Submitted to: Cereal Rusts and Mildews Conference European and Mediterranean Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/2/1996
Publication Date: N/A
Technical Abstract: Processes of host specialization, adaptive changes in life cycle, and morphologic changes are important in the evolution and taxonomy of rust fungi. The leaf rusts of Hordeum with aecial hosts in the Liliaceae are a group that has complex patterns of adaptive radiation and life cycle changes. DNA sequence analysis of ribosomal rDNA regions has provided a useful means of examining phylogenetic relationships among closely related rust fungi. This study begins to examine relationships among the rusts of Hordeum, microcyclic rusts of the Liliaceae, and other leaf rusts of the Gramineae using DNA sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal rDNA gene repeat. Parsimony analysis of the ITS DNA sequence data indicated that P. hordei is part of a larger clade which includes other heterecious barley leaf rusts (U. reichertii and U. viennot-bourginii) and the microcyclic rust complex U. scillarum. All members of this clade have their evolutionary origins in the Middle East. Although P. hordei from cultivated barley is currently distributed worldwide, other rusts in this clade remain localized to the Middle East. The North American barley leaf rust, U. hordeinus, is phylogenetically very distinct and clusters with P. allii as well as several North American representatives of the P. recondita species complex. Isolates of P. recondita clustered into four distinct groups that are consistent with differences in morphology and geographical centers of origin.