PROGRESS IN IDENTIFYING THE CAUSE OF RAMU STUNT DISEASE OF SUGARCANE

RAMU STUNT first appeared as a serious disease affecting plant growth and ratooning ability at Ramu Sugar Limited in Papua New Guinea during 1985-1986. The disease has not yet been found in Australia, but the insect vector occurs on many Torres Strait islands and at Bamaga and New Mapoon; therefore, Ramu stunt is a major biosecurity risk to the Australian sugar industry. The capability to monitor Ramu stunt disease and prevent or manage potential incursions in Australia would be greatly facilitated by identification of the causal agent, understanding the biology of the disease and the development of a robust diagnostic test. No evidence for a phytoplasma as the causal agent has been obtained. Several lines of evidence suggest that a virus is the causal agent of the disease. Disease-associated nucleic acids were cloned and a preliminary diagnostic test was developed based on cloned RNA sequences with homology to viral RNA-dependant RNA-polymerase. Although only used to screen limited numbers of samples, it is an important step towards the development of a more robust test and the exact identification of the causal agent.