Identification of a dominant stripe rust resistance gene YrXY on chromosome 6R in hexaploid triticale

Breeding resistant cultivars is the most effective strategy to control stripe rust in cereal crops. The hexaploid triticale line Xinyi is highly resistant to stripe rust at the seedling and adult plant stages. A segregating F₂ population derived from a cross between Xinyi and the susceptible hexaploid triticale cultivar Zhongsi1048 was assessed to understand the genetic architecture of stripe rust resistance. Genetic analysis revealed that an all-stage resistance in Xinyi, temporarily designated YrXY, was caused by a single dominant gene. Based on bulked segregant RNA sequence (BSR-seq) analysis, YrXY was identified at 868.82-883.98 Mb on chromosome 6R. By constructing a genetic map based on newly developed KASP markers, the YRXY locus was reconfirmed and narrowed to a 1.4 cM genetic interval, correspondingly to a 2.03 Mb genomic interval (871.47-873.50 Mb). Thirty-two high-confidence genes were predicted in this genomic region, and the non-specific serine/threonine protein kinase gene SECCE6Rv1G0451190 was the most likely candidate gene based on sequence and expression analysis. Genotyping using KASP markers closely linked to YRXY in a segregating population (F₅) derived from a cross of Xinyi and common wheat line L83 revealed that the stripe rust resistance gene YrXY was stably expressed in a wheat-triticale background. We developed a closely linked, breeder-friendly PCR marker that can be used in marker-assisted breeding for stripe rust resistance in both triticale and wheat.