VARIATION IN GENOME ORGANIZATION OF THE PLANT-PATHOGENIC FUNGUS COLLETOTRICHUM-LINDEMUTHIANUM

The genome structure of Colletotrichum lindemuthianum in a set of dive rse isolates was investigated using a combination of physical and mole cular approaches. Flow cytometric measurement of genome size revealed significant variation between strains, with the smallest genome repres enting 59% of the largest. Southern-blot pro files of a cloned fungal telomere revealed a total chromosome number varying from 9 to 12. Chro mosome separations using pulsed-field gel electrophoresis (PFGE) showe d that these chromosomes belong to two distinct size classes: a variab le number of small (< 2.5 Mb) polymorphic chromosomes and a set of unr esolved chromosomes larger than 7 Mb. Two dispersed repeat elements we re shown to cluster on distinct polymorphic minichromosomes. Single-co py flanking sequences from these repeat-containing clones specifically marked distinct small chromosomes. These markers were absent in some strains, indicating that part of the observed variability in genome or ganization may be explained by the presence or absence, in a given str ain, of dispensable genomic regions and/or chromosomes.