Significance of genetic and environmental aspects in the field cultivation of Hypericum perforatum.

Agronomical and biochemical parameters of seven Hypericum perforatum (St. John's wort) accessions grown at three experimental sites in Switzerland were followed over a two year period (1995-1996). Significant effects of environmental (= site) and genetic factors (= accession) on flowering dates, plant length, and plant dry matter production (= plant yield) were observed in both years; rankings of sites and accessions with regard to plant yield were similar in both years despite the fact that the first year crop contributed only a minor part to the overall yield of both years together. Maximum dry matter production per year reached 159 dt/ha for the total plant and 54 dt/ha for the flowering segment (i.e. the pharmaceutically relevant, upper segment of the plants comprising the majority of flowers). HPLC analysis of the constituents covered eight secondary metabolites (amentoflavone, biapigenin, hyperforin, hypericin, hyperosid, pseudohypericin, quercetin, rutin). Generally, secondary metabolite contents were significantly lower in the first year of cultivation ranging from 12% (hyperosid) to 83% (hyperforin) of the contents measured in the 1996-crop. Significant genetic effects on the production of all tested secondary metabolites (except biapigenin) were observed in 1996 whereas environmental effects appeared to be less distinct (except for amentoflavone and pseudohypericin). In conclusion, genetic factors strongly affected plant yield as well as secondary metabolite content in H. perforatum cultivation; the availability of genetically superior plant material next to improved agrotechnological methods therefore is supposed to become a key factor for successful future field production.