Virus-Induced Gene Silencing Suggests (1,3;1,4)-β-glucanase Is a Susceptibility Factor in the Compatible Russian Wheat Aphid–Wheat Interaction

The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a significant insect pest of wheat (Triticum aestivum L.) and has a major economic impact worldwide, especially on winter wheat in the western United States. The continuing emergence of new RWA biotypes virulent to existing resistance genes reinforces the need for more durable resistance. Studies have indicated that resistance in previously susceptible plants can be produced by knock-down of susceptibility genes or other genes involved in host plant susceptibility. Therefore, investigation into genes involved in compatible RWA–wheat interactions could be a feasible approach to achieving durable RWA resistance. The objective of this study was to test whether silencing (1,3;1,4)-β-glucanase, previously observed to be highly induced in susceptible compared with resistant wheat during aphid infestation, would confer resistance to a susceptible wheat genotype. Barley stripe mosaic virus–mediated virus-induced gene silencing was employed to test whether (1,3;1,4)-β-glucanase is involved in the susceptible reaction of ‘Gamtoos-S' (GS). Controlled infestation with U.S. biotype RWA2 was done to assess aphid reproduction and host symptom development. Aphids on (1,3;1,4)-β-glucanase-silenced plants reproduced less per day and had longer prenymphipositional periods than those on control GS plants. Furthermore, the (1,3;1,4)-β-glucanase-silenced plants exhibited less chlorosis and greater dry weight compared with GS. Aphid reproduction and host plant symptom development showed linear relationships with (1,3;1,4)-β-glucanase transcript levels. Our results suggest that (1,3;1,4)-β-glucanase is required for successful infestation by the RWA and may be a susceptibility factor that could be exploited as a potential target for RWA resistance breeding.