Issue: April 2004
Research in Action
Seeking Sick Sorghum Solutions
Research for better Maize and Sorghum
La Trobe University's state-of-the-art confocal microscope commissioned in October 2002 is proving its tremendous worth in biochemical research, according to Dr Leann Tilley.
Collaborative research between La Trobe University botanists and an expert from The Volcani Centre at Israel's Institute of Plant Protection could lead to a better understanding of virus diseases in maize and sorghum.
This stems from advances over the past six months to enhance understanding of Johnson grass mosaic virus which adversely affects both maize and sorghum crops.
One of the world's foremost experts on the disease, Professor Raffi Salomon, retured home at the end of March after working since September with researchers at La Trobe's Department of Botany led by Professor Roger Parish, Head of the Department.
Professor Salomon, a La Trobe distinguished visiting fellow, collaborates with colleagues from a number of universities and other organisations around the world on Johnson grass mosaic virus research.
He was attracted to La Trobe because of the success of Botany Department senior lecturer and researcher, Dr Charles Pallaghy and two of his former students in the Department, Dr Kyung-Soo Kim and Dr Hae-Young Oh, in developing an infectious DNA copy of the RNA that comprises the genetic code of this virus. The DNA copy has been constructed in modular forms that enable mutations in its various genes to be readily made in the laboratory and then reassembled as a virus in plant leaves under containment conditions.
This technique has already provided new information about the function of the genes in Johnson grass mosaic virus.
The Johnson grass mosaic virus, which is common in both Australia and the USA, is transmitted in a 'non-persistent' way by vectors - several species of tiny aphid. This means the aphids spread the virus by inoculation. The virus cannot be spread by contact between plants or from seed - making infections difficult to predict and prevent.
It is particularly dangerous in Queensland where it causes millions of dollars of damage annually to the huge sorghum growing industry in the state's south.
Last year in Israel there was a severe epidemic of viruses from this group of maize and sorghum viruses, with farmers losing between half and all their sweet corn crops. One 800 hectare crop of sweet corn in a small community lost its entire $1 million crop.
Like all viruses, the Johnson grass mosaic virus reduces the vigour of host plants but does not necessarily kill them. In food crops like maize and sorghum it results in considerable reductions in yield.
Professor Salomon said a possible result of his work at La Trobe was that it may now be possible to change the composition of the coat protein that encapsulates the virus to ascertain how it affects the assembly of the entire virus. Once this was achieved, the knowledge could be used to block the passage of the virus through the plant.
He said that Dr Pallaghy's laboratory was the only place where research was sufficiently advanced for this to be done.
'We hope to find some novel information about sulphur-containing amino acid systems in the coat of the Johnson grass mosaic virus which may lead to a way to understand the relationship between the virus and the host plant. This would be a step towards controlling the virus,' Professor Salomon said.
'An important part of the research results from Dr Pallaghy's laboratory is that the information being uncovered there can be applied to other viruses,' he said.
Professor Salomon worked with a number of people while in Australia, including one of Dr Pallaghy's long term collaborators, Dr Denis Presley of the Queensland Department of Primary Industry.
He also worked with Dr Lindsay Sparrow, a CSIRO expert in protein structure and Dr Brendan Rodoni from the Victorian Department of Primary Industries' Institute for Horticultural Development at Knoxfield, developing a procedure for the detection and characterisation of fig mosaic virus. This is essential for the introduction of new fig cultivar into Australia.
On his way back to Israel, Professor Salomon worked with another collaborator, Professor Dallas Seifers of the State University of Kansas, where Johnson grass mosaic virus is a particular problem in Kansas's sorghum crops.•
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