Pustula echinaceae sp. nov. (Albuginales, Oomycota), a new species causing white blister rust disease on the ornamental plant Echinacea purpurea (L.) Moench

The order Albuginales includes the causal agents of white blister rust disease, which affect a wide range of weedy plants, both cultivated and wild. The genus Pustula is one of the five major lineages of white blister rusts identified to date. It causes disease on asterids, the largest group of flowering plants. Pustula is represented by several phylogenetically distinct, host-specific lineages, many of which remain formally undescribed. In this study, samples of white blister rust collected from the economically valuable ornamental plant Echinacea purpurea were investigated. Phylogenetic analysis based on COX2 mtDNA, supported by ITS and LSU rDNA sequence comparisons, combined with detailed morphological investigations, revealed a distinct and independent lineage, separate from previously known species of Pustula . As a result, a new species, Pustula echinaceae sp. nov., infecting Echinacea purpurea , is described and illustrated.