Regeneration of northern conifer forests is commonly performed by reforestation with genetically improved materials obtained from long-term breeding programs focused on productivity and timber quality. Sanitary threats can, however, compromise the realization of the expected genetic gain. Including pest resistance traits in the breeding programs may contribute to a sustainable protection. Here we quantified the variation in different components of resistance of Norway spruce to its main pest, the pine weevil Hylobius abietis. We followed insect damage in two large progeny trials (52 open-pollinated families with 100–200 individuals per family and trial) naturally infested by the pine weevil. Pine weevils damaged between 17 and 48% of the planted seedlings depending on the trial and year, and mortality due to weevil damage was up to 11.4%. The results indicate significant genetic variation in resistance to the pine weevil, and importantly, the variation was highly consistent across trials irrespective of contrasting incidence levels. Individual heritability estimates for the different components of seedling resistance were consistently low, but family heritabilities were moderate (0.53 to 0.81). While forward selections and breeding for higher resistance seem not feasible, backwards selections of the best parent trees emerge as a putative alternative to reduce weevil damage. A positive genetic correlation between early growth potential and probability of being attacked by the weevil was also observed, but the relationship was weak and appeared only in one of the trials. Overall, results presented here open the door to a new attractive way for reducing damage caused by this harmful pest., This research was part of the Parasite Resistant Tree Project funded by the Swedish Foundation for Strategic Research,
Grant RBb08-0003, to GN and SJ. LS and RZ were supported by the Grant FUTURPIN AGL2015-68274-C03-02R funded by MINECO/FEDER and by the GAIN-Xunta de Galicia Grant IN607A2016/013., Peer reviewed, Peer Reviewed

11 Pág., Quantifying intraspecific genetic variation and phenotypic plasticity of traits involved in drought tolerance is essential to forecast forest tree vulnerability to climate change. Tree ring analysis was applied to retrospectively assess the resistance, recovery and resilience of a Mediterranean pine in the face of extreme climate episodes. We combined a dendrochronological approach with the analysis of common-garden tests to disentangle genetic, environment and genetic-by-environment effects in growth responses of 10 P. pinaster populations to two extreme climatic events. Trees were 43 years old and had experienced two intense droughts, in 1995 and 2005. Drought events caused drastic reductions in secondary growth, but trees showed high capacity to recover pre-drought growth rates. The differences in the characteristics of the two drought events and the environmental distance between sites strongly modulated maritime pine responses to extreme droughts. However, a common among-population signal across sites and events was detected in the drought response strategy. Among-population variation in response to extreme droughts was evident for the resistance and recovery components, two strategies that appeared to trade-off between each other. Populations from Atlantic climates showed higher resistance but lower recovery capacity, whereas Mediterranean origins prioritised recovery over resistance. Mediterranean populations showed a more conservative strategy that indicated an adaptive advantage under water stress, reflected in greater long-term survival. The abovementioned relationships were clear in the site where the impact of the drought events was strongest, but not in the more favourable site. Differences in relationships between sites reflect that strategies of populations to cope with drought are strongly context dependent. Based on these results, we infer that future extreme droughts will differentially affect P. pinaster populations across the natural range of the species. Immediate effects will be more evident in Mediterranean areas but, in the long term, population persistence in the face of climate change will be more compromised for Atlantic origins. Because local environmental conditions can considerably modulate responses to extreme events, special attention is required to define appropriate management practices to mitigate the impact of future droughts., This research was funded by Spanish Government (MINECO/FEDER) grants FENOPIN (AGL2012-40151-C03-01) and FUTURPIN (AGL2015-68274-C03-02-R) and Xunta de Galicia-GAIN grant (IN607A2016/013). Language edition was funded by the European Regional Development Fund (ERDF, 'A way to achieve Europe') and the Government of Extremadura (Ref. GR18193). M. Vivas was supported by a “Juan de la Cierva program” funded by the Ministry of Economy, Industry and Competitiveness of the Spanish Government. The authors thank José Climent (INIA-CIFOR, Madrid, Spain) for providing basic information and data from the provenance trials, Jane McGrath for English edition of the manuscript, and Carla Vázquez for her help in climate data processing and figure editing. The staff of Cabañeros National Park is acknowledged for their logistic assistance in field work. César Cendán (MBG-CSIC) and David Castañe (USC) also helped in field work., Peer reviewed