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

The plant genus Eryngium (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 Entyloma (Entylomatales, Exobasidiomycetes). The combination of morphology, host, and geographic origin did not align with any reported species on Eryngium. This study aimed to identify and characterize this unknown Entyloma sp. ascertain its phylogenetic relationship with other Entyloma 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 Entyloma. Nuc rDNA ITS was also used to attempt the identification of the host. Findings reveal that the unidentified Entyloma sp. forms a distinct and well-supported clade separate from other species on Eryngium. Its closest relatives include En. carmeli, En. eryngii, En. eryngii-cretici, En. eryngii-plani, En. lagoeciae, and En. scandicis. Morphologically, it resembles En. argentinense, En. eryngii-alpini, En. eryngii-cretici, En. eryngii-maritimi, and En. eryngii-plani; however, a combination of host affiliation, geography, and morphology distinguishes the new Entyloma sp. from these five species. Therefore, the new species Entyloma meridionale is described herein. The host plant was confirmed as Eryngium planum. This research increases knowledge of Entyloma diversity and contributes to understanding the dynamics of pathogen movement and potential invasion into new territories.