VIEW ARTICLE

Techniques

Wet-Sieving Floatation Technique for Isolation of Sclerotia of Sclerotium cepivorum from Muck Soil. R. S. Utkhede, Research associate, Pestology Centre, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6; J. E. Rahe, associate professor, Pestology Centre, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6. Phytopathology 69:295-297. Accepted for publication 31 August 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-295.

A wet-sieving floatation technique that facilitates the rapid isolation of sclerotia of Sclerotium cepivorum from muck soils was developed. Soil samples (20 g) were washed through two stacked sieves (0.595 mm openings over 0.210 mm openings) for at least 5 min, and the residues on the 0.210-mm sieves were transferred to columns containing 2.5 M sucrose solution (1.330 sp gr). After 2 hr, the soil fractions suspended in the upper portions of the columns were collected, washed with water on 0.210-mm sieves, and examined with a dissecting microscope. Sclerotia were removed with forceps, surface sterilized in 0.25% sodium hypochlorite for 2.5 min, washed in distilled water, and cut in half. The two halves were placed on potato-dextrose agar in petri dishes and kept at room temperature (22–25 C) for 2 wk to allow identification of S. cepivorum. Approximately 82% of sclerotia recovered from naturally-infested soils were confirmed to be S. cepivorum. The specific gravity of laboratory-reared sclerotia was greater than that of sclerotia produced in the field.