Relationships Among Stem‐Rust Genes on Wheat Chromosomes 2B, 4B, and 6B

Abstract

Pathological and genetic studies involving ‘Chinese Spring’ substitution lines showed that the varieties ‘Kenya Farmer’ and ‘Sapporo No. I’ both carry the Sr7a gene for resistance to Puccinia graminis tritici on chromosome 4B (VIII). ‘Hope’ carries a different allele, Sr7b . The presence of the resistance gene Srll on chromosome 6B (X) of both ‘Timstein’ and Kenya Farmer was confirmed, as was the existence of two alleles for resistance at the Sr9 locus on chromosome 2B (XIII) of ‘Red Egyptian’ (Sr9a) , Kenya Farmer (Sr9b) , and ‘Kenya 117A’ (Sr9b). ‘Thatcher’ chromosome 2B carries an independently inherited gene designated Srl6 . The existence of alleles for resistance to stem rust confers an advantage on hybrid wheat, which can have two different resistance genes at a single locus.