Towards the identification of candidate gene(s) for FHB resistance on the 7EL chromosome of Thinopyrum elongatum: design and use of genetic markers.

Thinopyrum elongatum is a wild grass that carries genetic resistance to FHB on the long arm of its chromosome 7E (7EL). 7EL-specific markers as well as 7DL-specific markers for homoeologous wheat sequences were designed to help characterize introgressed material derived from the cross CS-ph1b x CS-7E(7D), a cross that facilitated the introgression of 7E fragments into 7D. As neither wheat nor Th. elongatum genomes are fully sequenced, a cross-walking strategy between wheat and Th. elongatum draft genomic sequences was used. Eight pairs of markers for homoeologous sequence regions of 7EL and 7DL chromosomes plus six individual 7EL-specific markers and four 7DL-specific markers were successfully designed in this project. Those markers were used to characterize BC1F4 progeny from three families derived from the cross CS-ph1b x CS-7E(7D), to help define the introgressed 7E fragments that they contain, in complement with previously published markers. Two of the families contained a smaller 7EL fragment still carrying FHB resistance, when compared with the third family. That smaller introgressed 7EL fragment replaced about half of the 7DL chromosome, based on absence of 7DL markers. The novel 7EL- and 7DL-specific markers as well as the proposed genetic order for novel and previously used markers significantly contributed to the characterization of the introgressed 7EL fragments in the 7DL chromosome.