Genetic variation and phenotypic plasticity of Quercus robur populations and open-pollinated families in Lithuania

The purpose of the study was to estimate among- and within-population variation for juvenile growth and for growth rhythm traits, bud flushing and leaf colouring, in open-pollinated families of Quercus robur L. from six Lithuanian populations under different environmental conditions. Assessments were done in the nursery up to 4 yrs, and after replanting in three field trials at the age of 6 yrs. A highly significant population effect was found for bud flushing. Large family variance components were estimated for bud flushing and height. The familyxsite interaction was significant and more pronounced for growth cessation and height than for bud flushing. Depending on the trait, from 13 to 33% of families contributed significantly to the familyxsite interaction. Strongly significant sitexpopulation interaction was estimated only for bud flushing. Families with early bud flushing were taller, although the correlation was weak. Correlations between family means in bud flushing and bud flushing of parent trees varied from 0.53 to 0.60. Large CV A estimates for the adaptive traits suggest that species have a potential to adapt to environmental changes that may occur from global warming and indicate good perspectives for gene conservation and tree breeding when using Multiple Population Breeding System.