Influence of storage method on the viability, mycelial growth and pathogenicity of Sclerotinia sclerotiorum sclerotia

Abstract

The effect of three storage methods on the viability, mycelial growth and pathogenicity of Sclerotinia sclerotiorum (isolate S36) sclerotia was determined with a view towards establishing an optimal method for storing this pathogen during its mass production as a mycoherbicide for controlling the weed Ranunculus acris. Sclerotia were stored at −80°C, 4°C after desiccation, or at room temperature after freeze-drying and their germination, growth and pathogenicity were assessed after 6, 12, 18, 24 and 30 months in these conditions. Germination was maintained at 100% at −80°C and when dry-stored at 4C. In contrast, freeze-dried sclerotia showed a significant reduction in germination and insufficient mycelium was produced at 30 months for growth and pathogenicity assessments. Colony growth from the stored sclerotia was similar for all three storage methods and durations. Pathogenicity, assessed using the leaves of R. acris, was the same for all three storage methods. This study indicates that the sclerotia of S. sclerotiorum may be successfully stored either at −80°Cor at4°C after desiccation for use as a mycoherbicide, but that freeze-drying is not a suitable method.

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