Detection of Wheat Streak Mosaic Virus in four pasture grass species in Australia

M.H. Ellis*, G.J. Rebetzke, W.M. Kelman, C.S. Moore and J.E. Hyles

*marc.ellis@csiro.au

Wheat streak mosaic virus (WSMV) has been recently been identified in Australia (Ellis et al., 2003), where it was detected in glasshouse-grown wheat plants and in a summer wheat crop at the Ginninderra Experimental Station, Canberra. An extensive survey of the area around the wheat crop was conducted to assess the spread of the virus into adjacent pasture species. Samples of grasses were harvested and then tested for WSMV by RT-PCR (French and Robertson, 1994). The survey involved testing circa 1600 samples from a 200 m radius of the infected wheat crop. A number of the grasses sampled showed leaf streaking and mottling characteristic of WSMV in wheat (see Murray et al. 1998 for leaf symptoms in wheat). Using RT-PCR, fourteen WSMV-positive samples were found on four common grass weeds of pastures in southern Australia (Fig. 1), including African lovegrass (Eragrostis curvula (Schrad.) Nees), whorled pigeon grass (Setaria verticillata (L.) Beauv.), spike goosegrass (Eleusine tristachya Lam.) and a panic (Panicum sp.). The latter was not identified to the species level, due to the lack of floral structure in the sample. The 271 bp RT-PCR products were sequenced and were over 99% identical to the WSMV isolate from wheat (Ellis et al., 2003).

Figure 1. RT-PCR detection of WSMV in grass species samples. 
The 271bp product is diagnostic for the presence of WSMV. 
The wheat controls used are described by Ellis et. al. 2003.

The wheat curl mite (Aceria tosichella), the vector of WSMV (Murray et. al. 1998) was also identified on pasture grasses in the sampling area (Bruce Halliday, Pers. Comm.). WSMV is known to have a wide host range amongst the Poaceae (Oldfield and Proeseler, 1996). However, this is the first report of this virus in African lovegrass (Eragrostis curvula) and three spike goosegrass (Eleusine tristachya). These grasses commonly occur within Australian pastures, suggesting that Australian pastures can act as potential sources of WSMV infection for adjoining cereal crops.

References

Ellis MH, Rebetzke GJ, Chu P, 2003. First report of the wheat streak mosaic virus in Australia. New Disease Reports 7 [http://www.bspp.org.uk/ndr/].

French R, Robertson NL, 1994. An RT-PCR method for the detection of the wheat streak mosaic virus. Journal of Virological Methods 49, 93-100.

Murray TD, Parry DW, Cattlin ND, 1998. A Colour Handbook of Diseases of Small Grain Cereal Crops. London, UK: Manson Publishing.

Oldfield GN, Proeseler G, 1996. Eriophyoid mites as vectors of plant pathogens. In: Lindquist EE, Sabelis MW, Bruin J, eds. Eriophyoid Mites: Their Biology, Natural Enemies and Control. Amsterdam, The Netherlands: Elsevier Science BV, 259-275.

The British Society for Plant Pathology