A new species of <i>Entyloma</i> (Entylomatales, Exobasidiomycetes) on the ornamental plant <i>Eryngium planum</i> expands the <i>En. eryngii</i> species complex

The plant genus <i>Eryngium</i> (Apiaceae) includes various species used as condiments, ornamentals in gardens, or as elements in floral arrangements. In recent years, there has been a surge in interceptions from South America at U.S. ports of entry, leading to the subsequent destruction of these plants due to the presence of an unidentified species of <i>Entyloma</i> (Entylomatales, Exobasidiomycetes). The combination of morphology, host, and geographic origin did not align with any reported species on <i>Eryngium</i>. This study aimed to identify and characterize this unknown <i>Entyloma</i> sp. ascertain its phylogenetic relationship with other <i>Entyloma</i> species, and verify the identity of the host plant. Morphological and phylogenetic (nuc rDNA internal transcribed spacer [ITS] regions) analyses were performed, in context with available sequences and species of <i>Entyloma</i>. Nuc rDNA ITS was also used to attempt the identification of the host. Findings reveal that the unidentified <i>Entyloma</i> sp. forms a distinct and well-supported clade separate from other species on <i>Eryngium</i>. Its closest relatives include <i>En. carmeli, En. eryngii, En. eryngii-cretici, En. eryngii-plani, En. lagoeciae</i>, and <i>En. scandicis</i>. Morphologically, it resembles <i>En. argentinense, En. eryngii-alpini, En. eryngii-cretici, En. eryngii-maritimi</i>, and <i>En. eryngii-plani</i>; however, a combination of host affiliation, geography, and morphology distinguishes the new <i>Entyloma</i> sp. from these five species. Therefore, the new species <i>Entyloma meridionale</i> is described herein. The host plant was confirmed as <i>Eryngium planum</i>. This research increases knowledge of <i>Entyloma</i> diversity and contributes to understanding the dynamics of pathogen movement and potential invasion into new territories.