DNA-based identification of Calendula officinalis (Asteraceae)1

Ap Applicati tions ons in in Pl Plant t Scien Sciences ces Calendula L. (marigold) is the type genus of the small tribe Calenduleae (Asteraceae). While all other genera of the Calen-duleae are native to southern Africa, Calendula is distributed in the Northern Hemisphere. Calendula species occur mainly in the Mediterranean area, from Morocco and Spain to Iran, southward to the Hoggar Mountains (Algeria) and Yemen (Norlindh, 1946), and northward to Germany and Poland. The center of distribution is northwestern Africa; eight species are listed in the Flora of northern Morocco (Valdés et al., 2002). The genus Calendula consists of 12 annual or perennial species, which are regarded as taxonomically complicated due to hybridiza-tions (Norlindh, 1977 ; Heyn and Joel, 1983). Within the genus, C. offi cinalis L. (common marigold) is of special importance due to its use as an economic crop. Calendula offi cinalis fl ow-ers are used for pharmaceutical purposes (EDQM, 2014), in skin care products because of their anti-infl ammatory activity (Talhouk et al., 2007), and as feed additives to improve the color of food because of their orange color (carotenoids) (Mukherjee et al., 2011). Florets of orange cultivars are also used as an adul-terant of the expensive spice saffron (Marieschi et al., 2012). The fruits of C. offi cinalis are rich in fatty oil that has, because of its unusual composition, numerous technical applications (Zanetti et al., 2013). Common marigold is also an important ornamental plant with many cultivars. The fl ower heads are up to 5 cm in diameter, which is relatively large compared to other species of the genus. The fl ower heads vary from pastel yellow to deep orange, and several cultivars are double fl owered. At present, the identifi cation of C. offi cinalis is often performed by (high-performance) thin-layer chromatography (TLC) or by using morphological characters (EDQM, 2014 ; AHPA, 2015). To the best of our knowledge, DNA-based methods do not yet exist. It can be assumed that TLC is not able to distinguish all Calendula species, and that processed plant material (e.g., fi ne-cut or ground fl owers) cannot be identifi ed to species level by morphology. Therefore, a DNA-based method to identify this species has the potential to complement existing methods in quality control. High-resolution melting curve analysis (HRM) is based on the melting behavior of relatively short, double-stranded DNA fragments and is a fast and reliable post-PCR method …