The V10 deteriorated variant of Aspergillus nidulans has hyphae, metulae, phialides and conidia with abnormal nuclear distributions. The alterations observed were: increase in the number of nuclei in hyphae, metulae and phialides, presence of anucleate, uninucleate and multinucleate conidia, abnormal vegetative growth and defective conidiation. When 0.5 M NaCl was added to the medium, an increase in the number of conidia was observed but their morphology and number of nuclei were not modified. The gene responsible for these alterations was named anuA1. The anuA1 gene is located on linkage group VII and is possibly involved in nuclear migration to hyphae, metulae, phialides and conidia. z 1998 Federation of European Microbiological Societies