Revisiting the Taxonomy of Polymyxa graminis: Phylogenetic Insights Reveal Cryptic Diversity and Novel Tetramyxa Species in Poaceae and Wetland Hosts

 

Student/in: Alex Schwarz, BSc
Termin: 18.03.2025, 15.30 Uhr
Ort: Seminarraum 2 (ICT-Gebäude

1. Prüfer/in: Univ.-Prof. Mag. Dr. Sigrid Neuhauser
2. Prüfer/in: Ao. Univ.-Prof. Mag. Dr. Ursula Peintner​​​​​​​
Vorsitzende/r: Univ.-Prof. Mag. Dr. Susanne Zeilinger-Migsich

 

Interessierte Kolleginnen und Kollegen sind herzlich willkommen!

 

Abstract

Polymyxa graminis is a soil-borne obligate parasite which infects the roots of Poaceae (grasses). Molecular studies place P. graminis within the Plasmodiophorida, an order in the robustly supported class Phytomyxea (Rhizaria). Although P. graminis plays an important agricultural role as a vector of plant viruses, its intraspecies taxonomy remains to be resolved. It is yet unclear whether P. graminis is one species with several ecotypes (formae specialis), or if it is a species complex. The broad range of different host and habitats make it more difficult to apply existing species concepts which centre around host specificity.

In this study we tried to resolve these open questions in the species complex of P. graminis. For this we systematically collected and tested roots from 29 Poaceae species sampled along environmental and elevational gradients for presence/absence of P. graminis. We generated 41 rDNA sequences from P. graminis s.l.. Phylogenetic analyses of the most comprehensive dataset of Phytomyxea sampled to date resulted in two well-supported clades Polymyxa (including P. graminis f.sp. temperata) and Tetramyxa (including P. graminis f. sp. tepida). Furthermore, we provide the first report of a plasmodiophorid parasite from Cyperaceae (sedges), which is likely a yet undescribed species.