Application of metabolomics to genotype and phenotype discrimination of birch trees grown in a long-term open-field experiment
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The principal objectives of the study were to develop metabolomics tool and to test its efficiency for discrimination and biochemical pattern recognition of genotypes and phenotypes of silver birch trees (Betula pendula Roth). In the experiment were used two birch genotypes (GT 2 and GT 5) that have been grown over seven years on the two open fields A and B. The metabolomics tool was applied also to study biochemical responses of the GT 2 to elevated (1.5 × ambient) concentration of ozone as an environmental stress factor. These trees were treated with ozone over seven years using an open-air exposure system. The developed metabolomics tool was based on the analyses of lipophilic and polar compounds of birch leaves with GC-MS and HPLC-DAD (polar phenolics only). The metabolome database included 331 chemical traits and was analyzed with descriptive and multivariate statistics. Application of cluster and principle component analyses clearly discriminated genetically different birch trees. In addition, the genotype clusters were further divided into two subclusters corresponding to trees from field A and field B. Formation of these phenotypes was due to the differences in some environmental conditions between the field A and field B. Biochemical discrimination between phenotypes of control and ozone-treated birch trees of GT 2 was found also. However, distances between these phenotypes, as well as between phenotypes of control trees from the field A and field B were found to be considerably smaller than between birch genotypes. Metabolites with the largest contribution to birch genotype/phenotype discrimination were determined and some were identified.
KeywordsMetabolomics GC-MS HPLC-DAD Silver birch Biochemical response Environmental stress Ozone
This work was funded by the Academy of Finland, projects 201073 (VO) and 51758 (EO). We thank Timo Oksanen for ozone fumigations.
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