The thalloid liverwort Plagiochasma rupestre supports arbuscular mycorrhiza-like symbiosis in vitro

In the present study, we obtained in vitro dual cultures between the liverwort Plagiochasma rupestre and two arbuscular mycorrhizal (AM) fungi: Glomus intraradices and Glomus clarum. Four agarized culture media were tested for optimal growth of P. rupestre. Also, a description of the symbiotic association is provided. Plagiochasma rupestre gametophytes profusely grew axenically in MM with sucrose, and thalli were successfully subcultured under these growth conditions. Arbuscular mycorrhizal fungal hyphae colonized P. rupestre thalli through rhizoids or by forming appresoria in the ventral thallus cells. Arbuscules, mycelia and structures resembling intrathallic spores or vesicles were developed in the internal parenchymatic cells. The pattern of AM colonization in P. rupestre was very similar to the Paris-type. After 100 days of dual culture, the external mycelia of both AM fungal strains formed thousands of small viable spores, suggesting that P. rupestre in vitro culture could be a valuable tool for studying the biology of both symbiotic partners and conserving AM fungi in in vitro germplasm collections.