Development and Validation of Thinopyrum elongatum–Expressed Molecular Markers Specific for the Long Arm of Chromosome 7E

The ditelocentric addition line CS-7EL of the spring wheat (Triticum aestivum L.) cultivar Chinese Spring (CS) contains the long arm of the chromosome 7E from Thinopyrum elongatum (CS-7EL), which confers high resistance to Fusarium head blight. It is of great interest to breeders to integrate the resistance locus (loci) from Th. elongatum into commercial wheat varieties. The objectives of this study were to identify candidate genes expressed from the 7EL chromosome of CS-7EL, to develop 7EL-specific molecular markers, and to validate their usefulness for characterizing recombination between one of the group 7 chromosomes of wheat and Th. elongatum. High-throughput sequencing of Fusarium graminearum-infected and control CS and CS-7EL cDNA libraries was performed using RNA-Seq. A stepwise bioinformatics strategy was applied to assemble the sequences obtained from RNA-Seq and to create a conservative list of candidate genes expressed from the foreign chromosome 7EL. Polymerase chain reaction primer pairs were designed and tested for 135 candidate genes. A total of 48 expressed molecular markers specific for the chromosome 7EL were successfully developed. Screening of progenies from two BC1F2 families from the cross CS-7E(7D) x 2*CSph1b showed that these markers are useful for characterizing recombination events between the chromosomes 7D from wheat and 7E from Th. elongatum.