A high-density genetic map was developed from an F1-derived doubled haploid population generated from a cross between cultivated barley (Hordeum vulgare) and the subspecies H. vulgare ssp. spontaneum. The map comprises 1,000 loci, amplified using 536 SSR (558 loci) and 442 DArT markers. Of the SSRs, 149 markers (153 loci) were derived from barley ESTs, and 7 from wheat ESTs. A high level of polymorphism (∼70%) was observed, which facilitated the mapping of 197 SSRs for which genetic assignments had not been previously reported. Comparison with a published composite map showed a high level of co-linearity and telomeric coverage on all seven chromosomes. This map provides access to previously unmapped SSRs, improved genome coverage due to the integration of DArT and EST-SSRs and overcomes locus order issues of composite maps constructed from the alignment of several genetic maps.

Selection for malting quality traits is a major breeding objective for barley breeding programs. With molecular markers linked to loci affecting these traits, this selection can be undertaken at an earlier stage of the breeding program than is possible using conventional tests. Quantitative trait loci (QTLs) associated with malting quality traits were mapped in 2 populations derived from parents with elite malting quality. Progeny from an Arapiles/Franklin population grown in 4 environments and an Alexis/Sloop population grown in 5 environments were tested for grain protein percentage, alpha-amylase activity, diastatic power, hot water extract, wort viscosity, wort beta-glucan, beta-glucanase, and free alpha-amino acids. QTL analysis was performed using a one-stage approach, which allowed for modelling of spatial variation in the field, and in each phase of the malting quality analysis in the laboratory. QTLs for malting quality traits were detected on all chromosomes and for both populations. Few of these QTLs were significant in all of the environments, indicating that QTL x environment interactions were important. There were many coincident QTLs for traits that are expected to be related such as diastatic power and alpha-amylase activity, wort beta-glucan and wort viscosity and for some traits that are not expected to be related such as hot water extract and malt viscosity.

Flour yield quantitative trait loci (QTLs) were identified in 3 Australian doubled haploid populations, Sunco × Tasman, CD87 × Katepwa, and Cranbrook × Halberd. Trial data from 3 to 4 sites or years were available for each population. QTLs were identified on chromosomes 2BS, 4B, 5AL, and 6BL in the Sunco × Tasman population, on chromosomes 4B, 5AS, and 6DL in the CD87 × Katepwa population, and on chromosomes 4DS, 5DS, and 7AS in the Cranbrook × Halberd population. In the Sunco × Tasman cross the highest genetic variance was detected with the QTL on chromosome 2B (31.3%), in the CD87 × Katepwa cross with the QTL on chromosome 4B (23.8%), and in the Cranbrook × Halberd cross with the QTL on chromosome 5D (18%). Only one QTL occurred in a similar location in more than one population, indicating the complexity of the flour yield character across different backgrounds.

Three Australian doubled haploid populations were used to illustrate the importance of map curation in order to improve the quality of linkage maps and quantative trait locus (QTL) detection. The maps were refined and improved by re-examining the order of markers, inspection of the genetic maps in relation to a consensus map, editing the marker data for double crossovers, and determining estimated recombination fractions for all pairs of markers. The re-ordering of markers and replacing genotypes at double crossovers with missing values resulted in an overall decrease in the length of the maps. Fewer apparent genotyping errors, associated with the presence of double recombinants, were identified with restriction fragment length polymorphisms (RFLPs) than with other types of markers used in this study. The complications that translocations may cause in the ordering of markers and subsequent QTL analysis were investigated. QTL analysis using both the original and revised maps indicated that QTL peaks were more sharply located or had improved log-likelihood (LOD) scores in the revised maps. An accurate indication of the QTL peak and a significant LOD score are both essential for the identification of markers suitable for marker-assisted selection. Recommendations are provided for the improvement of the quality of linkage maps.

A high density genetic map comprising 246 SSR and 184 unique DArT loci was constructed using an F1- derived DH population developed from a cross between cultivated barley (H. vulgare, variety Barque) and the closely related species, H. spontaneum (accession CPI 71284-48). The parents of this cross revealed a high (68 per cent) level of polymorphism which facilitated the mapping of previously unmapped markers and an unprecedented level of genetic saturation. Comparisons with published maps showed a high level of co-linearity, although some discrepancies in loci order exist between closely linked markers. This map provides access to previously unmapped SSRs, improved genome coverage due to the integration of DArT and SSR markers and overcomes loci order issues of consensus maps constructed from the alignment of several genetic maps. In addition, the use of H. spontaneum in the cross will aid the introgression of novel traits into adapted barley germplasm.

In order to identify quantitative trait loci (QTLs) controlling grain yield, average grain weight and grain plumpness, the progeny of the mapping population VB9104 x Dash and their parents were grown at three locations (Esperance 2001, Kendenup 2001 and Kendenup 2002) in single replicate trials. QTLs for grain yield, average grain weight and grain plumpness were generally located on chromosome 5H and to a lesser extent on chromosome 2H. Numerous QTLs were common to several locations. The marker Bmag0337 on chromosome 5H was highly associated with grain yield and average grain weight. The positive alleles for grain weight and grain plumpness were from VB9104 and Dash, respectively.

A new approach for multi-environment quantitative trait locus (QTL) analysis based on an appropriate genetic model is presented. To accommodate a multi-environment analysis, the size of a QTL effect is assumed to be a random effect. The approach results in a multiplicative mixed model for QTL × environment interaction of the factor analytic type. The full genetic model may also include a factor analytic model for the residual genotype × environment interaction, whereas the environmental model for the non-genetic variation involves local, global, and extraneous variation. The approach is used to determine QTLs for yield in the Arapiles × Franklin doubled haploid population of the National Barley Molecular Marker Program. Analysis leads to the determination of 8 QTLs. Many of these QTLs are associated with other traits.

The barley mapping population Mundah × Keel was devised to characterise and map chromosome regions associated with improved growth and grain yield on sandy soils of low fertility. A low level of polymorphism between the parents proved problematic for the construction of a detailed linkage map of this population. Despite this, significant quantitative trait loci (QTLs) for specific traits were detected, providing an insight into the probable chromosome regions associated with sand adaptation. In addition, this population is being employed to identify loci associated with the expression of traits for moisture stress and frost tolerance, and resistance to spot form of net blotch and leaf scald.

A map for the barley doubled haploid population Amagi Nijo × WI2585 was constructed to examine manganese efficiency derived from Amagi Nijo. Manganese efficiency conferred by the previously identified locus Mel1 was validated. No other loci contributing to manganese efficiency were identified, possibly because of poor maker coverage in some regions. The map was additionally used to look for loci contributing to some aspects of malting quality. A locus on 2HL was found to be associated with malt extract, and 2 loci on 4HL and 5H, respectively, were found to be associated with diastatic power.

This paper discusses the analysis of quantitative trait loci (QTLs) using molecular markers from a doubled haploid wheat mapping population arising from the Cranbrook Halberd cross. Two field trials are used to provide phenotypic information on the trait of interest, which is grain percentage protein. Methods for QTL analysis are reviewed together with methods for the analysis of field trials. The aim of the paper is to examine different approaches for QTL analysis, namely the conventional approach available in standard software, which ignores field variation, a 2-stage approach that provides adjusted phenotypic effects for a subsequent QTL analysis, and a joint marker and spatial analysis. The major effect, however, is the maturity class of the doubled haploid lines. Maturity and percent protein appear highly correlated genetically so QTL analysis shows marked changes if maturity is included as a covariate. More subtle changes occur due to field variation but this may not be the standard situation.