Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Old colchicine-induced polyploid materials of Betula pendula Roth and Betula pubescens Ehrh. | 264s Ann. Sci. For. 1989 46 suppl. 264s-266s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Old colchicine-induced polyploid materials of Betula pendula Roth and Betula pubescens Ehrh. K. Pieninkeroinen and T. Valanne Department of Biology. University of Turku SF-20500 Turku Finland Introduction The members of the genus Betula form a particularly significant group of broadleaved trees in Eurasia and North America. Certain birch species . B. pendula B. pubescens and B. papyrifera are valuable sources of wood and great importance is attached to breeding work aimed at their economic improvement. Polyploidy induced by colchicine treatment in B. pendula and B. pubescens has been reported by Johnsson and Eklundh 1940 Schrock 1951 and Valanne 1972 . The rate of growth of induced Betula polyploids has been observed to be inferior to that of the diploid parental trees Johnsson 1956 Eifler 1955 1967 . It has also been reported that triploid B. pendula trees obtained from cross-pollination of colchicine tetrapioid and diploid trees did not grow faster than the diploid control plants Johnsson 1956 . The aim of this study was to reveal possible breeding and evolutionary trends in B. pendula and B. pubescens. Materials and Methods The material was part of about 2000 individually numbered ca 25 yr old B. pendula and B. pubescens trees which originated from extensive colchicine experiments with different birch species carried out in Finland Valanne 1972 The birches from the experiments are located on the island of Seili 60 12 N 21 55 E at the Experimental Station of the Finnish Forest Research Institute Punkaharju 61 43 N 29 25 E at Pâilahti by Drives 61 37 N 24 29 E and in the Botanical Garden of the University of Turku Ruissalo 60 26 N 22 10 E . From the materials of Punkaharju Drives and Turku 50 B. pendula and 50 B. pubescens trees were taken for this study. The chromosome counts were carried out according to the method of Hommo and Sărki-lahti 1986 using young
