The aim of this study was to investigate long‐term genetic trends and the genetic architecture of grain yield, seed characteristics and correlated agronomic traits in triticale. Therefore, a panel of 846 diverse triticale genotypes was assessed for three agronomic and three seed shape‐ and size‐related traits. We observed a high genotypic variation and a high heritability for all traits. Analysing the development of these traits during the last decades revealed a continuous increase for grain yield and thousand‐kernel weight, and a slight increase in seed width. The seed characteristics and thousand‐kernel weight formed a complex of highly positive correlated traits. Genome‐wide association mapping revealed many small‐effect QTL and a few moderate‐effect QTL. The allele frequencies of the moderate‐effect QTL followed the same temporal trends as observed for the phenotype. In line with the phenotypic correlations, we identified several pleiotropic QTL for grain yield, thousand‐kernel weight, seed width and seed area. Our results illustrate the continuous progress achieved in triticale breeding and suggest that triticale seeds have been selected to be more spherical in modern cultivars.

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The quantitatively inherited trait plant height is routinely evaluated in triticale breeding programs as it substantially influences lodging and disease susceptibility, is a main contributor to biomass yield, and is required to improve hybrid seed production by fine-tuning plant height in the female and male parental pools in hybrid breeding programs. In this study, we evaluated a panel of 846 diverse Central European triticale genotypes to dissect the genetic architecture underlying plant height by genome-wide association mapping. This revealed three medium- to large-effect QTL on chromosomes 5A, 4B, and 5R. Genetic and physical fine-mapping of the putative QTL revealed that the QTL on chromosome 5R most likely corresponds to Ddw1 and that the QTL on chromosome 5A is likely to be Rht12. Furthermore, we observed a temporal trend in registered cultivars with a decreasing plant height during the past decades, accompanied by an increasing use of the height-reducing alleles at the identified QTL. In summary, our results shed new light on the genetic control of plant height in triticale and open new avenues for future improvement by breeding.

Key message The comparably low genotype-by-nitrogen level interaction suggests that selection in early generations can be done under high-input conditions followed by selection under different nitrogen levels to identify genotypes ideally suited for the target environment. Abstract Breeding high-yielding, nitrogen-efficient crops is of utmost importance to achieve greater agricultural sustainability. The aim of this study was to evaluate nitrogen use efficiency (NUE) of triticale, investigate long-term genetic trends and the genetic architecture, and develop strategies for NUE improvement by breeding. For this, we evaluated 450 different triticale genotypes under four nitrogen fertilization levels in multi-environment field trials for grain yield, protein content, starch content and derived indices. Analysis of temporal trends revealed that modern cultivars are better in exploiting the available nitrogen. Genome-wide association mapping revealed a complex genetic architecture with many small-effect QTL and a high level of pleiotropy for NUE-related traits, in line with phenotypic correlations. Furthermore, the effect of some QTL was dependent on the nitrogen fertilization level. High correlations of each trait between N levels and the rather low genotype-by-N-level interaction variance showed that generally the same genotypes perform well over different N levels. Nevertheless, the best performing genotype was always a different one. Thus, selection in early generations can be done under high nitrogen fertilizer conditions as these provide a stronger differentiation, but the final selection in later generations should be conducted with a nitrogen fertilization as in the target environment.