Mini-chromosomes of Colletotrichum spp. infecting several host species in various countries

Pulsed-field gel electrophoresis was used to screen 52 isolates of Colletotrichum spp. for the presence of mini-chromosomes in the size range 200–1200 kb. Mini-chromosomes were observed in all isolates of C. gloeosporioides, and in Australian isolates of C. crassipes, C. dematium and C. truncatum, but not in C. musae, C. lindemuthianum and C. trifolii. The mini-chromosome complements of 36 isolates of C. gloeosporioides from the host genus Stylosanthes were investigated. These isolates were obtained in eight countries from Africa, South East Asia and South America and were from six species of Stylosanthes. Two classes of C. gloeosporioides were discerned on the basis of mini-chromosome content, the first class (Mtype 1) had less than six mini-chromosomes and the other class, (Mtype 2) had greater than six mini-chromosomes including one of 600 kb in size. There was no correlation between Mtype and disease symptom produced, pathogen biotype and the host species and country of origin. These results contrast previous correlations of Mtype with disease symptom, pathogen biotype and host range reported for isolates from Stylosanthes in Australia and suggest that a greater genetic diversity exists in pathogen populations outside Australia