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. 170 |