Asterionella formosa is a freshwater pennate diatom that forms star-shaped colonies, whose mitochondrial DNA was recently sequenced . This diatom is of interest for genetic studies\u00a0[2,3]\u00a0and for the study of photosynthesis\u00a0[4,5].\u00a0However, extraction of genomic DNA (gDNA) from A. formosa is difficult because of its silica cell-wall and the presence of photosynthetic pigments that contaminate the DNA. Here, we present an optimised protocol for gDNA extraction from A. formosa that overcomes those two problems. We also assessed its efficacity in yielding high-purity gDNA compared to a standard protocol using hexadecyltrimethylammonium bromide (CTAB).References Villain A. et al. (2017) Mitochondr. DNA. 2 (1), 97-98. De Bruin A. et al. (2004) J. Phycol. 40, 823-830. van Den Wyngaert S. et al. (2015) Mol. Ecol. 24, 2955-2972. Boggetto N. et al. (2007) J. Phycol. 43, 1227-1235. Erales J. et al. (2008) J. Phycol. 44, 1455-1464.