Identification of a molecular marker linked to an Agropyron elongatum-derived gene Lr19 for leaf rust resistance in wheat

The leaf rust resistance gene Lr19 , transferred from Agropyron elongatum into wheat (Triticum aestivum L.) imparts resistance to all pathotypes of leaf rust (Puccinia recondita f.sp. tritici ) in South-east Asia. A segregating F-2 population from a cross between the leaf rust resistant parent 'HW 2046' carrying Lr19 and a susceptible parent 'Agra Local' was screened in the phytotron against a virulent pathotype 77-5 of leaf rust with the objective of identifying the molecular markers linked to Lr19 . The gene was first tagged with a randomly amplified polymorphic DNA (RAPD) marker S73(728). The RAPD marker linked to the gene Lr19 which mapped at 6.4+/-0.035 cM distance, was converted to a sequence characterized amplified region (SCAR) marker. The SCAR marker (SCS73(719)) was specific to Lr19 and was not amplified in the near-isogenic lines (NILs) carrying other equally effective alien genes Lr9 , Lr28 and Lr32 enabling breeders to pyramid Lr19 with these genes.