High genetic variation and moderate to high values for genetic parameters of Picea abies resistance to Pissodes strobi

Genetic parameters of Picea abies resistance to the white pine weevil (Pissodes strobi Peck) were estimated from 193 full-sib and 166 half-sib families in six 10-year-old progeny trials. The estimated family and individual heritability values for the cumulative weevil attack rate between ages 6 and 10 (CWA6–10) were high and moderate for both full-sib families (0.61 and 0.28, respectively) and half-sib families (0.85 and 0.40, respectively), indicating strong genetic control for this trait in Norway spruce. The fact that specific combining ability (SCA) variance represents 35 % of the general combining ability (GCA) variance suggests that non-additive (dominant) effects are weak. The strong type B correlations found for CWA6–10 (r^B=0.96\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\widehat{r}}_{\mathrm{B}}=0.96 $$\end{document} for full-sib families and r^B=0.81\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\widehat{r}}_{\mathrm{B}}=0.81 $$\end{document} for half-sib families) indicate that family ranks were stable across sites. For three of the five sites with high attack levels, genetic correlations were not significant between CWA6–10 and tree height at age 5. Moderate positive genetic correlations were detected between CWA6–10 and tree diameter at age 10 (r^A\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\widehat{r}}_{\mathrm{A}} $$\end{document} from 0.29 to 0.60), but specific families showing both high resistance and good diameter growth can be found. These results suggest that the genetic improvement of Norway spruce for resistance to white pine weevil can be achieved successfully without adversely affecting growth.