Novel germplasm providing resistance to barley yellow dwarf virus in wheat

The lack of suitable genes in existing wheat germplasm collections makes br eeding for specific traits a difficult task. Although tolerance to barley y ellow dwarf viruses (BYDV) has been reported in wheat accessions, there are no suitable levels of resistance to BYDV, so genes are sought from wild re latives. The ability for Thinopyrum species to inhibit replication of BYDV makes them attractive sources of resistance for germplasm development. Bree ding 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 t echnology has been useful for rapid selection of wheat lines with resistanc e to some strains of BYDV in a breeding program. However, it is now clear t hat Thinopyrum species contain a number of resistance genes on different ge nomes and homoeologous chromosomes. In order to achieve broad-spectrum resi stance to the various serotypes of the BYDV complex it will be best to comb ine a number of these genes. Research efforts are now focussed on introgres sing other genes from Thinopyrum into wheat that provide resistance to seve ral additional strains of BYDV. Molecular markers will play an important ro le during selection in pyramiding genes to develop wheat germplasm with bro ad-spectrum BYDV resistance.