Interactions Between Resistance Genes In Wheat \u3ci\u3eTriticum aestivum\u3c/i\u3e L. And Wheat Curl Mite Populations \u3ci\u3eAceria tosichella\u3c/i\u3e Keifer (Eriophyidae)

Wheat curl mite (WCM) (Aceria tosichella Keifer) is a major pest of winter wheat (Triticum aestivum L.), being the only known vector of three damaging plant viruses, Wheat streak mosaic virus, Triticum mosaic virus, and High Plains wheat mosaic virus. This wheat-mite-virus complex causes significant yield loss globally. Management has been mostly through cultural practices to reduce mite build up in volunteer wheat, thereby reducing the spread of viruses. Host plant resistance to WCM has also been used as an important management strategy for this wheat-mite-virus complex. However, WCM is a cryptic species complex, resulting in great variability in WCM responses to resistance genes in wheat. Also, the stability of WCM resistance has been questioned because of previous adaptation to one mite resistance gene (Cmc3). Changes in virulence of mite populations were examined after field selection and long-term (i.e., 6-8 months and 12 months) exposure to different mite-resistant wheat varieties TAM 107 (Cmc3), TAM 112 (Cmc3+Cmc4) and Byrd (Cmc4). Mite populations were allowed to go through multiple generations on resistant varieties to estimate their adaptation potential. Mite population counts and leaf curling symptoms were evaluated after short (14 days) and extended (28 days) mite infestation to estimate the stability of antibiosis and tolerance traits. Results indicate that the effectiveness of antibiosis on WCM populations was reduced with long-term mite exposure to TAM 112 but not for Byrd. This adaptation to the resistance in TAM 112 was only evident for the 12-month colony at the extended 28-day test period. In contrast, plant tolerance remained stable and effective throughout the 12-month colony period. The transcriptome-level responses of wheat to continued mite feeding and exposure of subsequent mite generations to plant defenses were examined. Results indicate potential mechanisms of resistance for Byrd containing the Cmc4 gene. Action of phytohormones, combined with lipid signaling and membrane integrity appear to play a role in response to WCM after 10-day-post-infestation (dpi). A higher number of molecular functions are activated at 10 dpi compared to previous work done at 1 dpi for this resistant variety. In addition, the importance of the genes located in the sub-genome D of the wheat in response to mite feeding is identified. Advisors: Gary L. Hein and Joe Loui