Schnell (1959) provided a first report on rye with cytoplasmic-genic pollen sterility. He found in selfed lines of European rye varieties numerous offsprings showing pollen sterility. However, the inheritance of the character was not as clear (Kobyljanskij, 1969). More intensive crossing experiments, however, demonstrated the presence of cytoplasmic-genic inheritance of male sterile plants in rye (Geiger and Schnell, 1970). Systematic screenings and genetic studies carried out at the University of Hohenheim (Germany) since 1966 among 46 European, 1 Argentinean and 96 accessions from Iran yielded a cytoplasmic male sterile sample from Argentina, further on designated as line with “Pampa” cytoplasm. It became important as main constituent for the German hybrid-breeding program of rye and it behaves analogous to the “Texas” cytoplasm in corn.
It is easy to find non-restorer plants for reliable sterility maintenance, whereas fully effective fertility restorers occur rather seldom. On the other hand, there are several other cytoplasms reacting in a similar, but not identical manner as the “Pampa” cytoplasm, when tested for male sterility in crosses with specific pollinators. Adolf and Neumann (1981) and Steinborn et al. (1993) detected a second type of CMS cytoplasm. Compared to the “Pampa” type it is classified as “Vavilov” type. The latter is difficult to maintain, while it was easy to find restorers for it – vice versa for the “Pampa” cytoplasm.
Restorer genes were detected not only in exotic accessions but also in several European varieties. The frequency of gametes with restorer genes ranged between 10 and 20 % across all accessions. During the last decade the genes were genetically mapped and described in detail (Glass et al., 1995; Dryer et al., 1996; Miedaner et al., 2000).
Systems of chromosomal male sterility have not attained any practical meaning. Although there are ms genes, suitable markers, and balanced tertiary trisomics with very low male transmission (as in the BTT system of barley), but those prerequisites could not be combined to an efficient breeding program (Sybenga, 1985).