DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu




ŠUMARSKI LIST 1-2/1966 str. 131     <-- 131 -->        PDF

that it is in this hybrid progeny that heterotic individuals are most likely to
be found. The progeny which had the highest mean height (1) has a small
variability and the hybrid progeny form the cross P. pyramidalis x P. nigra
varied least.


At the same time, however, within the same section Aigeiros a cross
between the American P. angulata and European P. nigra offers the greatest
chance of obtaining heterosis.


When breeding for trees which will be later propagated vegetatively it
is necessary to aim at producing a small number of heterotic individuals,
which could be used as new cultivars. Under these conditions the widest
possible variability in the characters of economic interest is desirable. The
result obtained with P. angulata x P. nigra is all the more interesting since
it appears to be analogous to the excellent results obtained with the Euroamerican
poplars (P. deltoides x P. nigra).


CONCLUSIONS


1. On the basis of the available data it is difficult as yet to establish a
definite relation between the parental affinity and the heterosis of the
progeny, however, it does appear that this relation has no simple dependence
on the systematic position of the parents.
2. Within a systematic unit (species or section), heterosis among hybrids
appears to be greater the greater the heterogeneity of the parental forms.
3. This heterogeneity is best explained by the geographic isolation of the
parental sites of origin which presumably have different ecological conditions,
and also — as can be seen from the literature — other isolating factors can
play a role here.
4. In the subgenus Eupopulus a greater degree of heterosis can be
obtained in the intrasectional hybrids between parents of distant provenances
than in intersectional hybrids between sympatric parents.
5. In the subgenus Leuce the results are not as clear cut, since hybrids
between the sections Albidao and Trepidae often show considerable heterosis
in spite of the fact that the parents are sympatric.
UTJECAJ RODITELJSKOG AFINITETA NA STUPANJ IIETEROZISA
KOD HIBRIDA TOPOLA


Zaključak


1. Na osnovi raspoloživih podataka teško je zasada utvrditi tačno određen odnos
između roditeljskog srodstva i heterozisa potomstva. Međutim .izgleda da taj odnos
nije u jednostavnoj ovisnosti o sistematskom položaju roditelja.
2. Unutar sistematske jedinice (vrsta ili skupina) izgleda da je heterozis između
hibrida to veći što je veća heterogenost roditeljskih formi.
3. Ta heterogenost se može najbolje objasniti geografskom izolacijom roditeljskih
staništa porijekla koja vjerojatno imaju različite ekološke prilike, a također —
kao što je vidljivo iz literature — ovdje mogu igrati ulogu i različiti drugi izolirajući
faktori.
4. Kod podroda Eupopulus veći stupanj heterozisa može se dobiti kod unutarskupinskih
hibrida između roditelja udaljenih provenijencija, nego kod međuskupinskih
hibrida između roditelja istog područja rasprostranjenja.
5. Kod podroda Leuce rezultati nisu tako jasni budući da hibridi između skupina
Albidae i Trepidae često pokazuju heterozis usprkos činjenici da su im roditelji s
istog područja rasprostranjenja.