Arginine auxotrophy (Arg(-)) was induced in two Aspergillus niger strains, previously reported as 2-deoxy-D-glucose (2DG) resistant and pectinase overproducing mutants in either solid state fermentation (SSF) or submerged fermentation (SmF). Only one of these two arginine auxotrophs (strain Aw99ARG) was transformed with a plasmid containing the A. nidulands argB gene, indicating that this strain was affected in this particular gene. A diploid (D4) was generated via parasexual recombination between these two Arg- strains and was characterized with regard to 2DG sensitivity and pectinase production. This diploid showed wild type sensitivity to 2DG, suggesting that recessive mutations at two different loci were involved in 2DG resistance in each parent strain. The diploid had also increased pectinase production in SmF (127% higher) when compared to the wild type strain, from which all pectinase overproducing mutants were previously isolated, and 10% over Aw99-iii2 strain, formerly characterized as an overproducing strain in SmF.