First and fifth authors: United States Department of Agriculture–Agriculture Research Service (USDA-ARS) and Department of Plant Pathology, second author: USDA-ARS and Department of Agronomy and Horticulture, third author: Department of Entomology, and fourth author: Department of Plant Pathology, University of Nebraska–Lincoln, Lincoln 68583.
Triticum mosaic virus (TriMV), the type member of the newly proposed Poacevirus genus, and Wheat streak mosaic virus (WSMV), the type member of Tritimovirus genus of the family Potyviridae, infect wheat naturally in the Great Plains and are transmitted by wheat curl mites. In this study, we examined the ability of these viruses to infect selected cereal hosts, and found several differential hosts between TriMV and WSMV. Additionally, we examined the interaction between WSMV and TriMV in three wheat cultivars at two temperature regimens (19 and 20 to 26°C), and quantified the virus concentration in single and double infections by real-time reverse-transcription polymerase chain reaction. Double infections in wheat cvs. Arapahoe and Tomahawk at both temperature regimens induced disease synergism with severe leaf deformation, bleaching, and stunting, with a 2.2- to 7.4-fold increase in accumulation of both viruses over single infections at 14 days postinoculation (dpi). However, at 28 dpi, in double infections at 20 to 26°C, TriMV concentration was increased by 1.4- to 1.8-fold in Arapahoe and Tomahawk but WSMV concentration was decreased to 0.5-fold. WSMV or TriMV replicated poorly in Mace at 19°C with no synergistic interaction whereas both viruses accumulated at moderate levels at 20 to 26°C and induced mild to moderate disease synergism in doubly infected Mace compared with Arapahoe and Tomahawk. Co-infections in Mace at 20 to 26°C caused increased TriMV accumulation at 14 and 28 dpi by 2.6- and 1.4-fold and WSMV accumulated at 0.5- and 1.6-fold over single infections, respectively. Our data suggest that WSMV and TriMV induced cultivar-specific disease synergism in Arapahoe, Tomahawk, and Mace, and these findings could have several implications for management of wheat viruses in the Great Plains.