Implications of Breeding for Growth on Drought Tolerance in Scots Pine ( L.)-Insights From Metabolomics and High-Throughput Plant Architecture Analysis.

Drought has been identified as one of the important environmental factors in the context of climate change due to its interaction with other biotic and abiotic stresses. However, only a few studies have reported the effect of breeding on forest adaptability to climate change. Using a common garden experiment with seedlings from families of Scots pine ( L.) from northern Sweden, we have found differences in drought tolerance between seedlings from breeding stands and those from natural forests. We performed a genetic analysis including high-throughput image-based phenotyping of seedling canopy and root traits and conducted metabolomic and hormone analyses with the aerial parts of the seedlings. Our results indicate that root architecture traits associated with drought tolerance exhibit moderate to high heritability. Analyses of seedling architecture reveal that families from breeding stands have higher drought resistance but lower genetic variation than the ones from natural forests, especially in the case of canopy traits. Metabolomic and hormone analyses of the aerial parts of the seedlings also support that the breeding stands may have a higher capacity to withstand or deal with drought conditions as compared to the natural forests. For example, increase in abscisic acid along with increase in tryptophan and auxin conjugates in the breeding stands compared to the natural forests under drought conditions may contribute to alleviation of drought response in the breeding stands. The methodology employed to evaluate drought tolerance and plant architecture in this study might be useful for future research and forest management focused on climate change adaptability.