The numerous crossing experiments and chromosomal manipulation between rye and wheat is exceptional within the plant kingdom and among the crop plants. Already in 1888 Rimpau (1891) produced the first intergeneric and partially fertile hybrid between hexaploid wheat and diploid rye. Since the first success, a wide range of various combinations of genomes, individual chromosomes and even chromosome segments was established (Schlegel 1990).
The basic aim of rye genome transfer into wheat was to combine the quality characteristics of wheat by the agronomic unpretentiousness of rye. From the many intergeneric hybridizations made between wheat and Aegilops, Triticum, Haynaldia, Hordeum, and Agropyron species, only the wheat-rye combination became of breeding and agronomic value. Less octoploid triticale (AABBDDRR, Fig. 9.1.1) but hexaploid triticale (AABBRR, Fig. 9.1.1) became a new, worldwide grown, and man-made crop plant (Schlegel 1996). After a long period of cytogenetic research and breeding efforts, hexaploid triticale now enlarges the spectrum of cereal crops by high yield, good resistance against diseases and improved protein content.
Among the more than 200 different wheat-alien chromosome addition lines there are complete series of disomic wheat-rye additions, including the adequate disomic telocentric addition lines (Shepherd and Islam, 1988). Individually added chromosomes are available from the rye varieties “Imperial” and “King II”. Incomplete sets exist from the varieties “Dakold” and “Petkus Rye” (Riley and Chapman, 1958). Those addition lines were not only used for first genetic mapping studies in rye but also as source for targeted gene transfer experiment from rye into wheat.
In the past wheat-rye or wheat-Aegilops chromosome substitutions were used for studies of homoeologous relationships between cereal genomes. As better the wheat chromosome compensation by a given alien chromosome as closer the genetic relationship of the chromosome and/or genome can be suggested. As a measure the vitality was used and the successful pollen transmission of the alien chromosome. First reports on spontaneous wheat-rye chromosome substitutions 5R(5A) were given already in 1937 (Kattermann, 1937) and 1947 (O’Mara, 1947). Driscoll and Anderson (1967) reported the substitution of the wheat chromosomes 3A, 3B, 3D, and 1D by rye chromosome 3R. About 20 years later 1R(1D) (Müller et al., 1989) and 1R(1A) substitutions (Koebner and Singh, 1984) were produced in order to improve wheat for baking quality and resistance against diseases. Other wheat-rye chromosome substitutions with breeding relevance are described by Schlegel (1997).
Although a first experimental wheat-rye translocation (4B-2R) was produced already in 1967 (Driscoll and Anderson 1967), introgression of rye genetic information into wheat became most famous by the spontaneous 1RS.1BL wheat-rye translocation (Mettin et. al. 1973, Zeller 1973). Since 1973, in more than 250 cultivars of wheat from all over the world showing this particular type of translocation were described (Schlegel 1997). 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, which is linked with decreased breadmaking quality, good ecological adaptability and yield performance (Schlegel and Meinel 1994), and better nutritional efficiency. 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 (most likely one source, Schlegel and Korzun 1997, Fig. 9.4.1), one in the USA and one in Japan. The variety “Salmon“ (1RS.1BL) is a representative of the latter and the variety “Amigo“ (1RS.1DL) is a representative of the penultimate group (Fig. 9.4.1), while almost all remaining cultivars can be traced back to one or to the other German origin. Another wheat-rye translocation with breeding importance was found in the Danish variety “Viking”. It carries a 4B-5R interchange (Schlegel et al. 1993), causing high iron, copper and zinc efficiency as compared to common wheat.