Studies on the fungitoxicity of captan

The cytological changes in Neurospora crassa conidia following treatment with captan at the ED ₅₀ fungicidal dose have been examined by electron microscopy. With dormant conidia the only observable effect of captan was to produce a characteristic convoluted form of the nuclear membrane. It is suggested that this effect may be due to the reaction of captan with the sulphydryl groups of the nuclear proteins leading to an inhibition of cell division. The cytoplasmic membrane was unaffected by captan, confirming that this fungicide does not destroy cell permeability barriers. After incubation in Fries medium, captan-treated spores showed an almost complete loss of internal fine structure. Similar results were obtained with ‘protoplasts’ of N. crassa which showed disorganization of mitochondrial structure after captan treatment.