Theoretical prerequisites for the creation and some practical results of studying the birch gene pool in the Voronezh region

In accordance with the National Goal "Environmental Well-being", 17 directions have been formulated and justified in which research is being conducted and is planned to be conducted at ex situ birch F1 and F2 fa-cilities. The variability of height growth of seed progeny and self-pollination on productivity (height growth) and survival in the early stages of ontogenesis in introduced birch species, Manchurian birch (Betula mandshurica (Regel) Nakai) – diploid, 2n=2x=28, poplar-leaved birch (Betula populifolia Marshall) – diploid, 2n=2x=28 and elm–leaved birch (Betula ulmifolia Cham.) - hexaploid, 2n=6x=84 were studied. The interest in these species is caused by the fact that they are diverse, the elm-leaved birch has 6 haploid chromosome sets. Since the survival rate of seedlings is one of the main characteristics in the creation of forest crops, an analysis of the preservation of elm-leaved birch (Betula ulmifolia Cham.) trees was carried out, 50% with self-pollination and 81.25% with open pollination. A brief history of the terminology of these species, the variability of their productivity signs are given on the example of growth at two, three, four, five and six years of age, as well as the preservation of some of them. The phenomenon of "reverse" inbreeding depression has been revealed for a polyploid introduced spe-cies of B. ulmifolia. The revealed variability in the leading type of growth of the reproduction system in these introduced birch species shows the prospects of breeding work with polyploid species – B. ulmifolia.