Rhexocercosporidium matricariae sp. nov. – a new pathogen on the medicinal plant Matricaria recutida

A new disease was observed on chamomile plants (Matricaria recutita L.) in various professionally cultivated fields in 2016 and 2017. From symptomatic stems and leaves the fungal species described here was isolated repeatedly. Koch´s postulates using in planta experiments were fulfilled by inoculation of chamomile plants proving the fungus to be the causal agent of the disease. Morphological studies and phylogenetic analyses using ITS, LSU, and tef-1α sequences suggested that the fungus represents a new species within the genus Rhexocercosporidium (Helotiales). The sequences of other loci including β-tubulin and rpb2 were also obtained and deposited in GenBank for potential uses in further studies. Detailed phylogenetic analyses as well as a description of the growth parameters, morphological structures and comprehensive illustrations of the new species, Rhexocercosporidium matricariae, are presented. All species so far assigned to Rhexocercosporidium are compared and discussed.