RNAi Mediated Silencing of Endogenous Wheat Genes eIF4(iso)E-2 and eIF4G Induces Resistance to Potyviruses Wheat streak mosaic virus and Triticum mosaic virus

Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are two viruses affecting wheat in the Great Plains of the United States. Current disease management strategies incorporate  deployment of resistant varieties, mite vector control and various cultural practices; however, it is not fully effective. Both of these viruses belong to the family Potyviridae and use host eukaryotic initiation factors in order to facilitate replication of their genomes. We evaluated the use of RNAi to silence eIF4(iso)E2 and eIF4G to interrupt this process in order induce resistance to these wheat viruses. RNAi expression vectors were independently created from the sequences of the wheat genes eIF4E(iso)2 and eIF4G. Immature embryos of the wheat cultivar ‘Bobwhite’ were independently co-transformed by biolistic particle delivery system with RNAi expression vectors and pAHC20, which contains the bar gene for glufosinate selection. All progeny have undergone PCR and RT-PCR analysis. Progeny were mechanically inoculated with the viruses.  A consistent stable resistance response was demonstrated in three transgenic lines of eIF4(iso)E2 construct and four transgenic lines of eIF4G, each derived by single seed descent. T₆ progeny were co-infected with WSMV and TriMV continue to be resistant. Traditional crosses have been performed with the winter wheat ‘Overley.’ Effectiveness of the RNAi construct has been evaluated using Real-time PCR.  Results show up to 18-fold reduction in viral titer in the transgenic lines, the F1 cross and the BC1F1 in compared to control plants. This research provides evidence that a single transgene can provide resistance to multiple viruses having great potential benefits to breeders and producers.