A map of the barley genome consisting of 295 loci was constructed. These loci include 152 cDNA restriction fragment length polymorphism (RFLP), 114 genomic DNA RFLP, 14 random amplified polymorphic DNA (RAPD), five isozyme, two morphological, one disease resistance and seven specific amplicon polymorphism (SAP) markers. The RFLP-identified loci include 63 that were detected using cloned known function genes as probes. The map covers 1,250 centiMorgans (cM) with a 4.2 cM average distance between markers. The genetic lengths of the chromosomes range from 124 to 223 cM and are in approximate agreement with their physical lengths. The centromeres were localized to within a few markers on all of the barley chromosomes except chromosome 5. Telomeric regions were mapped for the short (plus) arms of chromosomes 1, 2 and 3 and the long (minus) arm of chromosomes 7.

Two genes conferring resistance to the barley stripe rust found in Mexico and South America, previously identified as race 24, were mapped to the M arms of barley chromosomes 7 and 4 in a doubled haploid population using molecular markers and the quantitative trait loci (QTL) mapping approach. The resistance gene on chromosome 7 had a major effect, accounting for 57% of the variation in disease severity. The resistance gene on chromosome 4 had a minor effect, accounting for 10% of the variation in trait expression. Two pairs of restriction fragment length polymorphism markers are being used to introgress the resistance genes to North American spring barley using molecular marker-assisted backcrossing.

Malting quality and winter-hardiness in barley are 'ultimate' phenotypes composed of constituent quantitatively inherited traits. A synthesis of molecular-marker hnkage data and field phenotyping to reveal the location of quantitative trait loci (QTL) may assist in the development of winter-habit malting barley varieties. One-hundred doubled haploid progeny from a winter x spring cross were evaluated under fall and spring-planted conditions. Malting quality phenotypes and a 76-point map were used to identify QTL and to assess the effect of springand autumn-sowing on QTL expression. Many QTL efl'ects were common to both environments and corresponded to QTL detected in other barley germplasm. While there were significant difl'erences in the magnitude of efl'ects across environments, there were no changes in the favourable allele phase. QTL efl'ects for grain protein and diastatic power level coincided with the locations of known function genes. Coincident QTL for a number of malting-quahty traits on chromosome 7 suggests either the presence of a multi-locus cluster of genes controlling components of malting quality or a regulatory gene or genes controlling the cascade of enzymatic processes that function during the malting process. Based on these results, simultaneous selection for malting quality and cold tolerance should be possible in this genetic background.

A high efficiency of Hordeum bulbosum-mediated haploid production in barley has been achieved using a floret culture technique in which florets pollinated with Hordeum bulbosum are cultured on modified N6 media containing 0.5 mg/l kinetin and 1.2 mg/l2,4-D. Cultures were maintained at 25 °C with a 16 h photoperiod for 9 days before embryo rescue. In a comparison of haploid production efficiency using five F1 hybrids from winter x winter and winter x spring barley crosses, 41.6 haploid plants/100 florets pollinated were produced using floret culture. Using detached tiller culture, 13.5 haploid plants/100 florets pollinated were produced. Higher efficiencies achieved with floret culture are attributed to the formation of larger, differentiated embryos. Such embryos lead to higher frequencies of plant regeneration. The F1 from a winter x winter cross was inferior in haploid production compared to F1s from winter x spring crosses. No genotype x technique interaction was observed.

The use of Hordeum bulbosum L.‐mediated haploid production in barley (Hordeum vulgare L.) germplasm enhancement, gene mapping, and marker‐assisted selection is limited by low efficiencies of haploid production with certain barley genotypes. The primary objective of this study was to assess genotypic variation for haploid production efficiency in an array of 10 winter and facultative barley cultivars of diverse geographic origin. Another objective was to compare in vitro floret and tiller culture as aids to haploid production by the bulbosum method. There was significant genotypic variation for haploid production efficiency (HPE), computed as the number of haploid plants regenerated/100 florets pollinated with both techniques. The highest HPE (48) was achieved with ‘Schuyler’ using floret culture, a technique in which barley florets pollinated with H. bulbosum L. are cultured on modified N6 media containing 0.5 mg L−1 kinetin and 1.2 mg 2,4‐D L−1. Mean HPEs achieved with floret and tiller culture were 35 and 15, respectively. Cultivars exhibited differential HPE response. Of the components of haploid production efficiency (seeds/100 florets, embryos/100 seeds, and plants/100 embryos), a significant genotype ✕ culture technique interaction was found only for embryos/100 seeds. The use of floret culture as an aid to H. bulbosum L.‐mediated haploid production should facilitate barley germplasm enhancement, mapping, and selection efforts requiring routine doubled haploid synthesis from genetically broadbased germplasm arrays.