Genetic and Phenotypic Diversity of European Triticale: GWAS of Yellow Rust Resistance and Agronomic Traits

Triticale (x Triticosecale Wittmack) is an interspecific hybrid of wheat and rye. It is a promising grain and forage crop that thrives in poorer soils and low-input farming systems. It can serve as a viable alternative to traditional small grains such as wheat and barley, bringing diversity to crop rotations and enhancing biodiversity in agricultural practices. Although the original aim was to develop a hybrid combining the best traits of both parents, namely, the quality of wheat and the improved tolerance to (a)biotic stress factors of rye, the outcome turned out differently. Today, its susceptibility to evolving pathogens, particularly Puccinia striiformis f. sp. tritici (Pst), the causal agent of yellow (stripe) rust, poses a challenge for its cultivation. This study evaluated 280 triticale accessions, including cultivars and advanced breeding lines of predominantly European origin, across five agroecological zones over two to three growing seasons. Phenotypic assessments focused primarily on resistance to yellow rust (YR). Other relevant phenotypic traits, such as plant height and heading date, have also been recorded. A Genome-Wide Association Study (GWAS) was performed using a dataset of 14,529 DArTseq SNP markers to determine the genetic control of the interested traits. Phenotypic screening revealed considerable variation in YR severity between years, locations and triticale genotypes, with similar results found for plant height and heading date. On the genetic level, there was substantial variation between the genotypes. Still, no significant population structure was visible as the genotypes were mainly grouped according to the donor breeding institute. The GWAS revealed a total of 12 significant marker-trait associations to the phenotypic traits of YR resistance, plant height and heading date; half of these markers are located in the rye subgenome. The results of this study confirm the presence of exploitable genetic diversity in the European triticale germplasm, representing a valuable resource for research and breeding programmes aimed at improving disease resistance and adaptation.