Germination of macroconidia and growth of <i>Sporidesmium sclerotivorum</i> in vitro

Abstract

Macroconidia of Sporidesmium sclerotivorum, a mycoparasite of Scleroninia spp., were induced to germinate by aqueous and ethanolic extracts of sclerotia of sclerotinia minor. Paper chromatography of sclerotial extracts indicated the presence of several amino acids and carbohydrates, chiefly glucose. Glucose was identified as the principal germination stimulant in ethanolic extracts. Glucose, fructose, mannose, cellobiose, sucrose, maltose, trehalose, soluble starch, and glycerol at 0.1% (w/v) stimulated macroconidia to germinate in 3-6 days at 25 degrees C. Crude sclerotial extracts, and glucose combined with inorganic and organic nitrogen sources, supported germination of greater numbers of macroconidia than glucose alone. Yeast extract, Casamino acids, peptone, and several carbon substrates alone did not support germination. Macroconidia germinated well (greater than 30%) over the range of pH 3-7; maximum germination (greater than 80%) occurred at pH 5.0-5.5. Mycelial growth in a glucose - Casamino acids - mineral salts medium was also greatest in the range of pH 5.0-5.5, but growth fell off sharply below pH 4.5 and above pH 6.0. The fungus grew slowly on several complex agar media adjusted to pH 5.5.