Pyrethrins Profiles and Contents in Seedlings, in Vitro Cultures, and Acclimatized Plants of Tanacetum cinerariifolium Clones (Asteraceae)

Abstract

Tanacetum cinerariifolium (Trevir.) Sch. Bip., Asteraceae, known as pyrethrum, is a perennial herb endemic to the eastern Adriatic coast. It is cultivated worldwide for its valuable secondary metabolites: pyrethrins, which are natural insecticides. Pyrethrins are monoterpene esters of chrysanthemum acid (Pyrethrin-I, Cinerin-I, Jasmolin-I) or pyrethric acid (Pyrethrin-II, Cinerin-II, Jasmolin-II) with lethal or knock-down insecticidal properties, respectively. The market demand of pyrethrin-based products is increasing due to the organic farming requirements. In the present study the content of pyrethrins was determined by GC/MS in n-hexane extracts of shoots of several in vitro clones and in flower heads of outdoor acclimatized plants from the same clones during primary and secondary blooming, as well as in seedlings grown on different soil types. Statistical analyses were done by One-way ANOVA Post Hoc LSD analysis. All pyrethrins were detected in all samples, including a Pyrethrin-I isomer but they differed in content and proportion. As expected, pyrethrins in in vitro shoots and in seedlings were in small amounts. However, in the flower heads of the acclimatized plants, pyrethrin content was comparable to that of the native Dalmatian populations. The main component in all samples was Pyrethrin-I, possessing the strongest insecticidal activity, with the highest content in the flower heads of the primary flowering: 4.87 mg/g with a CV of 24.9%. Statistical differences were noted between clones for Pyrethrin-II and the Pyrethrin-I isomer in June samples, and Pyrethrin-I in September samples (p < 0.05). A wide range of variation was also found in seedlings due to different soil types. Growing conditions should be optimized in terms of sunlight and watering, and further research on pyrethrin content should be carried out in several consecutive years.