We determined steady-state (basal) endogenous levels of three plant hormones (abscisic acid, cytokinins and indole-3-acetic acid) in a collection of thirty different ecotypes of Arabidopsis that represent a broad genetic variability within this species. Hormone contents were analysed separately in plant shoots and roots after 21 days of cultivation on agar plates in a climate-controlled chamber. Using advanced statistical and machine learning methods, we tested if basal hormonal levels can be considered a unique ecotype-specific classifier. We also explored possible relationships between hormone levels and the prevalent environmental conditions in the site of origin for each ecotype. We found significant variations in basal hormonal levels and their ratios in both root and shoot among the ecotypes. We showed the prominent position of cytokinins (CK) among the other hormones. We found the content of CK and CK metabolites to be a reliable ecotype-specific identifier. Correlation with the mean temperature at the site of origin and the large variation in basal hormonal levels suggest that the high variability may potentially be in response to environmental factors. This study provides a starting point for ecotype-specific genetic maps of the CK metabolic and signalling network to explore its contribution to the adaptation of plants to local environmental conditions.

Department of Experimental Biology Faculty of Science Masaryk University Kamenice 5 Brno 62500 Czech Republic

Faculty of Science Palacký University and Laboratory of Growth Regulators Institute of Experimental Botany The Czech Academy of Sciences Šlechtitelů 27 Olomouc 78371 Czech Republic

Functional Genomics and Proteomics of Plants CEITEC MU Central European Institute of Technology Kamenice 5 Brno 62500 Czech Republic

Plant Sciences Core Facility CEITEC MU Central European Institute of Technology Masaryk University Kamenice 5 Brno 62500 Czech Republic

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