Potato Tuber Bruising: Some Are More Hurt Than Others

The expression of complex molecular networks upon changing environments shapes plant performance. The multitude of genes that underlie quantitative traits remains sparsely investigated but needs to be addressed. Information on the functional contribution of single genes or networks to natural phenotypic variation allows a deeper understanding of complex traits and significantly empowers plant breeding. Enzymatic discoloration of potato tuber tissue initiated by mechanical impact (bruising) is a complex trait of the cultivated potato that is crucial for crop quality. In order to identify and validate candidate genes contributing to natural variation of tuber bruising in a panel of Middle-European elite germplasm we conducted a combined omics approach. Association mapping led to the identification of marker-phenotype associations at candidate loci. A comparative proteome survey detected proteins differentially expressed between genotypes with low and high bruising susceptibility. Identification of the proteins revealed novel candidate genes for tuber bruising. Further biochemical and molecular analysis of these candidates provides answers to the questions, “why and how” these genes contribute to bruising and what impact allelic variation has. In this respect, we identified a putative class III lipase as novel candidate, contributing to the bruising. In addition, we demonstrated that allelic diversity of polyphenol oxidases explains part of the variation of tuber bruising and is accompanied by functional diffrences. The combination of association genetics and omics procedures presents a conceptual design to investigate complex plant traits at the molecular level and bridges the gap between basic research and plant breeding by developing molecular diagnostic tools.