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The impact of Triticum mosaic and Wheat streak mosaic viruses' co-infection on spring wheat performance

Dalitso Yabwalo: South Dakota State University

<div><em>Triticum</em> <em>mosaic virus</em> (TriMV), a fairly new wheat (<em>Triticum aestivum</em> L.) pathogen, largely co-infects winter wheat with <em>Wheat streak mosaic virus</em> (WSMV), a well-known pathogen that can cause severe yield losses in winter wheat. The combined impact of TriMV and WSMV on spring wheat is not well known. A field study was initiated to investigate the differential performance of diverse spring wheat genotypes against WSMV, TriMV and a mix of WSMV-TriMV, and to determine the effect of WSMV-TriMV co-infection on yield, shoot development and chlorosis in spring wheat. Seven hard red spring wheat cultivars and three elite breeding lines were inoculated with WSMV, TriMV and a 1:1 mix of WSMV and TriMV at Feeke’s stage 4. Virus severity (Vscore) was rated on a 1-5 scale where 1=no disease and 5=severe chlorosis. Most of the inoculated genotypes developed moderate to severe symptoms but ‘Select’ consistently responded better than the rest to all viral inocula with predicted cumulative probabilities of 0 and 0.23 at Vscore=5 and Vscore≤2.5, respectively. The rest of the cultivars were above 0.75 probability at Vscore≤2.5. A negative Pearson’s correlation was observed between yield and Vscore (<em>r</em>=-0.78, <em>p</em>≤.0001). Overall yield reduction by WSMV-TriMV was 75% compared to 35% and 39% reduction due to WSMW and TriMV, respectively. Independently, the two viruses were not significantly different from each other for yield and Vscore. These results suggest that spring wheat performance can severely suffer from WSMV-TriMV co-infection. Therefore, breeding efforts should be devoted to developing resistance to both viruses.</div>