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Abstract

Plant hormones are primary regulators of plant growth and development. The phytohormone auxin is related to almost all of these growth-related processes. In this thesis, I studied naturally occurring variation of growth-related traits in young Arabidopsis thaliana seedlings upon auxin treatments. In the context of adaptive selection, different quantitative genetic approaches were used and combined with the results of a population genetic study to identify genes, which might contribute to the observed phenotypic variation. The population genetic analysis included a total of 151 genes known to regulate auxin biosynthesis, metabolism, transport and signaling. To analyze auxin response traits on a functional level, quantitative genetic analyses like quantitative trait loci (QTL) mapping and genome-wide association (GWA) mapping were conducted. In general, the genetic architecture regulating the phenotypic variation in the investigated populations seems to be very complex and dominated by small effect loci. Taken together, while the complex architecture of the auxin network probably prevented the identification of large effect loci, some promising candidate genes and genomic regions were identified which require future functional validation.