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Differences in growth, wood density and wood anatomy in Norway spruce genotypes, and development of height and autumn frost hardiness in their seed offspring

The main aim of this work was to study the magnitude of phenotypic variation in different growth, wood density (WD) and wood anatomy properties, and correlations between these, in 41-year-old clones and provenance hybrid clones of Norway spruce (Picea abies (L.) Karst.). Additionally, the development of height and autumn frost hardiness in their seed offspring, under different temperature and/or atmospheric CO2 concentration treatments, were studied under greenhouse conditions over one growing season. Local Finnish clone V43, and two Finnish–German V449 and V381 provenance hybrid clones had higher stem volume than the average of the 25 genotypes included in the study (Paper I). They had also relatively high overall WD compared to the average of all the genotypes. The geographical transfer of father parent trees affected the overall WD. The averages for tracheid length, double cell-wall thickness (2CWT) in both earlywood (EW) and latewood (LW), and lumen diameter in LW, differed in five genotypes selected for detailed analyses of wood anatomy (Paper II). These parameters and the number of rays correlated with the widths and wood densities of EW and LW. The 2CWT of the tracheids closest to resin canals differed from that in the normal tracheids (Paper II). These differences may be partly affected by the origins of the genotypes. Under greenhouse conditions, elevated temperatures increased the height growth in seedlings. It delayed the onset of autumn frost hardiness development and shortened its duration. Elevated CO2 did not affect the development of height and frost hardiness. None of the genotypes showed both superior growth and frost hardiness (Paper III). A need for further studies on wood anatomy – for example, to consider genotype-specific variations in structural compounds – emerged based on this work. The obtained understanding of phenotypic variation in different genotypes may provide support for tree breeding in the future.