Rapid screening of Medicago truncatula germplasm for mercury tolerance at the seedling stage

- A rapid screening of Medicago truncatula germplasm was performed for Hg tolerance.
- 258 cultivars were tested using seedling root growth as an indicator of tolerance.
- The results of the screening were validated in a hydroponic experiment.
- A factorial analysis of the growth parameters defined tolerance indices.
- The tolerant cultivars identified may be useful in soil phytoremediation strategies.

The development of novel phytoremediation strategies to mitigate mercury contamination, an increasingly important worldwide threat, could be enhanced by identifying Hg-tolerant legume cultivars. A fast method was thus developed to screen a germplasm collection of the model legume Medicago truncatula for Hg tolerance, testing 258 accessions at the seedling stage in a miniaturized hydroponic system and using root growth as an indicator of tolerance. To validate the results of the screening, the Hg-tolerant cultivars identified were analyzed in a referenced hydroponic growth assay. The different growth parameters measured in this assay were then subjected to a factorial analysis (principal component analysis method) in order to establish indices of tolerance, which further supported the rapid method of screening. Accordingly, four Hg-tolerant M. truncatula cultivars were selected that might serve as source material for genetic improvement, as model cultivars to study Hg tolerance in legumes and/or to develop soil phytoremediation approaches.