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ŠUMARSKI LIST 1-2/1966 str. 62     <-- 62 -->        PDF

(2) collect the seed from trees selected as representatives of all degrees
of the variation series in proportion to their frequencies if it is desired to
preserve the natural variability of the population, otherwise only from plus
trees. For the already mentioned reasons we recommend the first-named
(3) collect the seed from a sufficient number of trees retained for the
preservation of population variability in the progenies. We lack concrete data
for drawing a conclusion about the minimum number of trees. In view of the
heterozygous character of the most genotypes of forest tree populations, we
might conclude that the gene pool of individual trees is large, that great
variability appears already in the progenies of the individual trees of the
population, and that the population gene pool could be preserved ammong in
the progenies of a relatively small number of parent trees. Falconer´ s
data (1960) indicated that in half-sib families the degree of inbreeding attains
the value of F= l only within twenty generations and that the greatest decrease
in variability occurs in the first generations (10—12,5%). Yet, lacking concrete
experimental data, it is necessary to observe the practice of collecting seed from
at least 10—15 selected representatives of a population. We should mention
that for the study of provenances the seed should be collected from 10—25
trees of a population (C a 11 a h a m 1964).
Two methods could be used for the selection of seedlings germinated from
the seed collected in a population:

(1) select the best seedlings;
(2) select the individuals by random sampling.
The first method should enable us to preserve the »better« portion of the
population. Such a principle is usually applied in provenance tests. In the
selection of young plans this is very unsafe. Using to the second method, one
should select the seedlings at random in the needed number from all the
variability degrees in proportion to their frequencies. We make these recommendations
for preservation of as complete a range of genetic variability of
the population as possible. We consider this the only correct method, especially
if we deal with the selection of very young plants.

The selection of individuals or groups as representatives of the gene pool
of natural forest tree populations would be possible after a knowledge of the
genetic variability (races) on the basis of the phenotypic expression of genetically
related and economically important characters. Although botanical-
systematical studies of varieties and genetic studies of races offer insight into
the variability of some more important forest tree species, available data on
variability of most forest tree species are still too limited to enable one to select
genetic material of the more significant races. A complete knowledge of the
genetic variability of the populations of individual forest tree species which
would render possible a separation of the geographical and ecological races
would take so long to attain that selection of the hereditary material of the

natural forests is an urgent task, especially if we consider how rapidly they are
destroyed by man.

The only possible solution to the problem of how to select is therefore to
use the results of previous investigations of botanical varieties, population
variabilities, provenance studies, and to avail oneself of forest inventory data