Cereal chlorotic mottle virus — a rhabdovirus of Gramineae in Australia transmitted by Nesoclutha pallida (Evans)

An undescribed rhabdovirus was found in eight species of Gramineae at locations extending over 1000 km of the tropical and subtropical Australian east coast. The incidence in maize was usually low but sometimes reached 50% in susceptible hybrids. Cereal chlorotic mottle virus (CCMV) was shown experimentally to infect Avena sativa L., Digitaria ciliaris (Retz.) Koeler, Dinebra retroflexa (Fahl.) Panz., Echinochloa colona (L.) Link., Eleusine coracana (L.) Gaertn., Eleusine indica (L.) Gaertn., Hordeum vulgare L., Triticum aestivum L. and Zea mays L. Symptoms in all hosts began as chlorotic striations, but were often reduced to a fine chlorotic mottle in subsequent growth. After a 3-day acquisition, 50% of individuals of the cicadellid Nesoclutha pallida (Evans) transmitted CCMV in consecutive test feeds with only occasional failures, but some insects then failed to transmit for up to 30 days before death. The time between acquisition and first transmission was 11–24 days and the time for symptom development in the plant was 11–21 days. The virus was acquired and transmitted by both nymphs and adults and by males and females. Transmission continued through the moult to adult. In negative stain the particles were bullet-shaped, 214 by 75 nm, with a net-like surface pattern and core width of 28 nm. There were c. 48 helix cross-striations and 52 surface projections around the full perimeter of bacilliform particles when viewed after brief fixing with glutaraldehyde before staining.