The widespread introduction of highly productive and rot-resistant forms and hybrids of aspen (Populus tremula L.) into the forest production is constrained by the lack of effective methods of their vegetative reproduction. Achievements of modern forest biotechnology enable in vitro cloning of economically valuable aspen genotypes and obtain planting material for plantation forest growing. The study of the manifestation features of valuable traits and genetic stability of in vitro clones propagated in the field (ex vitro) is important for the development of effective and reliable propagation methods that guarantee the preservation of the genetic and economic value of parent trees for their sustainable and targeted reproduction. The results of genetic stability evaluation, growth dynamics, productivity and wood quality of three in vitro propagated aspen clones (6/3, 15/01, and 20/4) in the field are presented. Micropropagation was carried out by direct organogenesis using hormone-free nutrient media. According to the results of 17-year field trials, clones demonstrate good growth and sufficiently high productivity of stands; preserve the growth characteristics of parent trees, showing no signs of somaclonal variability. At the age of 17, the average height of the trees was 18–20 m; the trunk diameter was 25–30 cm; the trunk volume was 0.391–0.553 m3; the timber volume was 111–227 m3/ha at trees placing 4×4 and survival rate 44–71 %. High genetic stability of clones in vitro and ex vitro was revealed based on the results of analysis of microsatellite loci, ploidy level and mixoploidy. It is shown that the triploid clone 15/01, which has high myxoploidy level, is characterized by a higher preservation and better wood quality attributes (wood density and fiber length) than diploid clones. This is probably due to the optimal balanced ratio of cells with different ploidy levels (triploid, diploid, and aneuploid), which provides the most effective expression of genes in specific environmental conditions.
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Author Name: O.S. Mashkina, E.A. Shabanova, I.N. Varivodina, T.A. Grodetskaia
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Keywords: Populus tremula L., in vitro cloning, field trials, chromosomal and microsatellite analysis