Cranberry plants bearing disfigured, scarred fruit were reported by growers in the major cranberry-growing region of central Wisconsin in July 2012. Plants bearing scarred fruit have since been observed in Massachusetts and New Jersey. Three complementary methods provided evidence of Tobacco streak virus (TSV) in symptomatic plants: (i) leaves and scarred berries tested positive for TSV by double-antibody sandwich enzyme-linked immunosorbent assay; (ii) quasi-isometric particles approximately 33 nm in diameter were extracted from leaves of symptomatic plants and visualized using transmission electron microscopy; and (iii) coat protein gene sequence analysis revealed 94 to 99% nucleotide similarity with reference TSV sequences. In newer cultivars, 99% of uprights with scarred berries tested positive for TSV. In older cultivars, 31% of uprights with scarred berries tested positive for TSV and the remaining 69% of uprights with scarred berries tested positive for Blueberry shock virus. TSV overwintered in cranberry plants, and leaves, pollen, and fruit tested positive for TSV the year following symptom occurrence. Attempts to inoculate cranberry using infected pollen or sap as inoculum failed, but several herbaceous hosts tested TSV positive following mechanical inoculation. Phylogenetic analysis of the coat protein gene of 26 TSV isolates from various cultivars of cranberry in Wisconsin, New Jersey, and Massachusetts revealed diversity. This work provides information that will be useful in understanding the epidemiology of TSV in cranberry and in the development of management strategies.
Bibliographical noteFunding Information:
We thank our cranberry grower-cooperators, Wisconsin crop consultants, and Ocean Spray crop consultants for use of field sites and assistance with sample collection; and A. Cramer, K. Adams, V. Kartanos, A. Charkowski, A. Witherell, T. German, E. Saalau-Rojas, R. Serres, and B. Martin for assistance with sample collection and processing and helpful discussions. This research was funded by the National Institute of Food and Agriculture, United States Department of Agriculture, under ID number WIS01653; Wisconsin Cranberry Board, Inc.; Ocean Spray Cranberries, Inc.; Cranberry Institute; Vaughan-Bascom Professorship of the Department of Plant Pathology, University of Wisconsin-Madison; and the Senator Robert Caldwell Graduate Fellowship of the College of Agricultural and Life Sciences, University of Wisconsin-Madison.
© 2016 The American Phytopathological Society.
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