**1. Introduction**

Wheat is a global source of food and calories and the main ingredient in many products, with an annual world production volume of around 771 million tons as of 2017 (FAOSTAT, 2017). The bread-making quality is the most important trait for wheat breeding programs worldwide. However, the estimation of bread-making quality is challenging because it is costly and requires a substantial amount of seed for analysis [1]. To overcome these difficulties, researchers have searched for the genetic determinants controlling the trait to enable marker-assisted selection (MAS) [2–4]. However,

the genetic basis of the bread-making quality of wheat is not ye<sup>t</sup> understood and the genes that have been found do not explain the broad variation in this characteristic. High molecular weight (HMW) glutenin genes (*Glu*-*A1*, *Glu*-*B1*, and *Glu*-*D1*) [2], located on the long arm of group 1 chromosomes, are the most well studied among the major genes controlling bread-making quality. A number of markers have been developed to distinguish di fferent alleles of glutenin genes [5–10]. A gene, called wheat bread-making (*wbm*), was identified in wheat, and its elevated expression level in the endosperm during wheat grain development has been demonstrated [11]. Analysis of *wbm* expression in di fferent wheat genotypes resulted in two contrast groups: (1) genotypes with high expression of *wbm* and (2) genotypes with the negligible expression of the gene. A high correlation of *wbm* expression and the values of some quality characteristics have been demonstrated [1,11]. The expression level of *wbm* along with the allelic composition of glutenin genes, and the presence of 1BL.1RS translocation is one of the key determinants of major wheat quality traits coupled with bread-making quality [1]. Analysis of variation in the upstream sequence of *wbm* allowed the identification of one variant, GWseqVar3, which was associated with high *wbm* expression in cultivars with good bread-making characteristics [11]. Based on this knowledge, PCR-based (NWP, [11]) and Kompetitive allele specific PCR (KASP, [10]) markers were developed to specifically identify GWseqVar3. These markers were employed for screening wheat genotypes in di fferent world collections [1,10]. These studies found rare (0% to 36%) occurrences of GWseqVar3 of *wbm* in wheat collections, highlighting the importance of screening of germplasm on *wbm* to improve bread-making quality.

Despite the relative progress in wheat collection screening, the frequency of *wbm* occurrence in hexaploid triticale (×*Triticosecale* Wittmack) (2*n* = 42, AABBRR, wheat × rye hybrid) collections is unexplored. Triticale occupies 4 million hectares worldwide with an approximate production volume of 15 million ton per year, which is comparable to rye production. Triticale is a hardy crop, combining many beneficial traits inherited from both parents, including high yield, increased tolerance to biotic and abiotic stresses, and nutrient-use e fficiency [12–18]. Although triticale is an important crop for biofuel production and forage, application of triticale grains in the bakery industry is limited, with no registered cultivars with good bread-making quality [19]. However, with the current growth in the number of health-conscious people, triticale is becoming more attractive as a human food source [20]. In this context, new breeding strategies are needed to improve triticale end-use characteristics and identification of valuable gene variants located in the A and B genomes.

Study of the *wbm* gene has focused on practical aspects, whereas *wbm* gene origin, evolution, and genomic organization studies are lacking. In their initial publication, Furtado et al. [11] performed PCR screening of wheat progenitor species (*Triticum monococcum*, *Triticum urartu*, and *Triticum turgidum*) to address *wbm* origin but obtained controversial results. The PCR products of the expected size were amplified in some samples of *T. monococcum* (AA genome) and *T. urartu* (AA genome) genomic DNA but not in *T. turgidum* (AABB genome). Because no D-genome donor species (*Aegilops tauschii*) have been used for PCR analysis, the location of the *wbm* gene on wheat A or D genomes was proposed. Rasheed et al. [10], using a Basic Local Alignment Search tool (BLAST) search, proposed the location of the *wbm* gene on chromosome 7AL; whether *wbm* gene can also be found in the D genome has not been studied. Thus, no consistent information about the genomic organization of *wbm* has been reported.

The objective of this study was to examine *wbm* evolution and genomic organization and to use this information in the identification of triticale lines carrying *wbm* for further improvement of the bread-making quality of this crop. From several lines of evidence, we proved the location of *wbm* gene chromosome 7AL and demonstrated considerable diversity in the *wbm* protein sequence between closely related species. Using available genomic data for grasses and PCR analysis with newly developed markers, we found that *wbm* is not an allelic variant but was introgressed from unknown species into the wheat genome. Chinese Spring cultivar has an orthologous *wbm* gene (*wbm-like*), which has negligible expression in grain, and its evolution was accompanied by mobile element insertion. Location of *wbm* in the A genome provides an opportunity for screening the collection of triticale lines possessing A, B, and R genomes, and allowed us to identify three triticale lines possessing this gene.
