Towards the valorization of the invasive seaweeds Caulerpa cylindracea and Asparagopsis taxiformis in the Mediterranean Sea: applications for in vitro plant regeneration and crop protection

Caulerpa cylindracea and Asparagopsis taxiformis are both invasive seaweeds representing a major threat to indigenous species and the native ecosystems of certain regions of the Mediterranean Sea. This work examines the possibility of adding value to this abundant biomass in the fields of in vitro culture and plant protection. Results showed that using a 10% aqueous extract from C. cylindracea and A. taxiformis to in vitro culture media enhanced the regeneration percentage of apricot hypocotyl slices, as well as the diameter of explants and the number of regenerating buds per explant. The combination of extracts from these two seaweeds with an increasing concentration of conventional plant growth regulators further significantly enhanced most of these parameters. In addition, the data showed that soaking seeds of Nicotiana benthamiana in a 1.5% solution of aqueous extracts of C. cylindracea resulted in seedlings with reduced disease severity, when inoculated with the plum pox virus. These observations demonstrated that it would be possible to transform and perhaps manage the biomass of these invasive algae, which could pave the way to multiple valorizations.