PCR-based molecular marker for the Bdv2 Thinopyrum intermedium source of barley yellow dwarf virus resistance in wheat

Because of the importance of BYDV in wheat production worldwide, and given the difficulties of bioassaying for resistance, a molecular marker was deve loped for the resistance known as Bdv2 that originates on the long arm of c hromosome 7Ai1 of Thinopyrum intermedium. This resistance was identified in a partial amphiploid line TAF46, a disomic addition line to wheat (L1), a telosomic addition line (7Ai1 L), and a series of recombinants and transloc ations. A RAPD (random amplified polymeric DNA) marker for the resistant ge rmplasm was cloned and sequenced, and primers were designed against that se quence to produce a sequence characterised amplified region (SCAR) marker. A single PCR product is produced only with genotypes carrying the resistanc e from any of the available recombinants. The cloned sequence, recommended primers, and PCR protocols are described. The usefulness of the marker has been demonstrated for following Bdv2 in segregating wheat breeding germplas m, with the imminent release of a BYDV-resistant cultivar.