Turnip yellows virus (TuYV) is the most important virus disease of canola (Brassica napus) crops in Australia, where it is wide spread in all grain production regions. It is aphid transmitted with the green peach aphid (Myzus persicae) as the most efficient vector. The typical symptoms of TuYV on infected canola are leaf reddening, distortion or purple leaves and stunting but some cultivars show leaf chlorosis and yellowing or symptomless virus expression. In Victoria, canola crops were surveyed in 2015 and 2016 to determine the occurrence, incidence and distribution of TuYV in different regions (Mallee, Wimmera and Western District) of the state. Virus symptoms present at each site were assessed visually and one hundred samples were collected from each site for analysis. Samples were tested using tissue blot immunoassay (TBIA) and selected samples were confirmed by PCR using TuYV-specific primers. In 2015, TuYV was detected in 19 out of 20 crops and incidence ranged from 2- 70%. In 2016, TuYV was detected in 16 out of 21 crops and incidence ranged from 1-53%. The highest incidence of TuYV was found in the Mallee and Western District in 2015 and in the Mallee and Wimmera in 2016.
The host range of a TuYV isolate originally collected from canola in Deniliquin, NSW was assessed in the glasshouse on canola and turnip (Brassicaceae); chickpea, faba bean, fenugreek, field pea, lentil, narrow leaf lupin and white lupin (Fabaceae); and beetroot, silver beet, spinach and sugar beet (Amaranthaceae). Plants were germinated and maintained in insect-proof cages and inoculated using viruliferous green peach aphids. Plants were harvested approximately one month after inoculation and were tested for TuYV using TBIA. All Brassicaceae and Fabaceae species except for narrow leaf lupin were tested positive and the four Amaranthaceae species tested negative to TuYV.