Multiplication of peat moss (Sphagnum L.) species for climate action.

Mosses from the genus Sphagnum have experienced 350 million years of separate evolution, resulting in distinctive features, such as unlimited apical growth potential, unknown from other mosses. They are ecosystem engineers and the main components of peatlands. Although peatlands cover only a small part of Earth's landmass, they store more carbon than all living matter combined. Peat mining and agriculture result in degraded peatlands, and thus have a dramatic negative impact on our climate. Sphagnum farming is a promising approach to combat climate change. Here, we review the state of the art with a focus on the establishment of a peat moss collection and their growth in vitro, especially in photobioreactors. Axenic, monoclonal Sphagnum strains have been established from spore capsules that have been collected from different peatlands across Europe. Analyses with flow cytometry have revealed haploid as well as diploid accessions. Optimization of the media composition for several species have resulted in an up to 50-fold biomass increase in a photobioreactor process. Future work should employ transcriptomics for a further optimization of biomass gain. Moreover, the importance of the Sphagnum microbiome should be considered for transplantation of the axenic, clonal moss material to open fields.