Occurrence of Cereal Chlorotic Mottle Virus in Northern Africa

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Abstract
Cereal chlorotic mottle virus (CCMV), a cicadellid-transmitted plant rhabdovirus reported previously only from eastern Australia, was identified as the causal agent of a necrotic leaf streak disease occurring on oats (Avena sativa) and barley (Hordeum vulgare) in southern Morocco. The virus occurred naturally in Setaria verticillata, Agrostis semiverticillata, and Phalaris sp. and was transmitted experimentally by the cicadellid leafhopper Cicadulina bipunctata subsp. bipunctella. The virus caused severe necrotic and chlorotic leaf streak symptoms in oats, durum wheat (Triticum durum), and barley (Hordeum vulgare) but did not infect sorghum (Sorghum bicolor), sugarcane (Saccharum officinarum), any of five maize (Zea mays) cultivars, or bermudagrass (Cynodon dactylon). Oryzopsis miliacea was a symptomless host. In negatively stained leaf-dip preparation, the virus particles measured about 220-250 .times. 60 nm and showed a surface pattern and helical cross-striations similar to those of Australian CCMV. The Moroccan (CCMV-M) and Australian (CCMV-A) virus isolates cross-reacted with each other''s antiserum without spur formation in immunodiffusion tests, and no serological differences between the two virus isolates were detected. In enzyme immune assay (EIA), CCMV-M infection in barley was detectable by homologous immunoglobulin G (IgG) at a sap dilution in excess of 100,000-fold and provided a sensitive method for detecting CCMV infection in plants.