Flame Chlorosis: a New, Soil‐transmitted, Virus‐like Disease of Barley in Manitoba, Canada

“Flame Chlorosis” of barley was first observed in two fields of spring barley near Newdale, Manitoba, Canada in late June, 1985. Disease symptoms included leaf chlorosis in a “flame” ‐like pattern, severe stunting, and failure to produce fertile heads. Afflicted plants were found in circular patches in two adjoining fields, and scattered diseased plants were identified in several nearby fields. Surveys in 1986 and 1987 identified scattered diseased plants in a small number of barley fields, most within 50 km of the original Newdale site. In 1988, the disease was identified at many more locations near Newdale, and at two neighbouring sites the disease occurred at levels sufficient to cause economic loss. In addition, flame chlorosis was identified at several locations outside the Newdale region. To date the flame clorosis agent has been transmitted only by planting seed or seedlings in soil where plants with symptoms of flame chlorosis had grown earlier. After transfer to sterile potting medium, afflicted plants continued to produce leaves with symptoms. The cytopathology of flame chlorosis differed from that of the known soil‐borne viruses of cereals. No inclusions of particles were observed, and instead of the characteristic pinwheel‐inclusions, there was massive vesiculation and peripheral distortion of chloroplasts and mitochondria. A set of double‐stranded (ds) RNAs, ranging in size from about 900 to 2800 base‐pairs (bp) and distinct from any described for a known cereal virus, was isolated from plants afflicted with flame chlorosis, while no dsRNA was isolated from healthy tissue of the same cultivar.