Protoplasts isolated from sporidia of Ustilago maydis were stored by freezing for more than two months. After thawing, the survival of protoplasts was estimated using the vital stain phenosafranine. In a buffered and osmotically stabilized medium containing polyvinyl-pyrrolidone (15% (w/v), PVP) as cryoprotectant, nearly 100% of the protoplasts remained viable, if cooled slowly to − 80 °C. Cell-wall regeneration and reversion frequency of the protoplasts after storage was investigated to further prove cell viability. No significant difference was detected comparing freshly isolated and stored protoplasts. © 1992, British Mycological Society. All rights reserved.
Eidtmann, A., & Schauz, K. (1992). Cryopreservation of protoplasts from sporidia of Ustilago maydis. Mycological Research, 96(4), 318–320. https://doi.org/10.1016/S0953-7562(09)80945-3