ABSTRACT

This study was carried out for the selection of nitrate non-utilizing mutants in Aspergillus flavus. Selection and identification of nitrate non-utilizing (nit) mutants of Aspergillus flavus were evaluated on three chlorate-containing agar media. Three isolates of A. flavus were used. Nit mutants isolated comprised phenotypic classes, equivalent to nirA- mutants of A. flavus. There were significant differences among isolates and media in the number and types of nit mutants isolated. After growing on PDA, mutants are created when placed on PDC. The selection of mutants was done with minimal medium containing nitrate. The Minimal medium contained only nitrate as a nitrogen source. The morphology of nit mutants were more distinctive in this medium than in other media. The nitrate-only medium yielded mainly nit mutants; other media yielded more nirA- mutants, which complement niaD mutants. The use of a nitrate-only medium in conjunction with another medium should optimize the isolation of nit mutants and complementary pairs of mutants.