The origin of the alien chromosome was intensively discussed by genetic and historical reasons. It turned out that basically four sources exist - two in Germany (it might be one source, see Schlegel and Korzun 1997, one in the USA and one in Japan. The variety 'Salmon' (1RS.1BL) is a representative of the latter Tsunewaki 1964) and the variety 'Amigo' (1RS.1AL) is a representative of the penultimate group Beronsky et al. 1991; The et al. 1992, while almost all remaining cultivars can be traced back to one or to the other German origin (Zeller 1973; Blüthner and Mettin 1977).
In 2014, Howell et al. (2014) decribed lines not carrying the distal wheat region (1RS and 1RSwr) showed significant improvements in grain yield and canopy water status compared to near isogenic lines carrying the distal wheat segment (1RSww and 1RSrw), indicating that the 1RS region replaced by the distal wheat segment carries the beneficial allele(s). NILs without the distal wheat segment also showed higher carbon isotope discrimination and increased stomatal conductance, suggesting that these plants had improved access to water.
In 2011, about 1.050 varieties carry the 1RS.1BL translocation, about 100 varieties the 1RS.1AL translocation, and about 30 varieties a 1R(1B) substituion (cf. database attached). Their most important phenotypic deviation from common wheat cultivars is the so-called wheat-rye resistance, i. e. the presence of wide-range resistance to races of powdery mildew and rusts (Bartos and Bares 1971; Zeller 1973), which is linked with decreased breadmaking quality (Zeller et al. 1982), good ecological adaptability and yield performance Rajaram et al. 1983; Schlegel and Meinel 1994, Singh et al. 2008, Zhai et al. 2016).
In China, since the 1960s stem rust has been basically controlled, because the varieties with 1B.1R translocation that are widely used have still showed effective resistance to stem rust. Nevertheless, a new race Ug99 could be a potential threat even to Chinese wheat production because the 1B.1R translocation with Sr31 is highly susceptible to the race (Howel et al. 2014).