Earlier this year, the Queensland Department of Primary industry (DPI) pathology team received samples of soybean with virus-like symptoms. Diseased plants displaying strong chlorotic mottle on leaves and leaf crinkling (see images below) were scattered through the crop.
While the samples tested positive in a polymerase chain reaction (PCR) test for potyvirus, the actual species remained a mystery. Subsequent sequencing of the PCR product showed siratro 1 virus Y as the closest match (Genbank accession DQ098900).
Soybean plants from Ayr region infected with siratro 1 virus Y, displaying chlorotic mottle and crinkled leaf surface (photos supplied by local agronomist).
The siratro 1 virus Y had only previously been reported from Australia in siratro weed (Macroptilium atropurpureum), and this is the first known record of infection in soybean. Little is known about the biology or potential impact of this virus on soybean or other grain legumes.
It is likely to be transmitted by aphids, and siratro weed may be an important source of the virus if the weed is growing near to cropping areas. No immediate action is recommended but DPI pathologists ask growers and agronomists to keep a look out for disease symptoms in Queensland soybean crops in the coming season.
If you see concerning symptoms in soybean crops, please contact plant pathologist Murray Sharman ([email protected], 0467 721 400) or Lisa Kelly ([email protected], 0477 747 040) for further information on disease diagnosis.
Siratro is a legume native to tropical America and is widely used in coastal Queensland and New South Wales as a pasture plant, but is considered an environmental weed elsewhere, including roadsides, waterways, disturbed sites and farming land that is not used for pastures (images DPI).