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Title: Leaf Ringspots on Sorbus scopulina L. Associated with Virus-like Particles.

Author
item Robertson, Nancy
item Brown, Kathryn

Submitted to: Phytopathology
Publication Type: Proceedings
Publication Acceptance Date: 4/20/2009
Publication Date: 6/1/2009
Citation: Robertson, N.L., Brown, K.L. 2009. Leaf Ringspots on Sorbus scopulina L. Associated with Virus-like Particles[abstract]. Phytopathology. 99(6):185-186.

Interpretive Summary:

Technical Abstract: Leaf ringspot leaf on Sorbus scopulina L. associated with virus-like particles Nancy L. Robertson and Kathryn Brown (1) USDA-ARS Subarctic Agricultural Research Unit, Palmer AK 99645 Sorbus scopulina L. (Green Mt. Ash), is a native shrub of Alaska that is widely distributed in south central Alaska in natural ecosystems and as an ornamental in public and residential landscapes. In spring, emerging leaves frequently contain noticeable chlorotic ring spots, vein-clearing, and oak-leaf patterns. Erinea and gall forming eriophyid mites were often present on leaves of affected plants. Ultra-thin sections of leaf mesophyll revealed individual to several spherical structures (average diameter 50 nm) enclosed within a membrane. Amorphous inclusions similar to viroplasm-like structures were readily visible. Although particles were not detected from purified “virus” preparations, a prominent protein ~32 kDA was consistently present from only symptomatic leaves. The 32 kD protein did not have a serological affinity with universal potyvirus antiserum or with European mountain ash ringspot-associated virus antiserum on western blots. Double-stranded RNA and “virion” RNA extraction procedures resulted in no distinct bands on agarose gels, and may have been prohibited by the presence of leaf polysaccarides and tannins. The polymerase chain reaction using universal potyvirus primers and cDNA from total RNA extracts resulted in no bands. Symptoms and the associated 32 kDa protein were not detected on the following plants that had been inoculated with sap from affected leaves: Sorbus scopulina, S. aucuparia, Nicotiana benthamiana, Chenopodium amaranticolor, and C. quinoa. The presence of a 32 kDa protein, membrane bound spherical particles, chlorotic leaf symptoms, an association with eriophyid mites, and difficulties with nucleic acid identity, suggests that it is similar to a group of unclassified tentative viruses with a unique morphology of membrane bound particles.