Effectiveness of the wheat Lr22b, Lr34, and Lr37 genes for adult plant resistance to leaf rust in West Siberia and the cytophysiological basis of their action

The effectiveness of genes for adult plant resistance to leaf rust has been explored in southern West Siberia by the examples of common wheat cv. Thatcher (Tc), which carries the Lr22b gene, and its nearisogenic lines TcLr34 and TcLr37 . Lr22b is inefficient; Lr34 slows down the disease development at a mean daily temperature below 16°C, but is poorly efficient at temperatures above 20°C. Lr37 provides high resistance under all conditions. At the heading stage, the TcLr34 and TcLr37 lines show similar components of partial resistance to rust: reduction in the number and sizes of spots and sporogenesis suppression. Cytological examination has revealed partial suppression of the formation of Puccinia triticina infection signs both at the surface and in tissues (appressoria and haustoria) without hypersensitive reaction (HR). Defense mechanisms in the form of an oxidative burst induced by contacts of appressoria with stomata and callose-lignine appositions are discovered. The lignin autofluorescence color differs from fluorescence that is characteristic for HR-accompanied combinations in TcLr34 and TcLr37 . The Lr34 and Lr37 genes exert a pleiotropic action on pathogenesis.