Morphological and molecular characterization of Wilsoniana amaranthi (Albuginales, Oomycota) on Amaranthus retroflexus in Iran

White blister rust causal agents, previously assigned to the genus Albugo, are obligate plant pathogens affecting numerous plant families. The genus Wilsoniana has been erected from the genus Albugo to accommodate species infecting hosts in the Caryophyllales. Starting from spring 2018, we observed symptoms resembling white blister rust disease on leaves of Amaranthus retroflexus L. in the northern Iran. The specimens were subjected to molecular study by analyzing cox2, LSU and ITS rDNA sequences and morphological data sets. The results confirmed that the specimens belong to Wilsoniana amaranthi (Schwein.) Y.J. Choi, Thines & H.D. Shin (Albuginales, Oomycota). To our knowledge, this is the first confirmed and documented record of W. amaranthi (ex Amaranthus retroflexus) from both Iran and West Asia. The results of this study will provide a reference for further resolution of W. amaranthi species concept.