Molecular mapping of the leaf rust resistance gene Lr17a in wheat

Wheat leaf rust, caused by Puccinia triticina Eriks., infects millions of acres of wheat (Triticum aestivum L.) and causes leaves to senesce prematurely, which in turn decreases yield by reducing the plant's ability to complete kernel fill. Lr17a, a leaf rust resistance gene in wheat, is present in many wheat varieties available today. The objective of this research was to identify molecular markers linked to Lr17a. Microsatellite-markers were used on a mapping population of 161 F-2 lines made from a cross of Chinese Spring and Thatcher-Lr17a. Capillary fragment analysis was performed and eight markers were linked to Lr17a, of which Xgwm614 and Xwmc407 flanked Lr17a at genetic distances of 0.7 and 2.5 cM respectively. An evaluation of cultivars with and without Lr17a, and grown in the midwestern United States, revealed that multiple alleles were present for all markers and little correspondence between alleles of closely linked markers and Lr17a was observed. Therefore, caution must taken when using them for marker-assisted selection.