Leaf Rust Resistance Gene LR34 is Involved in Powdery Mildew Resistance of Cimmyt Bread Wheat Line Saar

Abstract

The CIMMYT bread wheat line Saar has a high level of adult plant resistance to leaf rust (LR, caused by Puccinia triticina) and stripe rust (YR, caused by P. striiformis f. sp. tritici) based on Lr34/Yr18 in combination with additional minor resistance genes. Because Saar also has good partial resistance to powdery mildew (PM, caused by Blumeria graminis f. sp. tritici), experiments were set up to test whether Lr34 could be involved in its resistance to PM. A population of 113 recombinant inbred F6 lines from a cross between Saar and Avocet-YrA was tested for all three diseases. Correlations among the disease data for LR, YR and PM were strong and highly significant, suggesting that the cross segregated for at least one common genetic factor that affected the resistance to all three diseases. Strong correlations with leaf tip necrosis (LTN), a phenotypic marker for Lr34, indicated that this gene was indeed involved in the PM resistance of Saar. Disease testing of near-isogenic lines for Lr34 and Lr46 in the genetic background of Avocet-YrA and YrLrPrl1 in the background of Lalbahadur showed that all three genes were associated with significantly reduced levels of LR, YR and PM compared to their susceptible genetic backgrounds. It is concluded that resistance to both rust and PM is not only confined to Lr34, but could be a general phenomenon of LTN-associated resistance genes, including Lr46 and YrLrPrl1