Anatomy and histochemistry of stromatal anamorphs in the Sclerotiniaceae

Abstract

As part of comparative studies of stromata in the Sclerotiniaceae, mature sclerotial and substratal stromata produced in vitro by 19 species, and 1 form-species, representing 13 genera and 1 form-genus, were examined using light microscopy and histochemical staining. Sclerotial-stromatal taxa were Sclerotinia sclerotiorum, S. trifoliorum, S. minor. Sclerotium cepivorum, Botrytis cinerea, B. porri, Dumontinia tuberose, Ciborinia erythronii, Myriosclerotinia dennisii, M. borealis, Monilinia fructicola, and Stromatinia gladioli. Substratal-stromatal taxa were Lambertella subrenispora, Lanzia luteovirescens, Rutstroemia sydowiana, Stromatinia gladioli, Ovulinia azaleae, Sclerotinia homoeocarpa, Scleromitrula shiraiana, and Ciboria acerina. Histochemical staining, particularly 0.05% toluidine blue O in benzoate buffer at pH 4.4, was found to be useful in demarcating the zones within stromata: rind, cortex, and medulla. All sclerotia contained extensive reserves of carbohydrates in thick cell walls and copious extracellular matrix, while protein bodies were usually the major cytoplasmic storage reserve. A group of saprophytic, substratal isolates had thin medullary cell walls and less extracellular matrix, and did not store protein but stored large deposits of lipid in cytoplasm. A group of phytopathogenic, substratal-stromatal isolates appeared to be transitional, with anatomical features and extensive cytoplasmic protein body reserves suggesting that they produce indeterminate sclerotial stromata rather than true substratal stromata.