Barley (Hordeum vulgare L.) has been largely neglected in hybrid breeding research of autogamous cereals. The objectives of our study were (i) to study the amount of heterosis, (ii) examine the potential to predict hybrid performance based on midparent values or general combining ability (GCA) effects, and (iii) draw conclusions on the prospects for hybrid breeding in barley. Grain yield performance of 124 hybrids of six‐rowed winter barley, their 27 male and 38 female parental lines, as well as nine line and six hybrid varieties and one hybrid in registration was investigated in plot‐based multi‐environment trials. In a two‐stage analysis, best linear unbiased estimators and variance components of hybrids and parental lines were calculated. Midparent heterosis averaged 11.3%, with a range from 0.7 to 19.9%. Better‐parent heterosis was slightly lower with an average of 9.2%. Maximum commercial heterosis (i.e., the difference between the hybrid performance and the performance of the best line variety) was 7.6%, which clearly underlines the significance of hybrid barley breeding. Accuracy to predict hybrid performance was only moderate based on midparent values (r = 0.46; P < 0.001) and GCA effects (r = 0.38; P < 0.001). Consequently, there is a need for alternative approaches to predict hybrid performance in barley.

Hybridization technology has proven valuable in enhancing yields in many crops, but was only recently adopted in the small grain cereals. Hybrid varieties in barley (Hordeum vulgare) rely on the cytoplasmic male sterility (CMS) system msm1 derived from Hordeum vulgare ssp. spontaneum. The major restorer gene described for the msm1 system is known as Rfm1 and maps to the top of chromosome 6H. To gain further insight into mechanisms underlying male fertility restoration in barley, we used a mapbased cloning approach to identify the nuclear gene involved in the restoration mechanism of this hybridization system. Taking advantage of the available genomic resources in barley in combination with a custom-made non-gridded BAC library developed from a restorer line, we cloned and sequenced the Rfm1 restorer locus. The characterization and annotation of the nucleotide sequence for the Rfm1 restorer allele allowed for the identification of the candidate gene for Rfm1. The Rfm1 locus carries a tandem repeat of a gene encoding a pentatricopeptide repeat (PPR) protein. Surprisingly, Rfm1 belongs to the PLS-DYW subfamily of PPR genes known for their involvement in RNA editing in plants organelles, but that to date have not been identified as restorer genes.

We have confirmed that floatation in salt solutions can be used to separate less-dense, more mealy, lower nitrogen-containing barley from more dense barley with less good malting quality having more steely grains and higher nitrogen contents. This gives breeders a useful tool for massselecting barley with potentially favourable characteristics for malting.We have now shoion that green malt can be fractionated by floatation on sucrose solutions into fractions the least dense ofiuhich contains grains which are the most completely modified.This allows grains that have malted well to be selected. Using this novel technique it has been possible to substantially enrich fractions with green malt corns of the better quality malting variety when mixtures of a good and a less-good malting barley had been micromalted. The green malt fractions can be grown on to maturity. This technique gives breeders a powerful massselection tool for enriching their genetically mixed breeding lines with strains of better malting quality. This approach should be particularly pozverful if applied several times in successive generations. The best results are likely to be obtained by fractionating the barley, collecting the lightest material, micromalting it and then collecting the lightest fraction of the green malt for further propagation.