Genetic variation in resistance to Phytophthora cinnamomi in seedlings of two Turkish Abies species

Genetic variation in resistance to Phytophthora cinnamomi was investigated for two fir species endemic to the Republic of Turkey. Open-pollinated families of seedlings of Trojan fir (Abies equi-trojani) and Turkish fir (Abies bornmuelleriana) were grown from seed in a greenhouse for approximately 15 months, inoculated with rice grains colonized with P. cinnamomi, and subsequent mortality assessed biweekly for 16 weeks. Final seedling mortality was higher in Trojan fir (56.4 %) compared to Turkish fir (32.9 %). Mortality in both species varied by geographic origin, decreasing from west (59.8 %, [inline-graphic not available: see fulltext]) to east (21.4 %, Karabük). As mortality increased following inoculation, both narrow-sense individual-tree \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {h_i^2} \right) $$\end{document} and family mean \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ ( {h_f^2} ) $$\end{document} heritabilities increased, plateauing at 0.62 ± 0.162 and 0.97 ± 0.011 for Trojan fir and 0.50 ± 0.102 and 0.96 ± 0.01 for Turkish fir, respectively. Terminal and lateral branch bud break assessed under greenhouse conditions were also under strong genetic control. For terminal bud break, individual-tree heritabilities for Trojan and Turkish fir were 0.49 ± 0.146 and 0.45 ± 0.099, respectively, while family mean heritabilities were 0.88 ± 0.035 and 0.88 ± 0.027, respectively. The family mean correlation between bud break and final disease mortality was not significant for lateral buds but positive and significant for terminal buds (r = 0.32) suggesting that selection for resistance would either not alter, or slightly reduce, early bud break. These are encouraging results for ongoing tree improvement efforts in North America and Europe to develop planting stock for the Christmas tree industry.