Genetic diveristy and breeding of larch (Larix decidua Mill.) in Romania

Although it is one of the most important coniferous species, the larch(Larix decidua Mill.) covers a restricted area in Romania, only 0.3% of the forest area, most being represented by artificial stands. The natural area of the larch is fragmented, being concentrated into five genetic centers: Ceahl u, Ciucas, Bucegi, Lotru and Apuseni. The speed of growth, high productivity, high wood quality and resistanceto adversities resulted in initiating research on the genetic variability of the larch. In 1978 and 1982 respectively, by means of international collaboration, two series of comparative trials were installed, with Romanian and foreign provenances of larch, totalizing 6 experimental areas. Selection of seed stands followed, andamong them, more than 300 plus trees. There have been installed 26 orchards (134 hectares) of which 3 (15 hectares) are interspecific seed orchards (Larix x eurolepis).This paper presents the results obtained over the last years, regarding the continuing larch breeding program; genetic variation of the main characters in multisite provenances comparative trials planted in 1982, evaluation of the genetic parameters in a clonal seed orchard in order to advance to the second generation seed orchard, and a study of the genetic diversity by means of primary biochemical markers. The provenance tests include 24 populations of larch, 13 Romanian and 11 from the following countries: Germany (4), Austria (2), Belgium (1) and the Czech Republic (4). The studied characters are total height, diameter at 1.30 meters, volume/tree, branches characters, stem straightness and survival. At the age of 25 years from planting, the variance analysis reveals significant interpopulation genetic variation for all the studied characters. The expected genetic gain and the genetic parameters, estimated inthe Adancata larch seed orchard, shows that selection on the clones level, in the first generation seed orchard, can be successfully applied, being effective from both genetic and economic point of view. The broad-sense heritability coefficients for diameter breast height (h2 = 0.773), branch thickness (h2 = 0.759), angle of insertion(h2 = 0.775) and stem form (h2 = 0.591) indicate a strong genetic control for these characters. The expected genetic gain by means of selection of the best 10 clones ranges between 16 to 36%, depending on the character considered. The study of genetic diversity, based on the izoenzymatic markers in provenances comparative trials of larch indicates a high level of intrapopulation genetic diversity, especially for populations loc