Triticum aestivum (bread wheat) is an important cereal crop not only in Canada but also worldwide. The pathogen Fusarium graminearum is responsible for causing the disease fusarium head blight and generates yield loses and mycotoxin contaminated grains, including in wheat. A strategy used to mitigate this problem is through the production of FHB resistant wheat varieties by crossing strongly resistant germplasms from closely related wheat species. Thinopyrum elongatum is a wild wheat grass that carries genetic resistance to FHB on the long arm of its chromosome 7E (7EL). Previous work has developed genetic material by crossing Chinese Spring (CS) ph1b line with a CS-7E(7D) substitution line to facilitate introgression of 7E fragments from Thinopyrum into the 7D chromosome of wheat. In the first part of this project a genetic order for previously designed 7EL- and 7D- specific markers was proposed using IWGSC RefSeq v1.0 and was used to characterize the introgressed material from the above cross. Progeny from BC1F7 and BC1F5 families of different lineages were genotyped and phenotyped to characterize regions of introgression which were estimated to be at least 42 and 22 Mbp respectively. Gene expression analysis was also performed for selected 7EL genes. Results showed that the expression of selected 7EL genes present within the introgressed fragments were highly variable between the three families characterized as well as within families. It was also observed that the 7EL introgressed progeny had variable expression when compared to the addition line CS-7EL. Additionally gene expression analyses were also performed using 7D genes. These results showed that there was variation in 7D gene expression between the 7EL introgressed progeny and the controls CS-Fg and addition line CS-7EL-Fg. Possible explanations regarding the variation in gene expression includes differential methylation patterns, silencing of genes in the progeny, alteration of repetitive sequences or activation of transposable elements. Further research will be needed to test these hypotheses.

Triticum aestivum (bread wheat), one of the most globally important cereal crops, is vulnerable to fusarium head blight (FHB). The disease is mainly associated with the pathogen Fusarium graminearum and generates yield losses and mycotoxin contaminated grains with low quality. One possible solution to overcome this problem is the production of FHB resistant wheat varieties by crossing with strongly resistant germplasm from either wheat or closely related species. Thinopyrum elongatum is a wild grass that carries genetic resistance to FHB on the long arm of its chromosome 7E (7EL). In the first part of this research project, five Th. elongatum accessions were characterized for their response to F. graminearum infection. In the second part, BC1F4 progeny derived from the cross CS-ph1b × CS-7E(7D) were characterized to better define the 7E fragments introgressed into the 7D chromosome. Progeny were screened with a series of known 7E-specific genetic markers and for their FHB resistance. Among the 43 wheat plants tested, twelve FHB resistant progeny were shown to carry a similar, smaller 7EL introgressed fragment based on genetic marker screening. To characterize further the introgressed 7EL fragments, additional 7EL-specific markers as well as 7DL-specific markers for homoeologous wheat sequences were designed. As neither wheat nor Th. elongatum genomes were fully sequenced at the time, this made the designing procedure challenging; a cross-walking strategy between wheat and Th. elongatum draft genomic sequences was used. Twelve pairs of markers for homoeologous sequence regions of 7EL and 7DL chromosomes plus six individual 7EL- and four 7DL-specific markers were successfully designed. Nine novel 7EL-specific markers were associated with the smallest 7EL fragment carrying FHB resistance. That smallest introgressed 7EL fragment replaced approximately half of the 7DL chromosome, based on the absence of 7DL markers in some progeny. The novel 7EL- and 7DL-specific markers as well as the proposed genetic order for novel and previously designed markers contributed greatly to the characterization of the introgressed 7EL fragments in the 7DL chromosome. Further analysis of progeny from the next generations of these plants and from other families will be required to confirm the results and possibly obtain much smaller 7EL fragments.