Viability of Hirsutella spp. strains preserved in mineral oil

Background: culture collections are responsible of the search of alternative methods to preserve fungal species that sensitive to specific techniques due to its characteristics such as the vacuolar size and conidia, susceptibility to desiccation or low temperatures, spore production and slow growth. Objective: to recover 18 isolates of Hirsutella citriformis and two of Hirsutella thompsonii preserved in mineral oil (MO), to assess their viability and suggest this method as alternative for its conservation, in laboratories that do not have the resources for preserve at -70 and -196 °C. Methods: isolates were preserved in MO and recovered in Sabouraud Dextrose Agar (SDA) with 1% yeast extract (SDAY) after six years of preservation, and their viability, morphology and purity were assessed. Results and conclusions: 19 strains of Hirsutella spp. were viable (95%), except for CHE-CNRCB 333. The CHE-CNRCB 345 strain showed differences in its growth, with respect to the initial characteristics observed for H. citriformis. In SDAY H. citriformis produced the characteristic synemas of the species. MO can be used as a preservation alternative for Hirsutella spp. allowing their preservation, compared to sterile water and lyophilization where their viability is reduced.