BREAD WHEAT X AGROTRICUM CROSSES AS A SOURCE OF IMMUNITY AND RESISTANCE TO THE PAV STRAIN OF BARLEY YELLOW DWARF LUTEOVIRUS

The Agrotricum line OK7211542 (2n = 56) was immune to the Cloutier iso late, which belongs to the PAV serotype of barley yellow dwarf luteovi rus (BYDV). Through a process of selection for BYDV resistance and thr eshable phenotypes with wheat-like seeds, wheat-like F7-derived lines were obtained from Triticum aestivum\OK7211542 crosses. Some of these were immune to BYDV and had 44 chromosomes. Resistant lines with 2n = 42 chromosomes or slightly higher chromosome numbers were also obtaine d. The low frequency of expression of immunity in the bread wheat back ground over many generations suggests that more than one gene is invol ved. These results are a first step towards the creation of wheat cult ivars immune to BYDV. However, successful introgression will necessita te a transfer of immunity associated with a smaller amount of alien ch romatin in the wheat genome.