Germination, emergence and pyrrolizidine-contents of common groundsel (<i>Senecio vulgaris</i>)

Abstract

The uptake of food contaminated with common groundsel (Senecio vulgaris) is a considerable health risk because of the occurrence of pyrrolizidine alkaloids (PA) in parts of the plant. Agronomical approaches are needed to minimize potential contamination with S. vulgaris. Different temperatures, light conditions and seed pre-treatments were tested during the germination of S. vulgaris to identify the optimum environment for germination. In addition, four sets of S. vulgaris were sown in a field trial at the research station Kleinhoheneim/South West Germany in 2016 to determine the PA pattern and any shift in PA contents in during the year in flowers, leaves and stems. Germination rates were highest (84-87%) when seeds germinated in light without pre-treatment, and a little lower in darkness, at any of the three trial temperatures of 5 °C, 10 °C und 20 °C. Pre-treatment with frost, particularly in combination with cool germination temperatures, lead to significantly higher numbers of intact, ungerminated seeds (75%) compared to the control (20%) or a drought stress pre-treatment (8%). Flowers of S. vulgaris contained up to mg total PA/kg in the air dried plant material (Σ of retrorsine, senecionine, seneciphylline, senecivernine and their corresponding N-oxides) and thus the contents were significantly higher than those in stems or leaves. The PA content in leaves increased significantly during the season. As flowers seem to be the main source of PA, their removal or avoidance in harvested crops is most desired. For avoidance of seed production before winter (with risk of seed persistence due to cold temperatures), herbs and medical plants or lettuce contaminated with S. vulgaris should not be harvested in late summer or autumn. This approach would additionally avoid contamination with S vulgaris with increased PA contents in the harvested product at the end of the season.