Structure of Ascochyta lentis in Australia revealed with random amplified polymorphic DNA (RAPD) markers

The genetic variation of Ascochyta lentis in Australia was investigated usi ng random amplified polymorphic DNA (RAPD) analysis of 23 isolates. Of the 87 loci assessed, 86 were polymorph ic. The mast closely related isolates w ere from Victoria and South Australia, and they shared identical banding pr ofiles, The most genetically distant isolates were ham South Australia and Western Australia (83% dissimilar). Analysis of molecular variance showed l ow genetic variation between groups of isolates originating from either wit hin or outside Australia (4%). Large variation within each group (96%) indi cated similar pathogen variability within and outside Australia. Partitioni ng of variation within Australian states was shown. Isolates collected with in South Australia were least variable (1%) and isolates collected within W estern Australia were most variable (61%). Increased variation in Western A ustralia is thought to have occurred through multiple introductions and/or the frequent presence of both mating types. Furthermore, two RAPD markers u sed in unison were able to explain over 50% of the variation in isolate pat hogenicity. No RAPD markers were found that discriminated mating type.