DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 172     <-- 172 -->        PDF

The Institute for Forestry and Timber Industry, Beograd, carried out a controlled
hybridization of the native Walnut and Black Walnut, which show signs of
heterosis.


3. Hybridization of Poplars and Willows
In this country most efforts have been expended on the hybridization of the
genus Populus.


The Forestry Faculty, Beograd, was among the first to begin work on the hybridization
of Poplars in 1957 (26, 27, 30, 31, 32). Performed were crossings between
different species of Poplars. In the period 1957—1960 was produced a total of
57,298 hybrid plants. Through controlled hybridization in water cultures and on standing
trees, 05 combinations with 28,490 hybrid plants were produced, while by
using the seed from spontaneous and subspontaneous hybridization 29,808 hybrid
plants from 11 combinations were obtained. As female parents were used 25 Poplar
forms and as male parents 19 forms, i. e. a total of 44 forms. Of this number there
belong to the section Aegeiros 34 forms and to the section Leuce 10 forms. On the
basis of the height and diameter increments, stem straightness arrangement of lateralbranches,
resistance to diseases, ease of rootability of cuttings, and the assimilating
surface, chosen were only 26 clones for further cultivation and investigation.
Of these, 14 clones produced at the end of the first year a greater height and diameter
increment than the standard type Populus euramericana cv. robusta.


The Poplar Institute, Novi Sad, started with these works in 1961, and carried
out were mainly interspecific crossings in Poplars and Willows, After the poor results
of controlled crossing of Black Poplars with European — American hybrids
(x scrotina, x robusta, x marilandica) work was continued with controlled crossing
of Populus nigra (native) x P. deltoides.


In the Poplars from the section Leuce were carried out in the main controlled
interspecific crossings: Populus alba x P. grandidentata, P. canescens x P. grandidentata,
P. alba x P. tremuloides, P. canescens x P. tremuloides, and P. tremula x


P. tremuloides, which gave good results. To a lesser extent were made crossings of
P. alba x P. tremula, P. canescens x P. tremula, and P. tremula x P. tremula (remoteraces).
The first steps in the controlled crosing of Willows were made in 1964. This
work aims at obtaining interspecific hybrids between the arborescent Willows, i. e.:
Salix alba x S. nigra, S. alba x S. sachalinensis. The results achieved were satisfactory.
Realized were more than a hundred combinations and raised 10,000—15,000
hybrid plants yearly. The collection of seeds from spontaneous pollination began in
1956: The seed is collected from plus trees of Leuce-Poplars and from Willows.
From this seed are produces ca. 10,000 spontaneous hybrids.


The Institute for Dendrology and Genetics of the Forestry Faculty, Zagreb,
carried out in 1964. controlled crossing of Salix fragilis x Salix alba. Besides, progeny
was also produced by spontaneous and subspontaneous hybridization of Salix
alba.


From what precedes visible that the experiments and practical work on the
crossing of Poplars are considerably developed and has already been productive
of results.


V. INVESTIGATIONS ON THE OCCURRENCE OF MUTATIONS
Also in this field the work has been started with the aim to induce mutations
artificially. In this country, in nature, no mutations have been found so far, but
there are indications for their existence so that attempts should be made to discover
them.


1. Application of ionizing radiations
Experiments for inducing artificially the hereditary changes have been made by
the action of gamma rays and radioactive phosphorus on seed material, pollen, gametogenesis
stages, cuttings etc.


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