Leaf shape in Populus tremula is a complex, omnigenic trait.

Leaf shape is a defining feature of how we recognise and classify plant species. Although there is extensive variation in leaf shape within many species, few studies have disentangled the underlying genetic architecture. We characterised the genetic architecture of leaf shape variation in Eurasian aspen (Populus tremula L.) by performing a genome wide association studies (GWAS) for physiognomy traits. To ascertain the roles of identified GWAS candidate genes within the leaf development transcriptional program, we performed gene co-expression network analyses from a developmental series, which is publicly available within the PlantGenIE resource. We additionally used gene expression measurements across the population to analyse GWAS candidate genes in the context of a population-wide co-expression network and to identify genes that were differentially expressed between groups of individuals with contrasting leaf shapes. These data were integrated with expression GWAS (eQTL) results to...