Biocontrol activity of effusol from the extremophile plant, Juncus maritimus, against the wheat pathogen Zymoseptoria tritici.

Zymoseptoria tritici, responsible for Septoria tritici blotch, is the most important pathogen of wheat. The control of this parasite relies mainly on synthetic fungicides, but their use is increasingly controversial and searching for alternative management strategies is encouraged. In this context, the biocontrol potential of crude methanolic extracts of eight extremophile plant species from Tunisia, including three xerophytes and five halophytes, against Z. tritici was assessed. Only the extract of Juncus maritimus rhizomes showed significant in vitro antifungal activity. In extremophile plants, the production of secondary metabolites is often influenced by abiotic conditions. Thus, we collected several samples of J. maritimus rhizomes at different vegetative stages, at different periods, and from different substrates to compare their antifungal activities. Our results suggest that the plant environment, especially the substrate of the soil, should be taken into account to identify great sources of natural antifungal products. From the most active sample, a 9,10-dehydrophenanthrene derivative, effusol, absent from other J. maritimus rhizomes extracts, was purified. This product showed a strong antifungal activity against the pathogen, with a minimal inhibitory concentration of 19 μg mL-1 and an half-maximal inhibitory concentration of 9.98 μg mL-1. This phenanthrene derivative could be a promising biocontrol molecule against Z. tritici.