VIEW ARTICLE

Techniques

Technique for Long-Term Preservation of Phytopathogenic Fungi in Liquid Nitrogen. H. Dahmen, Agricultural Division, Ciba-Geigy Ltd., Basel, Switzerland; Th. Staub(2), and F. J. Schwinn(3). (2)(3)Agricultural Division, Ciba-Geigy Ltd., Basel, Switzerland. Phytopathology 73:241-246. Accepted for publication 29 June 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-241.

Survival, pathogenicity, and sporulation of 31 phytopathogenic fungi (including species from the Myxomycetes, Oomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes) were tested after storage in liquid nitrogen for up to 9 yr. The protective solutions used and rates of freezing and thawing were crucial for successful long-term preservation. Some fungi survived as well in water as in a protective solution. Skim milk-glycerol (8.5% + 10%) and DMSO (15%) were good cryoprotectants for all propagules tested except urediospores of rust fungi, which required dry storage. The samples were frozen either rapidly by direct immersion of the vials in liquid nitrogen or slowly (decreasing 1 C/min to - 40 C) followed by transfer into liquid nitrogen. The samples were thawed either in air at room temperature or in water at 20 or 40 C. For successful recovery, all Oomycetes and Colletotrichum lagenarium required slow freezing. The recovery of all other fungi was equally good after rapid or slow freezing. The rust fungi required thawing at 40 C. All other fungi survived both quick or slow thawing. All but one of the 31 fungal species studied could be preserved for up to 9 yr. We failed to preserve Erysiphe graminis, but we could preserve other powdery mildew fungi such as Podosphaera leucotricha and Erysiphe cichoracearum. This study demonstrates that with suitable protective solutions and proper handling the viability and pathogenicity of a wide range of fungi can be preserved in liquid nitrogen for long periods of time.