Stable resistance to Wheat streak mosaic virus in wheat mediated by RNAi

Wheat streak mosaic virus (WSMV) is one of the major wheat viruses found in the Great Plains of the USA. Cultural practices are the primary methods of disease management, though not fully effective. Although genetic resistance is available, it is temperature sensitive and is sometimes closely linked with traits having negative agronomic effects. Alternative approaches to viral resistance are clearly needed. RNA interference (RNAi) has been shown to play a role in viral defense response and has been successfully used as a biotechnological tool to preprogram viral resistance in transgenic plants. In this work, a portion of the coat protein of WSMV was used as a hairpin construct and was co-transformed with pAHC20-bar to elicit viral resistance. Eleven WSMV RNAi independent transgenic events were obtained. Thirteen T1 lines were resistant as evident by the lack of viral RNA within the tissue. Beginning in the T2 generation, single-plant lineages were selected, selfed, and evaluated for resistance and presence of the transgene until the T5 generation. Families were then evaluated for the presence of the transgene, presence of the selectable marker, and WSMV resistance. Each of the lines in the T5 generation were resistant to the virus. Generational selection has maintained expression of the transgene and resistance to WSMV.