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Molecular analysis of novel FHB resistance

Wang, L., Forseille, L., Boyle, K., Francis, T., Pan, Y., Liu, Z., Li, Y., Zaharia, L.I., Ouellet, T. and Fobert, P. 2016. Molecular analysis of novel FHB resistance. Third Annual Science Meeting of the Canadian Wheat Alliance, Saskatoon, June 27-28, 2016.

Abstract

Fusarium head blight (FHB) caused by Fusarium graminearum (Fg) is one of the most prevalent diseases of wheat (Triticum aestivum L.). Due to their poor agronomics and low yield, it has proven difficult to move existing sources of FHB resistance into adapted Canadian varieties. Recently, germplasm developers at Agriculture and Agri-Food Canada (AAFC) generated a novel cultivar, FL62R1, which has high FHB resistance, good agronomics and quality, and resistance to rust and mildew. However, little is known on the molecular and genetic nature of this novel source of FHB resistance and its relationship to existing FHB resistance sources. Understanding the molecular basis of resistance has the potential to accelerate the deployment of novel and native sources of FHB resistance with better agronomics and end-use quality. In this study, multiple approaches were applied to characterize resistance in FL62R1 with the goal of introgressing desirable alleles into Canadian elite wheat varieties. In addition to FL62R1, the well-known FHB resistant line, Sumai3, and two Canadian elite wheat varieties with moderate to low FHB resistance, Stettler and Muchmore, were analyzed. Disease assessment revealed that Sumai3 has the highest type II FHB resistance, with FL62R1 being moderately resistant to Fg, and Stettler and Muchmore being more susceptible. Microscopic observations demonstrated that Fg growth was limited to the inoculated spikelets in the resistant varieties and did not spread to rachis and uninfected spikelets. Rachilla and rachis of resistant varieties displayed strong cell wall-related defense responses, such as callose deposition and lignification. These results indicate that rachis of the resistant varieties play an important role in the type II FHB resistance. To better understand the molecular basis of type II resistance among the four varieties, Fg-infected spikelets and rachis were collected separately for RNA-Sequencing, metabolomics and hormone profiling analysis. Preliminary results suggest that multiple defense-related pathways and responses contribute to type II FHB resistance in Sumai3 and FL62R1.

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