WILD CHROMOSOMAL VARIANTS IN ASPERGILLUS-NIDULANS

Pulsed-field gel electrophoresis and a chromosome-specific cosmid DNA library were used to determine the karyotypes of wild-type Aspergillus nidulans isolates from around the world. Overall, little structural v ariation was found, with a few major exceptions. One isolate possessed a non-essential B-chromosome of about 1.0 million base pairs (mb). An other isolate had undergone a non-reciprocal translocation of about 1. 6 mb of chromosome VI onto chromosome VIII. Other than these chromosom al differences, these isolates appeared phenotypically normal. To anal yze its effects on meiosis, the translocation isolate was outcrossed w ith another wild-type derivative that had a ''normal'' electrophoretic karyotype. This cross produced a range of phenotypes, including dupli cated progeny that had a ''barren'' phenotype similar to that describe d for Neurospora partial disomics. The duplication was somewhat vegeta tively unstable. This is the first association of sterility with chrom osomal duplication in A. nidulans.