Stripe rust resistance in wild wheat Aegilops tauschii Coss.: genetic structure and inheritance in synthetic allohexaploid Triticum wheat lines

Studies on natural plant variability for biotic (e.g. disease) and abiotic (e.g. drought) stress resistance/tolerance may provide valuable insights into the use of wild genetic resources for breeding purposes, as such phenotypes are often the product of local adaption. To elucidate the mechanisms underlying stripe rust resistance in wild wheat Aegilops tauschii Coss., the D genome progenitor of common wheat (Triticum aestivum L., AABBDD genome), we studied the distribution of stripe rust resistant accessions among the intraspecific lineages that were found previously through DNA polymorphism analysis (TauL1, TauL2, and TauL3) and the expression of resistance in synthetic allohexaploid lines (AABBDD genome) derived from an artificial cross between Ae. tauschii and a cultivar of Triticum turgidum L., the AB genome progenitor of common wheat. Forty-two, out of the 104 Ae. tauschii representative accessions, showed resistance in a field test. The resistant accessions were from Armenia, Azerbaijan, Iran, and Turkmenistan, and belonged to TauL1 (five accessions) and TauL2 (37 accessions). Most TauL1 and TauL2 accessions parental to the synthetic lines showed resistance in the seedling inoculation tests. Thus, TauL1 and TauL2 lineages may be sources of stripe rust resistance for common wheat improvement. In contrast, virtually all synthetic lines examined (32 lines in total), including 22 lines derived from the resistant TauL2 accessions, were susceptible under field conditions, indicating that field resistance of Ae. tauschii to stripe rust may not be inherited in the synthetic offspring. Seedling inoculation tests showed that the synthetic lines are mostly susceptible, but five had weak resistance.