First report of Beet black scorch virus in the United States.

In October of 2005, sugar beet (Beta vulgaris L.) plants exhibiting symptoms of rhizomania caused by Beet necrotic yellow vein virus (BNYVV) (3) were observed in a production field near Greeley, CO. The roots of seven plants exhibiting moderate to severe symptoms characteristic of this disease were tested using double-antibody sandwich enzyme-linked immunosorbent assay with anti-BNYVV antiserum from rabbits. Of these, only two roots exhibiting the mildest symptoms tested positive for BNYVV (all roots tested negative for the presence of the related Beet soilborne mosaic virus (BSBMV). ‘Hairy’ lateral roots characteristic of the disease were combined from the remaining five roots, ground in phosphate buffer, and the supernatant from the suspension was mechanically applied to leaves of Chenopodium quinoa in an effort to isolate an infectious agent. Five days postinoculation (dpi), yellow lesions with necrotic centers were visible on inoculated leaves, well in advance of those typically observed for BNYVV or ...