Durum wheat with Yr78 and common wheat with Yr78 and Yr36 in coupling show enhanced stripe rust resistance

The adult plant resistance gene Yr78 provides durable resistance to stripe rust (Puccinia striiformis f. sp. tritici) in common wheat but has not been detected in durum wheat or other tetraploid wheat accessions. To introduce Yr78 into durum wheat, we introgressed it into the cultivar Kronos by marker-assisted backcrossing. Field evaluation revealed that the introgression of Yr78 reduced the mean infection type from 6.27 to 3.79 and the mean disease severity from 63.91% to 38.71%. Using germplasm excluding other resistance quantitative trait locus found in Kronos, we quantified the effect of Yr78 and observed that Yr78 alone significantly reduced stripe rust infection type and severity by 14.72% and 25.76%, respectively (p < 0.05), but the infection type (IT) score remained high (mean IT = 6.75), indicating Yr78 should be combined with additional resistance genes for enhanced effectiveness. To achieve this, we combined the linked Yr36 and Yr78 in coupling in common wheat to enhance the Pst resistance and facilitate their simultaneous deployment in breeding programs. The combined Yr36–Yr78 genes significantly reduced the mean IT score by 42.86% compared to lines without these two genes. To enhance the value of this combination, we also combined the linked Yr36–Yr78 with seedling resistance genes Yr5 and Yr15, so all four genes can be transferred in a single cross. Molecular markers for these genes are provided to facilitate their deployment. The germplasm developed in this study has been deposited to GRIN-Global to accelerate its use in durum and common wheat breeding programs.