The present invention relates to a method for the identification of antifungal substrates, in particular substrates which are capable of combating filamentous fungi by disturbing cell wall biogenesis. A nucleotide sequence encoding .alpha.-1,3-glucan synthase including its promoter sequences is provided, obtainable from Aspergillus niger, which can be used to develop a reporter system for the identification of a new antifungal compounds in filamentous fungi. The invention relates also to antifungal substrates so obtained and to methods for applying such substrates, in particular in the treatment or prophylaxis of human and animal fungal infections, plant diseases caused by fungi or in the preservation of food against deterioration by fungal growth.