Genetic variability of silver birch (Betula pendula L.) wood hardness in progeny testing at juvenile age.

摘要

Seventeen out of 24 Lithuanian and 2 Swedish silver birch (Betula pendula) populations were studied for wood hardness by using 6 J Pilodyn measurements. A total of 100 Lithuanian and 14 Swedish half-sib families at age 7 were being tested in the plantation, but only 83 local families were included in this study. Each population was represented by 3-7 families. Family effect appeared to be the largest for wood hardness and its variance component was 18.4+or-7.6% (P=0.1%). Family x diameter class interaction component was 16.0+or-7.7% (P=1%). Population effect, tested against the family effect as an error term, was not significant and its variance component did not exceed 1%. Additive genetic coefficients of variation for this trait ranged from 0 to 12.7% and only 4 of the analysed 17 populations had estimates exceeding 10%. Genetic correlations with bud burst and growth cessation were negligible positive to weak negative. Though weak, significant estimate indicates better wood trait quality in birch families with longer vegetation period. This type of estimates of wood hardness with height and diameter were 0.23+or-0.06 and 0.71+or-0.08, respectively. Correlation of wood hardness with individual tree selection indexes was 0.15. It can be concluded that even performing birch breeding in the way when wood properties are not examined and used, wood quality in future breeding cycles remains only slightly worse. Also including wood properties in the selection process could lead to a significant improvement of that trait..