Assessment of varietal reaction and breeding for resistance to the yellow-dwarf virus in barley

A series of barley varieties of practical interest in Britain and Western Europe were assessed for reaction to the barley yellow-dwarf virus (BYDV). All proved to be highly susceptible. Fourteen barley selections found to be tolerant to BYDV in the United States were also tested. Although all were tolerant to BYDV when tested in the glasshouse, only two were tolerant under British field conditions. One selection was slightly less tolerant of one virus isolate than it was of another isolate.In progeny from crosses of tolerant and susceptible genotypes, the inheritance of BYDV tolerance was conditioned by a single major gene which showed little or no dominance. Results of preliminary work to introduce BYDV tolerance into the new high yielding European commercial barley varieties, using the backcross method, are reported. Following two or three successive generations of backcrossing, the selection of plants containing the tolerance gene in the heterozygous condition became impossible and the homozygous tolerant genotypes had to be reconstituted to facilitate the selection of plants for further breeding.