MINICHROMOSOMES IN FUSARIUM SPOROTRICHIOIDES ARE MOSAICS OF DISPERSEDREPEATS AND UNIQUE SEQUENCES

Variations in trichothecene patterns of 26 Fusarium sporotrichioides i solates from different plant and geographic origins showed no correlat ion with electrophoretic karyotype polymorphisms. When intact chromoso mes were examined, interisolate karyotype differences were observed on ly in the mini-chromosome range. Further polymorphisms were revealed i n Notl-digested samples. By summing the Notl fragments the average gen ome size of F. sporotrichioides was estimated to be 20.4 Mb. Mini-chro mosonres shared common sequences with the larger ones; however, clones (RMS-1 and RMS-2) specific to these structures have also been found. These clones contained no coding region and no promising similarities were observed when they were compared to sequences held at GenBank. Mi ni-chromosomes in F. sporotrichioides constitute a mosaic composed of dispersed repeats and unique sequences. This mosaic structure was main tained in all non-interbreeding, genetically isolated strains examined .