Diversity of Puccinia boroniae assessed by teliospore morphology and restriction fragment patterns of ribosomal DNA

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Preliminary investigations into the diversity of Puccinia boroniae, collected from across southern Western Australia, were conducted by morphological comparison of the teliospores derived from host species Boronia heterophylla and Boronia megastigma, and by restriction enzyme profiling of the internal transcribed spacer (ITS) region of the nuclear rRNA (rRNA) genes of 21 isolates from a variety of different Boronia species and cultivars. Assessment of teliospore morphology provided significant evidence of two distinct rust groups, separated on the basis of their host plant origin. In general, teliospores from Boronia heterophylla had wider apical and basal cell widths, thinner cell walls and apical papilla, than those isolated from Boronia megastigrna. Restriction analysis of the ITS region provided no evidence of intraspecific variation among the 21 isolates; however, one isolate, distinct from the screened population both geographically and by host origin, was shown to have a length variation (insertion) within the ITS region amplified by PCR. The results indicate that subgroups of P. boroniae in Western Australia may be present, with further evidence required to define the level of separation in the population.