Characterization of the translocated chromosome using fluorescence in situ hybridization and random amplified polymorphic DNA on two Triticum aestivum Thinopyrum intermedium translocation lines resistant to wheat streak mosaic or barley yellow dwarf virus

Fluorescence in situ hybridization (FISH) was used to determine the breakpoint of the translocation chromosome in two bread wheat (Triticum aestivum) germplasm lines with Thinopyrum intermedium chromatin carrying resistance to either wheat streak mosaic virus (WSMV) or barley yellow dwarf virus (BYDV). In addition, genome-specific random amplified polymorphic DNA (RAPD) markers were used to ascertain the genomic sources of the Th. intermedium chromosomes carrying the WSMV or BYDV resistance. Cl17766, a WSMV-resistant wheat germplasm line derived from induced homoeologous pairing by using the ph1b mutant, had a translocation chromosome composed of the complete 4AL and about 45% of proximal 4AS from wheat, and the entire 4ES of Th. intermedium. The BYDV-resistant translocation line, TC14, derived from tissue culture, had a very short distal segment of 7StL from Th. intermedium terminally attached to 56% of the proximal 7DL. These observations indicate that translocations in these wheat germplasm lines did not involve centromeric breaks and fusion but were a result of homoeologous chromosome recombination.