Abstract
Root herbivores can affect plant fitness, and roots often contain the same secondary metabolites that act as defenses in shoots, but the ecology and evolution of root chemical defense have been little investigated. Here, we investigated genetic variance, heritability, and correlations among defensive phenolic compounds in shoot vs. root tissues of common evening primrose, Oenothera biennis. Across 20 genotypes, there were roughly similar concentrations of total phenolics in shoots vs. roots, but the allocation of particular phenolics to shoots vs. roots varied along a continuum of genotype growth rate. Slow-growing genotypes allocated 2-fold more of the potential pro-oxidant oenothein B to shoots than roots, whereas fast-growing genotypes had roughly equivalent above and belowground concentrations. Phenolic concentrations in both roots and shoots were strongly heritable, with mostly positive patterns of genetic covariation. Nonetheless, there was genotype-specific variation in the presence/absence of two major ellagitannins (oenothein A and its precursor oenothein B), indicating two different chemotypes based on alterations in this chemical pathway. Overall, the presence of strong genetic variation in root defenses suggests ample scope for the evolution of these compounds as defenses against root herbivores.
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Acknowledgments
We thank Alex Smith, Marc Johnson, Mike Stastny, Kailen Mooney, Scott McArt, Susan Cook-Patton, Alexis Erwin, Jennifer Thaler, Piia Koskinen, and Marc Lajeunesse for discussions or assisting with field and laboratory work. This work was supported by NSF-DEB 1118783 (A.A.A.).
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Parker, J.D., Salminen, JP. & Agrawal, A.A. Evolutionary Potential of Root Chemical Defense: Genetic Correlations with Shoot Chemistry and Plant Growth. J Chem Ecol 38, 992–995 (2012). https://doi.org/10.1007/s10886-012-0163-1
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DOI: https://doi.org/10.1007/s10886-012-0163-1