The rise of Ramularia from the Mycosphaerella labyrinth

Abstract

In this study we aimed to resolve the Ramularia endophylla species-complex by applying a polyphasic approach involving morphology and multi-gene phylogeny. Eleven partial genes were targeted for amplification and sequencing for a total of 81 isolates representing R. endophylla s. lat. and 32 isolates representing 11 Ramularia species that were previously linked to a Mycosphaerella sexual morph in literature. A Bayesian phylogenetic analysis, as well as a parsimony analysis, was performed on a combined five-locus dataset and the resulting trees showed significant support for three species within the complex, including the previously described R. endophylla and R. vizellae, and one novel species, Ramularia unterseheri. A parsimony analysis was also separately performed with mating-type gene sequences (MAT1-1-1 and MAT1-2-1) and the resulting tree topologies were in accordance with that of the multigene analysis. A bibliographic review of the proposed links between Ramularia spp. and their purported Mycosphaerella sexual morphs is also presented, confirming six connections in Ramularia. In spite of more than 10 000 species having been described in Mycosphaerella, the majority is shown to belong to other genera, suggesting that the taxa identified as Mycosphaerella in much of the plant pathology literature needs to be revisited.