The focus of the DyCLE project was on describing and analysing within-population variation in Cd hyperaccumulation of A. halleri. A field trip for plant monitoring was planned every 6 months, for a total of three trips. During the first field trip, leaves and rhizosphere soil from approximately 30 individuals were collected on both sites. Each sampled plant was marked with a plastic strap attached to a plastic label in order to be able to find the same individual again during the one-year monitoring. Plants were photographed, and semi-quantitative classification of herbivory damage and density of competing plants were documented. The collected samples were analysed through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) for their metal content. Based on Cd concentrations in leaves, contrasting genotypes were selected within each of the two populations. Field trips no. 2 and 3 were each delayed by approximately 6 months due to the COVID-19 pandemic. During the second field trip, we sampled the two plants with the highest, two plants with intermediate, and the two plants with the lowest leaf Cd concentrations previously identified (“focus genotypes”).
In the second part of the DyCLE project, we produced vegetative clones from each of the focus genotypes in order to test the elemental defence hypothesis. We also collected approximately 300 kg of natural soil from the Gott field site. After 2 months of pre-cultivation, clones were moved into 1-L pots filled with Gott soil and cultivated for 5 weeks with or without mechanical damage (herbivory simulation). The herbivory simulation was done four times over a 9-day period. At the end of the experiment subsamples of leaves were analysed for metal content by ICP-OES. However, due to the COVID-19 pandemic, these experiments were done with a delay of approximately 8 months, and therefore, leaf glucosinolate concentrations have not been measured yet. In the third part of the project, 5 large clones of each selected genotype grown on Gott soil, were moved from our greenhouse to our outdoor garden site. Plants were left unsupervised and watered as necessary. Plants were monitored each day, and leaves were harvested after a major incident of slug feeding on the leaves. Metal concentrations as quantified by ICP-OES were compared with those of control plants that had been protected from herbivory by a net.
The preliminary results from experiments under controlled conditions support the hypothesis of genotype-herbivory interaction in tuning leaf metal concentrations. Project results dissemination through different communication channels is in preparation. There are currently two manuscripts of review articles in preparation, which will soon be submitted to peer-reviewed journals. An original manuscript containing results from fieldwork and experiments under controlled conditions is also in preparation. Project results were also presented to the scientific community at two international conferences (POPBIO2021 and ICAR 2021). The major objectives of the DyCLE project were presented to researchers and students at the regular meetings of the department and in a dedicated newsletter, YouTube channel, and website. Training in (additional) skills, transferable and complementary skills was attended, as well as the initiation of new collaborations and projects.
