RNAi Mediated Silencing of Endogenous Wheat Genes Eif(iso)4E-2 and eIF4G Induces Resistance to Potyviruses.

Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are two viruses affecting wheat in the Great Plains of the United States. The current disease management strategy incorporates the 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 eIF(iso)4E-2 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 eIF(iso)E-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. To determine viral resistance, the progeny were mechanically inoculated with the viruses.  A consistent stable resistance response was demonstrated in three transgenic lines of eIF(iso)4E-2 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 ‘Karl 92.’ 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 and has great potential benefits to both breeders and producers.