Abstract

The lack of suitable genes in existing wheat germplasm collections makes breeding for specific traits a difficult task. Although tolerance to barley yellow dwarf viruses (BYDV) has been reported in wheat accessions, there are no suitable levels of resistance to BYDV, so genes are sought from wild relatives. The ability for Thinopyrum species to inhibit replication of BYDV makes them attractive sources of resistance for germplasm development. Breeding programs are exploiting Thinopyrum species to develop wheat germplasm resistant to BYDV. The transfer of genes from Thinopyrum into wheat by wide crossing and selecting progeny using molecular markers identified suitable material to some strains of BYDV. The implementation of molecular marker technology has been useful for rapid selection of wheat lines with resistance to some strains of BYDV in a breeding program. However, it is now clear that Thinopyrum species contain a number of resistance genes on different genomes and homoeologous chromosomes. In order to achieve broad-spectrum resistance to the various serotypes of the BYDV complex it will be best to combine a number of these genes. Research efforts are now focussed on introgressing other genes from Thinopyrum into wheat that provide resistance to several additional strains of BYDV. Molecular markers will play an important role during selection in pyramiding genes to develop wheat germplasm with broadspectrum BYDV resistance.