the already
stressed need to preserve the genetic resources of natural forest in their full
variability, then preference should be given to the selection of group representatives
of populations. Inclusion of a greater number of genotypes of one
population will preserve far more complete variability, and gene frequencies,


i.e. all the typical heritable characteristics which, in fact, represent the gene
pool of one population. The decision about the selection of the individual or
group representatives of populations will depend on the form and type of the
planting in which we wish and are able to preserve the hereditary material.
Another problem of interest is the question of how and what to select
under the assumption of one or other decision. If individual representatives
are chosen, selection might be guided by the following principles: if only one
representative is selected, it should be selected either (a) among individuals
that are the best by their phenotypic expression of the genetically related