Summary

Plant viruses cause significant economic losses in agriculture and may pose biosecurity risks to lucerne production and seed exports. A previously unknown plant rhabdovirus, Alfalfa dwarf virus (ADV), was detected in 2010 infecting commercial lucerne fields in Argentina and Uruguay with 90-95% disease incidence, causing > 50% yield loss and significantly reducing seed production. Due to its potential economic impact in Australia, ADV is listed as high-risk pathogen in the Australian Fodder Biosecurity Plan. In collaboration with Argentine researchers, we have recently determined the complete genome sequence of ADV. Building on this data, we propose to 1) develop a sensitive molecular diagnostic assay for ADV, 2) apply this assay to conduct targeted surveys of Australian lucerne crops and preserved samples from previous surveys to determine if ADV is present, 3) conduct collaborative research in Argentina to study ADV genetic diversity and epidemiology to identify natural insect vectors, potential for seed transmission and alternative crop & weed hosts, and 4), develop a biosecurity plan and integrated control measures based on this combined new knowledge. This will place the Australian lucerne industry in an excellent position to protect lucerne from this exotic virus disease and increase certified seed exports to South America.

Program

Pasture Seeds

Research Organisation

The University of Queensland

Objective Summary

Major objectives of the proposed research project will be
1) Develop a sensitive molecular diagnostic assay for ADV,
2) Apply this assay to survey Australian lucerne crops,
3) Conduct collaborative research in Argentina to study ADV genetic diversity and epidemiology to identify natural insect vectors, potential for seed transmission and alternative crop & weed hosts, and
4) Develop a biosecurity plan and integrated control measures based on this combined new knowledge.
The research project will provide an answer to the question of whether ADV is present in Australian lucerne. Alfalfa dwarfism symptoms described overseas have never been recorded in Australia, and it is therefore unlikely that it occurs here. However, using a specific diagnostic assay to demonstrate this will provide scientific evidence of area freedom for this virus. If on the other hand, ADV was detected, immediate biosecurity measures could be implemented in an attempt to contain and eradicate the disease. It should be noted that ADV in Argentina can occur in mixed infection with Alfalfa mosaic virus (AMV); therefore available samples known to be infected with AMV will be re-analysed for presence of ADV.
Another expected outcome of the research is detailed scientific knowledge regarding the epidemiology of ADV. This information will be used to develop biosecurity strategies including the adoption of the diagnostic assay to help prevent ADV from entering Australia.