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A doubled haploid population of 120 individuals was produced from the parents Chebec, an Australian 2-row barley of feed quality with resistance to the cereal cyst nematode, and Harrington, a 2-rowed, Canadian variety of premium malting quality. This paper describes 18 field and laboratory experiments conducted with the population and summarises the traits mapped and analysed. The genomic location of 25 traits and genes is described and marker–trait associations for 5 traits (malt extract, diastatic power, resistance to cereal cyst nematode, early flowering, resistance to pre-harvest sprouting) important to Australian efforts to improve malting barley varieties have been used in practical breeding programs. Detailed maps for these populations are shown in this paper, while a consensus map incorporating these maps and further experiments on the populations are described elsewhere in this issue.

Six doubled haploid barley populations (Alexis × Sloop, Chebec × Harrington, Arapiles × Franklin, Patty × Tallon, Tallon × Kaputar, and Sloop × Halcyon) and a recombinant inbred population (WI2875-1 × Alexis) were assessed for response to selected pathotypes of the barley leaf rust pathogen, Puccinia hordei, at the seedling growth stage. Resistance genes were postulated for the parents of each population based on their reaction to selected pathotypes. In most cases, the resistance genes postulated in the cultivars were validated by QTL mapping analyses of the progeny populations. The resistance genes detected and mapped were Rph2, Rph3, Rph4, Rph12, and Rph19. The chromosomal locations of these 5 genes were consistent with previous reports, with Rph2 mapping near to the centromere on the short arm of chromosome 5H, Rph4 mapping to chromosome 1H, Rph12 mapping to the long arm of chromosome 5H, and Rph3 and Rph19 mapping ~30 cM apart on the long arm of chromosome 7H.

Barley stripe rust (BSR), caused by Puccinia striiformis f. sp. hordei, has been a major disease problem to the barley industry worldwide that has not, to date, been detected in Australia. This paper describes the mapping of stripe rust resistance genes in Tallon/Kaputar (TK) and Arapiles/Franklin (AF) populations. The paper also reports on the usefulness of markers associated with alternative sources of resistance previously identified in the varieties Orca and Shyri in the USA. Stripe rust screening was conducted at the adult plant stage in Toluca, Mexico, for 2 years. Two major quantitative trait loci (QTLs) were found on chromosomes 2H and 5H in both populations. One region on chromosome 5H was highly significantly associated with resistance to stripe rust (R2 = 68% and 34% in TK and AF, respectively). The QTL on chromosome 2H accounted for 36% of the variation in TK and 10% of the variation in the AF population. These associations were consistent over both years. Further work will involve screening for additional markers in the target regions to identify polymorphism that can be used to select for multiple resistances in the absence of the pathogen.

A genetic map of barley with 224 AFLP and 39 simple sequence repeat (SSR) markers was constructed using a doubled haploid (DH) mapping population from a cross between the varieties Tallon and Kaputar. Linkage groups were assigned to individual barley chromosomes using the published map locations of the SSR markers as reference points. This genetic map was used to identify markers with linkage to agronomic, disease, and quality traits in barley. The population, which comprised 65 lines, was tested in a range of environments across Australia. Quantitative trait loci (QTLs) analyses were performed using software packages MapMaker, MapManager, and Qgene. Significant associations with markers were found for several traits. Grain yield showed significant association with regions on chromosomes 2H, 3H, and 5H over a range of sites throughout Australia. Regions on chromosomes 2H and 3H explained 30% and 26% of variation in lodging, respectively. Among quality traits, diastatic power was associated with regions on chromosomes 1H, 2H, and 5H (R2 = 37%). Hot water extract was associated with a region on chromosome 6H and a marker not assigned to a chromosome (R2 = 45%). There were also environment-specific QTLs for the traits analysed. The markers identified here present an opportunity for marker assisted selection of lines for these traits in barley breeding programs.

Identification and deployment of disease resistance genes are key objectives of Australian barley breeding programs. Two doubled haploid (DH) populations derived from Tallon × Kaputar (TK) and VB9524 × ND11231 (VN) crosses were used to identify markers for net type net blotch (NTNB) (Pyrenophora teres f. teres). The maps included 263 and 250 markers for TK and VN populations, respectively. The TK population was screened with 5 pathotypes and the VN population with 1 pathotype of NTNB as seedlings in the glasshouse. In addition, the TK population was subjected to natural infection in the field at Hermitage Research Station, Qld. Analyses of the markers were performed using the software packages MapManager and Qgene. One region on chromosome 6H was strongly associated with resistance to NTNB in both populations (R2 = 83% for TK and 66% for VN). In the TK population, 2 more quantitative trait loci (QTLs) were identified on chromosomes 2H and 3H, with R2 values of 30% and 31%, respectively. These associations were consistent over all pathotypes studied during the seedling stage. The same QTL on chromosome 6H was also found to be highly significantly associated (R2 = 65%) with the adult plant (field) response in the TK population. There are several very closely linked markers showing strong associations in these regions. Association of the 4 markers on chromosome 6H QTL with resistance to the NTNB has been validated in 2 other DH populations derived from barley crosses Pompadour × Stirling and WPG8412 × Stirling. These markers present an opportunity for marker assisted selection of lines resistant to NTNB in barley breeding programs.

