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Mycobiology. 2016 Jun;44(2):93-8. doi: 10.5941/MYCO.2016.44.2.93. Epub 2016 Jun 30.

Phylogenetic and Morphological Identification of the Novel Pathogen of Rheum palmatum Leaf Spot in Gansu, China.

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Gansu University of Chinese Medicine, Lanzhou 730000, China.
Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA.


A new leaf spot disease was observed on leaves of Rheum palmatum (Chinese rhubarb) in Northwest China (Gansu Province) starting in 2005. A Septoria-like fungus was isolated and completion of Koch's postulates confirmed that the fungus was the casual agent of the leaf spot disease. Morphology and molecular methods were combined to identify the pathogen. The fungus produced conidiomata pycnidia and the conidia were 2~5 septate, 61.2~134.1 µm in length and 3.53~5.3 µm in width, which is much larger than the known Spetoria species that infects Polygonaceae species. Phylogenic analysis of the internal transcribed spacer region confirmed that this Spetoria-like fungus is within the Spetoria genus but distinct from known Spetoria species. Together, these morphological and phylogenetic data support that the R. palmatum infecting Spetoria strain is a newly-described plant pathogenic species.


Internal transcribed spacer rDNA; Novel pathogen; Rheum palmatum; Taxonomy

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