MINICHROMOSOMES OF COLLETOTRICHUM SPP INFECTING SEVERAL HOST SPECIES IN VARIOUS COUNTRIES

Pulsed-field gel electrophoresis was used to screen 52 isolates of Col letotrichum spp. for the presence of mini-chromosomes in the size rang e 200-1200 kb. mini-chromosomes were observed in all isolates of C. gl oeosporioides, and in Australian isolates of C. crassipes, C. dematium and C. truncatum, but not in C. musae, C. lindemuthianum and C. trifo lii. The mini-chromosome complements of 36 isolates of C. gloeosporioi des from the host genus Stylosanthes were investigated. These isolates were obtained in eight countries from Africa, South East Asia and Sou th America and were from six species of Stylosanthes. Two classes of C . gloeosporioides were discerned on the basis of mini-chromosome conte nt, the first class (Mtype 1) had less than six mini-chromosomes and t he other class, (Mtype 2) had greater than six mini-chromosomes includ ing one of 600 kb in size. There was no correlation between Mtype and disease symptom produced, pathogen biotype and the host species and co untry of origin. These results contrast previous correlations of Mtype with disease symptom, pathogen biotype and host range reported for is olates from Stylosanthes in Australia and suggest that a greater genet ic diversity exists in pathogen populations outside Australia.