Effective strategies for isolating DNA from members of Asteraceae with high concentrations of secondary metabolites

The Asteraceae are the largest plant family but among the least studied at the genome level. Our work investigated practical methods to reduce the influence of secondary metabolites - specifically, phenolic compounds - on the extraction of DNA from Silphium spp. This genus is in the Heliantheae tribe of Asteraceae that also includes sunflower (Helianthus annuus). Three methods were attempted in Silphium, with varying condition and age of the leaf sample. A modified cetyl trimethylammonium bromide (CTAB) method on young leaves resulted in the best DNA yield, with sufficient sample purity. No perceptible difference was observed between fresh and lyophilized samples for any extraction method or leaf age. These results provide an excellent basis for DNA extraction of difficult plant samples.