DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 129     <-- 129 -->        PDF

between the hybrids and their parents being the result of age, and that the


same trees after several years may present a different picture as regards the


occurence of heterosis.


A review of the hybrids presented in Table 1 according to their taxonomic
groupings (after Dode 1905) permits to draw the following conclusions.


I. Subgenus Leuce
I. 1. Section Albidae — no data.
2. Section Albidae x Section Trepidae.
The natural hybrid P. x canescens Sm. displays according to the general
belief a heterosis with respect to both its parents. Satisfactory results were
obtained from the crosses P. alba x P. tremula and the reciprocal, however,
some authors criticize the view that these results indicate heterosis.


3. Section Trepidae
The crossing of P. tremula with P. tremuloides and reciprocally is
considered very promising with respect to the heterosis of growth and
resistance to some diseases (e.g. Venturia tremulae Aderh.) Several breeders
seek heterosis, with partial success, in the hybrids between the various
different provenances of P. tremula.


71. Subgenus Eupopulus
1. Section Aigeiros.
Hybrids carrying the general name of Euroamerican poplars originated
from the cross between P. nigra and P. deltoides. Many of them show heterosis
with respect to their parents.


2. Section Aigeiros x Section Tacamahaca.
The hybrids P. pyramidalis x P. simonii, P. angulata x P. berolinensis
and P. deltoides x P. trichocarpa gave good results as regards frost resistance
and fast growth.


3. Section Tacamahaca x Section Aigeiros.
Particularly the hybrids P. maximowiczii x P. pyramidalis, P. maximowiczii
x P. nigra, P. simonii x P. pyramidalis as regards their luxurious
growth, and P. suaveolens x P. pyramidalis as regards frost resistance, need
to be mentioned.


4. Section Tacamahaca.
The most successful and heterotic hybrids come from the breeding work
done by Schreiner and Stout (P. maximowiczii x P. berolinensis, P. maximowiczii
x P. trichocarpa). This same maternal tree yilds good results in crosses
with P. laurifolia. There are many more successful hybrids within this section.


This short review of the data presented in Table 1 should be supplemented
with information about hybrids which do not show heterosis. Data
on this subject are incomplete since the authors often publish only those
results of their works which have yielded successful cultivars. However, as
an example, some of the respective data are presented in Table 2.


The crosses between P. maximowiczii and P. berolinensis mentioned in
Table 2 were made in Körnik in 1950 and 1954, but gave poor results from
the economic standpoint, whereas similar crosses made by Schreiner and
Stout have produced some very valuable cultivars that are characterized by
heterosis with respect to the both parents. It is also interesting that the hybrid


P. angulata x P. laurifolia has produced no heterotic individuals, whereas the