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Wheat virus diagnostics
Jacob A. Price, Charlie M. Rush, and Ron French
Four common viral pathogens that affect wheat are Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and Wheat mosaic virus (WMoV) transmitted by the wheat curl mite and the aphid transmitted Barley yellow dwarf virus (BYDV). These viruses cause severe losses to wheat production throughout the Western Great Plains region.
How to identify virus infected fields?
Common symptoms of different wheat viruses look identical and are often mistaken for abiotic stresses such as drought and nutrient deficiencies. These symptoms include mosaic or yellowing of the leaves (Fig. 1) which can lead to necrosis and stunting of infected plants.
During early infection symptoms may not be easily visible and plants may have a yellowed appearance which will gradually develop into a mosaic pattern (Fig. 2). Laboratory testing is required for proper identification.
During mite vectored virus infection wheat curl mites move into fields by winds from areas of volunteer wheat and perennial grasses which serve as a green bridge for over summering mites. As the mites transfer these viruses during feeding they create a disease gradient that often begins on the edge of the field and moves inward decreasing in disease severity (Fig. 3). These gradients are not always easy to see, but will increase in severity as the season progresses (Fig. 4). Aphid vectored viruses create circular patterns in infected fields.
Plant samples can be submitted to the Plant Diagnostics Clinic at the Texas A&M AgriLife Research center in Amarillo, TX for virus testing. For complete field testing samples of symptomatic tissue, including roots, should be collected from the north west, south west, north east, and south east areas of the field. A diagnostics sheet should be included with the samples and can be found at: Texas Plant Diagnostic Clinic (THPPDL).
Include the following information on the diagnostics form:
- Name of field owner and submitter
- Address including county
- Contact number
- Information about the field and location (GPS if possible)
- Any and all information included in the diagnostics form will be helpful in determining disease diagnosis