Oxalate production by virulent but not by hypovirulent strains of Endothia parasitica

Abstract

Three virulent strains of Endothia parasitica when grown on potato dextrose agar containing methionine and biotin (PDAmb) or minimal media containing glucose supplemented with either glycolate or glyoxylate produced 10–12, 50–60 and 20–40 mg oxalate g −1 dry weight of fungus respectively. Oxalate accumulation was detected the fourth day after inoculation when the strains were grown on PDAmb or the glycolate medium but not until day 7 on the glyoxylate medium. In the early stages of growth (up to 0·1 g dry weight per colony) the total amount of oxalate excreted into the medium was proportional to the dry weight of the fungus but there was little or no correlation at later stages of growth. Oxalate was detected at the edge of the fungal colony, which is important if oxalate is to play a role in pathogenicity. Under identical conditions three hypovirulent strains, derived from the virulent ones by the introduction of cytoplasmic determinants for hypovirulence, produced no detectable oxalate.