Cytogenetic and molecular mapping of the leaf rust resistance gene Lr39 inwheat

Leaf rust, caused by the fungus Puccinia triticina Eriks, is one of the mos t serious diseases of wheat (Triticum aestivum AABBDD, 2n=6x=42) worldwide. Growing resistant cultivars is an efficient and economical method of reduc ing losses to leaf rust. Here we report a new leaf rust resistance gene, Lr 39, transferred from Aegilops tauschii into common wheat. Lr39 conditions b oth seedling and adult plant resistance to the leaf rust pathogen. The inte r- and intra-chromosomal mapping of the Lr39 gene showed that it is differe nt from all previously described Lr genes. We used monosomic analysis for t he inter-chromosomal mapping and wheat microsatellite markers for the intra -chromosomal mapping. The monosomic and ditelosomic analysis indicated that Lr39 is independent of the centromere on the short arm of chromosome 2D. E ight microsatellite markers for 2DS were used for linkage analysis on a pop ulation of 57 F-2 plants derived from a cross of an Ae. tauschii-derived wh eat, cv. Wichita line TA4186 (possessing Lr39), with Wichita monosomics for the D-genome chromosomes. The microsatellite marker analysis confirmed the location of the gene on 2DS. Three markers were polymerphic and linked to the gene. The closest marker Xgwma210 mapped 10.7 cM from Lr39. The locatio n of Lr39 near the telomere of 2DS distinguishes it from the Lr2 and Lr22 l oci, which are located on 2DS proximal to Xgwm210.