Stem rust resistance in durum wheat
Our research objective is to identify new resistance genes in durum wheat that are effective against TTKSK and other significant stem rust pathogen races that could be utilized in durum breeding. We characterized 8,000 accessions for stem rust response in the field (Debre Zeit, Ethiopia, and St. Paul, MN). Accessions with resistant to moderately resistant responses in multiple field evaluations were evaluated at the seedling stage for resistance to races TTKSK, TRTTF, TTTTF, JRCQC, TKTTF, and six representative U.S. races. We identified 438 durum accessions resistant to moderately resistant in all field evaluations. Among the field-resistant accessions, 273 were resistant to all races used in seedling evaluations. Accessions susceptible at the seedling stage are being evaluated for the presence of adult plant resistance genes. The highest frequencies of resistant lines include landraces from East and North Africa (Ethiopia and Egypt) and advanced breeding lines and cultivars from North America (Mexico and USA). DNA markers will be performed to identify the presence of durum stem rust resistance genes, including Sr13, Sr8155B1, Sr11, and Sr8a. Nineteen resistant accessions were selected to investigate the genetics of TTKSK and TRTTF resistance. Results from evaluating F2 and F2:3 generations from biparental crosses revealed that resistance to race TTKSK was conferred mostly by one or two genes with dominant and recessive actions. Additional resistance genes were identified when populations were evaluated against race TRTTF. A bulk segregant analysis approach is being used to map the resistance in selected lines using the 90K SNP platform.