Barley CMS detected in Finland in 1976 enabled growing of productive winter-barley F1 hybrids in the European winter-barley zone since 2002
Authors: Ahokas Hannu 
Published: April 2019

My wide crossing program of barley (Hordeum vulgare s.l.) in 1976 yielded a system which could be used to produce F1 hybrid seeds. The genotypes were designated as msm1 (male sterile, maternal), and Rfm1a (restorer of fertility in msm1). I later found 19 other strains with dominant restorer alleles, which were carriers of a fertile cytoplasm. Hence, the restorer genes probably evolved in advance creating an opportunity for the cytoplasm to mutate to male sterility. Cytological studies revealed an uncontrolled secretion of sporopollenin in the sterile anthers, leading to their starvation and sterility. The Rfm1a gene was shown to cause an increase in the cytokinin activity of Fraction 7 in the root sap of barley, regardless of the cytoplasm type. In 1980, I found another male sterile cytoplasm, msm2, whose anther can also be restored by the Rfm1 alleles. The msm2 strain originally had complementary partial restorer genes and was found to be more responsive to such restorers than msm1. In Germany, the Rfm1 gene was recently translocated to a rye (Secale cereale) chromosome to study its response in CMS rye. The msm2 cytoplasm could be distinguished from msm1 with electron microscopy at the early stages of the anthers. The msm1 cytoplasm is not known to be associated with increased disease susceptibility, unlike the T-sterile cytoplasm formerly used to produce hybrid seeds of maize (Zea mays). Hybrid cvs: Seeds of msm1–Rfm1a were first requested from me by Hilleshög AB in Sweden. Hilleshög later became a part of Syngenta. Hilleshög techniques for sugar-beet hybrids were applied by Syngenta breeders to produce hybrid barley seeds. Syngenta introduced the first commercial winter-barley hybrid in the UK in 2002. Their hybrid cvs were marketed to countries growing winter-barley in Europe. The ha yields of their hybrids exceeded those of conventional cultivars or parental lines by about 1000 kg. In Spain, the winter-barley hybrid yielded 21 percent more than the conventional cultivars in 2015, when grown in the field scale. For the 2016 harvest, hybrids were sown in Germany on more than 140000 ha, which reflects 11.6 percent of the total feed barley area. In 2017, Syngenta launched a cashback scheme for, if their hybrid cultivars did not comfortably out-yield the farmer's conventional counterpart that season. Hybrid seeds must be acquired for each sowing. Unlike conventional monogenic barley cultivars, the hybrids exploit genetic variability and heterozygosity. Hybrid winter-barley is the most competitive of winter cereals with the aggressive weed Alopecurus myosuroides in the UK. Thick stems in new hybrids increase lodging resistance. The winter-barley hybrid ‘Wootan’ gave ha yields up to 6000 kg in Tammisaari, though incompletely winter-hardy in Finland. Maturing a month later than the hybrid ‘Hobbit’ and with optimal winterhardiness, winter-barley hybrids could exceed ha yields of 10000 kg in Finland. Some other breeding companies seem to work for hybrid barley, too.