CLONING AND ASSIGNMENT OF LINKAGE GROUP LOCI TO A KARYOTYPIC MAP OF THE FILAMENTOUS FUNGUS ASPERGILLUS-FLAVUS

The purpose of this study was to develop a karyotypic map of A. flavus and assign parasexually defined linkage groups to chromosomes. Seven A. flavus chromosomal bands, ranging in size from 2.3 to 7.0 megabases were separated by clamped homogeneous electric field gel electrophore sis. Polyethylene glycol-mediated transformation of A. flavus with a w ildtype cosmid genomic library was used to complement seven strains ha ving auxotrophic mutations in genes mapped to six of the eight linkage groups. DNA from cosmids complementing each of these seven mapped aux otrophic genes was used to make linkage group-specific probes. Hybridi zation of these probes to chromosomal separations allowed us to assign six linkage groups (I, II, IV, VI, VII, VIII) to five chromosomal ban ds. In addition, five previously cloned but unmapped genes were locate d on this karyotypic map and thus assigned to their corresponding link age groups, i.e., benA, rDNA, pyrG, aflR and adh1 to groups I, II, II, VII, and IV or VIII, respectively. This karyotypic map will provide l inkage group mapping of most cloned genes without parasexual analysis.