Interlaboratory comparison of methods to quantify microsclerotia of Verticillium dahliae in soil

摘要

Various methods have been employed for directly quantifying Verticillium dahliae in soil (4) but in all of these, soil is plated on a semi-selective medium and colonies are counted after a period of incubation. The methods fall into two categories depending on whether the soil is distributed onto the agar medium dry (dry plating, designated DP) or suspended in water (wet plating, designated, WP). In WP the soil suspension may be sieved prior to plating to remove particles at the size extremes of microsclerotia (<20 #mu#m and >100 #mu#m). Dry plating involves the use of the Andersen sampler (1,3) to distribute the soil particles evenly over the agar medium (2). For both methods, soil is dried prior to analysis to kill conidia and mycelium of V. dahliae, to reduce inoculum of other fungi, and to facilitate grinding and mixing of the soil sample. The aim of this study was to compare the results obtained by several laboratories using their own favoured method of analysis with a range of soils.