Long term storage of callus cultures at low temperatures or under mineral oil layer.

Plant tissue cultures from various species were stored at low temperatures or under mineral oil overlay for 4 to 6 months without subcultures. After transfer to normal culture conditions, it was checked, with 3 strains, that growth characteristics and secondary metabolite production were preserved. The storage with a mineral oil overlay (easy to run and economical method) could be a possible alternative to cryogenic or low temperature storage for a large number of strains.