Puccinia triticina is a wheat obligate biotrophic pathogen causes severe yield losses worldwide. Generally, single, major gene resistance has been used to provide protection against infection, but because of high rates mutation in the pathogen, resistance genes have a limited window of effectiveness. Broad spectrum, minor resistance wheat genes appear to be involved in the biotrophic interaction of rust and wheat. Thus, an EMS mutagenesis approach was taken to identify other genes involved in host-pathogen interactions. M1 lines of leaf rust susceptible Thatcher were infected with P. triticina race BBBD to identify individuals with reduced infection. One line, 531, was found to have an induced hypersensitive-like response when infected with spores. The response was pronounced at 4 dpi and further developed into necrotic lesions by 14 dpi. Newly emerged, non infected leaves did not have lesions. cDNA from F2:3 families are being sequenced and the results of bulk segregate analysis will be presented.