The interest in cytoplasmic male sterility (cms) for hybrid seed production in winter barley has become stronger after a new sterility was discovered in Hordeum spontaneum L. (Ahokas, 1979, 1980). Studies and trials of this system have been started at many locations in the world (Ahokas, 1982; Ahokas and Hockett, 1981; Lehmann, 1984). Cms lines given to us by Ahokas have not shown any great difficulties that limit their broad use. Transfer of sterility into winter barley appeared to be easy. Fertility restorers were a problem with this system, but restoration was shown to be controlled by a single dominant character.
By means of backcrossing and combination breeding, we have established that the winter barley varieties Mirag, Maguelone, and Alpha have the restorer gene (Rf).
Backcrossing to two-rowed varieties Alpha, Jubiley 100, N 3353, Maguelone, Robur, N 823, and N 39/81 has been used for creation of cms lines. Male sterility was tested in different climatic and agronomical conditions in 1985 through 1991 and the results showed that sterility is stable. The cms lines obtained in varieties Alpha, Obzor, Ruen, and Krassi 2 (Table 1) after 10 backcrosses were shown to possess morphological and economic characters similar to those of normal cytoplasm lines, indicating that cytoplasm had no effect on spike length, spikelet number in ear, and vegetation period duration. A slight reduction in stem length in the Alpha and N 39/18 cms lines was recorded.
Using backcrosses to a fertility restorer, 62 new lines have been obtained. They were evaluated for some morphological characters and adaptivity (Table 2). The biometrical characteristics indicated that they had medium stem height, long spikes, and low sterility, which have proved to be preconditions for expression of heterosis effects. The restorer lines obtained from heterosis breeding could be used in a conventional program as well.
Presumably, restorer production for only one cytoplasm could lead to undesirable results in relation to disease resistance. For that reason in conventional and established breeding of good restorers, an attempt is being made to place restorer genes in normal cytoplasm genotypes (N RfRf).
The success of future seed production to a great extent will depend on stability of the cms systems. Preliminary studies showed that the system based on Hordeum spontaneum cytoplasm is stable and reliable for the conditions in Bulgaria.
Ahokas, H. 1979. Cytoplasmic male sterility in barley. III. Maintenance of sterility and restoration of fertility in the msml cytoplasm. Euphytica 28:409-419.
Ahokas, H. 1980. Cytoplasmic male sterility in barley. VII. Nuclear genes for restoration. Theor. Appl. Genet. 57:193-202.
Ahokas, H. 1982. Cytoplasmic male sterility in barley. XI. The msm2 cytoplasm. Genetics 102:285-295.
Ahokas, H., and E. A. Hockett. 1981. Performance tests of cytoplasmic male-sterile barley at two different latitudes. Crop Sci. 21:607-611.
Lehmann, L. C. 1984. Where is hybrid barley today? Barley Genetics IV, Edinburg:772-776