Submitted to: Canadian Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 2001
Publication Date: October 11, 2002
Citation: LOPEZ LASTRA, C.C., HAJEK, A.E., HUMBER, R.A. COMPARING METHODS OF PRESERVATION FOR CULTURES OF ENTOMOPATHOGENIC FUNGI. CANADIAN JOURNAL OF BOTANY. 2002.
Interpretive Summary: There are many possible techniques for the long-term storage of living cultures of fungi, with considerable variations in the overall cost and effectiveness of these various methods for any particular fungus. A broad range of fungal pathogens of insects were tested for their ability to be preserved by storage in deionized water, under mineral oil, on silica gel, or frozen at -20C or -80C. The study included conidial fungi with simple nutritional requirements and several zygomycete and oomycete fungi with very fastidious host and nutritional requirements. The results confirmed that fungi with the least fastidious growth requirements tolerated the greatest range of storage techniques; those with fastidious requirements tolerated fewer of those methods or were killed by all storage regimes tested. This second of two papers comparing methods for the long-term preservation of fungal entomopathogens provides important guidelines for selecting a suitable preservation technique to use for any particular type of fungal entomopathogen. It is unfortunate that the results of this study confirm earlier assertions that the most nutritionally and/or ecologically fastidious a fungal pathogens are often (but not always!) more technically difficult and more expensive to store in a viable condition than fungi with wide host ranges and very nonspecific nutritional requirements.
Nine species of entomopathogenic fungi were tested for viability after they had been stored with deionized water, mineral oil, or silica gel or frozen at -20 or -80C. Species tested included members of Hyphomycetes, Entomophthorales, Trichomycetes and Oomycetes. The fungal cultures were maintained up to 1.5 years and were checked at 3, 6, 12 and 18 months. For rall species evaluated, PAECILOMYCES FUMOSOROSEUS demonstrated the best results, surviving through 18 months when stored with water or mineral oil and when frozen at -80C. For the majority of other fungal species tested except the trichomycete and oomycete, freezing at -80C was the best storage method and storage with silica gel was the worst. For the oomycete LEPTOLEGNIA CHAPMANII and the trichomycete SMITTIUM CULISETAE, infectivity against AEDES AEGYPTI larvae was evaluated after 18 months as well as culture viability. The simplest and most inexpensive methods using water and mineral oil were the only successful methods for maintaining viability and infectivity of these fungi.