Anthracnose is a major production constraint for st. john’s wort (Hypericum perforatum L.) caused by the fungus Colletotrichum gloeosporioides (Penz.). A greenhouse screening method based on mortality was developed to eliminate accessions susceptible to anthracnose in the early stage of breeding for resistant cultivars. The mortality of 22 accessions of st. john’s wort artificially inoculated with a strain of C. gloeosporioides was highly correlated between three greenhouse experiments (r = 0.799 to 0.923), even when done at two different places. The response of the greenhouse screening was equally highly correlated to the mortality in the field tested at two sites naturally infested with C. gloeosporioides (r = 0.700 to 0.865) but less well correlated with the mortality at a third field site (r = 0.495 to 0.672). Yield of st. john’s wort was highly correlated with mortality (r = –0.747 to –0.846) at all three field sites, but a significant interaction between accession and site was observed. Therefore, an improvement of anthracnose resistance of st. john’s wort should be based on a greenhouse screening of seedlings followed by multiple-site field testing of adult plants.
Vincent V. Michel, Nicole Debrunner and Xavier Simonnet
Valtcho D. Zheljazkov, Tess Astatkie, Thomas Horgan, Vicki Schlegel and Xavier Simonnet
Sweet sagewort, also known as sweet wormwood (Artemisia annua L.), contains essential oil and other natural products. The objective of this study was to evaluate the effect of eight different distillation times (DTs; 1.25 minutes, 2.5 minutes, 5 minutes, 10 minutes, 20 minutes, 40 minutes, 80 minutes, and 160 minutes) on A. annua essential oil and its antioxidant capacity. Highest essential oil yield was achieved at 160-minute DT. The concentration of camphor (8.7% to 50% in the oil) was highest at the shorter DT and reached a minimum at 160-minute DT. The concentration of borneol showed a similar trend as the concentration of camphor. The concentrations of some constituents in the oil were highest at 2.5-minute DT (alpha-pinene and camphene), at 10 minutes (paracymene), at 20 minutes (beta-chamigrene and gamma-himachalene), at 80 minutes [transmuurola-4(15),5-diene and spathulenol], at 80- to 160-minute DT (caryophylene oxide and cis-cadin-4-en-ol), or at 160-minute DT (beta-caryophyllene, transbeta-farnesene, and germacrene-D). The yield of individual constituents reached maximum at 20- to 160-minute DT (camphor) at 80- to 160-minute DT [paracymene, borneol, transmuurola-4(15),5-diene, and spathulenol], or at 160-minute DT (for the rest of the oil constituents). DT can be used to attain A. annua essential oil with differential and possibly targeted specific chemical profile. The highest antioxidant capacity of the oil was obtained at 20-minute DT and the lowest from the oil in the 5-minute DT. This study suggests that literature reports on essential oil content and composition of A. annua could be compared only if the essential oil was extracted at similar DTs. Therefore, DT must be reported when reporting data on essential oil content and composition of A. annua.