Electrophoretic karyotype and gene mapping of the vascular wilt fungus Verticillium dahliae

The karyotype profile of Verticillium dahliae was resolved by pulse-field gel electrophoresis. It revealed 6 chromosomal bands that corresponded to 7 chromosomes as shown by RFLP analysis using as probe the telomeric consensus sequence (AACCCT)5. The number of chromosomes was further verified by the sensitivity of the hybridization signals to Bal31 digestion and the exclusion of interfering mitochondrial DNA signals. The corresponding sizes of the seven separated chromosomes were 6.7, 5.6, 4.1, 3.4, 3.1, 3.1 and 2.4 Mb, raising the total genomic size of the fungus to approximately 28.4 Mb. Twenty five homologous V. dahliae genes obtained either from randomly sequenced clones or PCR amplification were used as hybridization probes and were located onto the seven chromosomes.