An ultrastructural study of 'phialospore' formation in Fusarium culmorum grown in continuous culture

Abstract

The macroconidia of Fusarium culmorum can be produced in a semisynchronous way in continuous culture by manipulating the medium pH. Ultrastructure studies of conidiogenesis have shown that the macroconidia are not conventional phialospores, as has long been believed. The first and subsequent conidia are delimited by the fusion of vesicles in the peripheral cytoplasm in the apex of the conidiophore. The conidium wall, including the basal delimiting septum, is formed endogenously. At a late stage of development the expanding conidium ruptures the conidiophore wall and is released by an abscissional splitting of the basal septum. Internal septation of the conidium normally occurs after its release.