CHARACTERIZATION OF WHEATGRASS-DERIVED BARLEY YELLOW DWARF VIRUS-RESISTANCE IN A WHEAT ALIEN CHROMOSOME SUBSTITUTION LINE

Wheatgrass (Thinopyrum intermedium) possesses a high level of resistan ce to barley yellow dwarf virus (BYDV) subgroup I and subgroup II stra ins. A wheat line (P29), in which the 7D chromosome has been substitut ed with a group 7 chromosome from T. intermedium, was examined for the level of resistance to two subgroup I and two subgroup II BYDV strain s. In P29 plants inoculated with the subgroup I PAV strains, the titer of virus in leaf and stem tissue was typically reduced 42 to 52% when compared with the BYDV-susceptible cv. Abe. P29 and 'Abe' had the sam e content of PAV in roots. These results and the absence of detectable virus in inoculated T. intermedium plants indicate that the complete resistance to subgroup I possessed by the wheatgrass has not been intr ogressed into P29. In contrast, P29 was completely resistant throughou t the plant to the subgroup II strains, NY-RPV and NY-RMV, demonstrati ng that the complete resistance to subgroup II in T. intermedium was i ncorporated into P29. Further analysis of this resistance to NY-RPV sh owed that NY-RPV can replicate in mesophyll protoplasts of P29 and 'Ab e', suggesting that this resistance is not operating at the single-cel l level. Molecular marker analysis confirmed that the T.: intermedium chromosome present in P29 is a different group 7 wheatgrass chromosome than that present in L1, a wheat line with BYDV resistance properties similar to those of P29.