Location: Grain, Forage & Bioenergy Research
2012 Annual Report
Objective 2. Identify and characterize WSMV determinant(s) responsible for semipersistent transmission by the wheat curl mite.
Objective 3. Develop and evaluate transgenic wheat expressing WSMV non-structural proteins (P1, HC-Pro, P3, NIa) for gene complementation and pathogen-derived resistance to WSMV.
The sequence of TriMV genome was determined and identified as a distinct virus from WSMV. The viral coat protein of TriMV was expressed in bacteria and used to produce a high quality antiserum, providing a much-needed method for high-throughput detection method for the management of TriMV and for germplasm screening in wheat breeding programs. This antiserum also can be used to develop TriMV diagnostic kits by biotech companies.
A new wheat variety, Mace, was developed in collaboration with an ARS plant geneticist researcher at Lincoln, NE which provides significant genetic resistance to WSMV and TriMV. Since both viruses are transmitted by the same vector, mixed infections by WSMV and TriMV are expected to be commonplace. In co-infections, WSMV and TriMV synergistically interact with each other resulting in increased virus concentrations in wheat plants which causes severe effects on wheat growth and yield in susceptible cultivars compared to the resistant cultivar Mace. Therefore, cultivar selection will be an important management strategy for the control of the WSMV/TriMV disease complex in wheat. The double virus resistance of Mace should encourage other wheat breeders to incorporate its virus resistance locus in their breeding programs as well.
The gene for green fluorescent protein (GFP) was inserted into WSMV genome to form bright fluorescent aggregates in infected cells. The availability of GFP-tagged virus has facilitated rapid monitoring of virus presence/spread within a wheat plant during virus infection. GFP-tagged virus can be used as a non-destructive screening tool in the development of new WSMV-resistant wheat varieties. The GFP-tagged virus will also facilitate examining virus-host and virus-vector interactions to better understand the virus life cycle for possible clues to develop new disease management strategies by breaking the disease cycle.
In addition to genetic resistance, plants are known to have innate defenses against invading viruses. In turn, viruses have evolved with proteins to overcome host defense mechanisms. The P1 protein of WSMV was identified as a suppressor of RNA silencing. The coat protein and HC-Pro genes of WSMV were shown to play critical roles in transmission of WSMV by the wheat curl mite.
The outcome of this research provides a new WSMV/TriMV disease management strategy to wheat growers, a new tool for breeders to screen for WSMV resistance, a new diagnostic method for TriMV for extension Plant Pathologists, and advances the understanding of WSMV biology.