Race Specificities of Puccinia triticina Effectors and their Effects on Wheat

Puccinia triticina Eriks is the causal agent of wheat leaf rust and is a major economic player in the profitability of wheat production.  Each year new races are isolated from wheat growing areas of the US Great Plains.  Races with virulence to newly released resistance genes are selected for by large acreages of single varieties.  Unlike other cereal rust pathogens, the alternate host required for sexual recombination is not present and the pathogen replicates asexually by an uredinial spore cycle. So the question arises, where does the genetic variation come from?  We have identified an avirulence leaf rust gene associated with a hypersensitive response in wheat with the Lr26 disease resistance gene.  We have sequenced the cDNA of six different races of leaf rust and identified alleles of the AvrLr26.  Because of the obligate biotrophic nature of P. triticina, we also were able to sequence wheat cDNA and examined gene expression associated with the six races.  This is providing a unique avenue to study both host and race specific pathogen responses to infection.