Identification and deployment of disease resistance genes are key objectives of Australian barley breeding programs. Two doubled haploid (DH) populations derived from Tallon × Kaputar (TK) and VB9524 × ND11231 (VN) crosses were used to identify markers for net type net blotch (NTNB) (Pyrenophora teres f. teres). The maps included 263 and 250 markers for TK and VN populations, respectively. The TK population was screened with 5 pathotypes and the VN population with 1 pathotype of NTNB as seedlings in the glasshouse. In addition, the TK population was subjected to natural infection in the field at Hermitage Research Station, Qld. Analyses of the markers were performed using the software packages MapManager and Qgene. One region on chromosome 6H was strongly associated with resistance to NTNB in both populations (R2 = 83% for TK and 66% for VN). In the TK population, 2 more quantitative trait loci (QTLs) were identified on chromosomes 2H and 3H, with R2 values of 30% and 31%, respectively. These associations were consistent over all pathotypes studied during the seedling stage. The same QTL on chromosome 6H was also found to be highly significantly associated (R2 = 65%) with the adult plant (field) response in the TK population. There are several very closely linked markers showing strong associations in these regions. Association of the 4 markers on chromosome 6H QTL with resistance to the NTNB has been validated in 2 other DH populations derived from barley crosses Pompadour × Stirling and WPG8412 × Stirling. These markers present an opportunity for marker assisted selection of lines resistant to NTNB in barley breeding programs.

A doubled haploid population of 120 individuals was produced from the parents Chebec, an Australian 2-row barley of feed quality with resistance to the cereal cyst nematode, and Harrington, a 2-rowed, Canadian variety of premium malting quality. This paper describes 18 field and laboratory experiments conducted with the population and summarises the traits mapped and analysed. The genomic location of 25 traits and genes is described and marker–trait associations for 5 traits (malt extract, diastatic power, resistance to cereal cyst nematode, early flowering, resistance to pre-harvest sprouting) important to Australian efforts to improve malting barley varieties have been used in practical breeding programs. Detailed maps for these populations are shown in this paper, while a consensus map incorporating these maps and further experiments on the populations are described elsewhere in this issue.

Six doubled haploid barley populations (Alexis × Sloop, Chebec × Harrington, Arapiles × Franklin, Patty × Tallon, Tallon × Kaputar, and Sloop × Halcyon) and a recombinant inbred population (WI2875-1 × Alexis) were assessed for response to selected pathotypes of the barley leaf rust pathogen, Puccinia hordei, at the seedling growth stage. Resistance genes were postulated for the parents of each population based on their reaction to selected pathotypes. In most cases, the resistance genes postulated in the cultivars were validated by QTL mapping analyses of the progeny populations. The resistance genes detected and mapped were Rph2, Rph3, Rph4, Rph12, and Rph19. The chromosomal locations of these 5 genes were consistent with previous reports, with Rph2 mapping near to the centromere on the short arm of chromosome 5H, Rph4 mapping to chromosome 1H, Rph12 mapping to the long arm of chromosome 5H, and Rph3 and Rph19 mapping ~30 cM apart on the long arm of chromosome 7H.

Barley stripe rust (BSR), caused by Puccinia striiformis f. sp. hordei, has been a major disease problem to the barley industry worldwide that has not, to date, been detected in Australia. This paper describes the mapping of stripe rust resistance genes in Tallon/Kaputar (TK) and Arapiles/Franklin (AF) populations. The paper also reports on the usefulness of markers associated with alternative sources of resistance previously identified in the varieties Orca and Shyri in the USA. Stripe rust screening was conducted at the adult plant stage in Toluca, Mexico, for 2 years. Two major quantitative trait loci (QTLs) were found on chromosomes 2H and 5H in both populations. One region on chromosome 5H was highly significantly associated with resistance to stripe rust (R2 = 68% and 34% in TK and AF, respectively). The QTL on chromosome 2H accounted for 36% of the variation in TK and 10% of the variation in the AF population. These associations were consistent over both years. Further work will involve screening for additional markers in the target regions to identify polymorphism that can be used to select for multiple resistances in the absence of the pathogen.

A genetic map of barley with 224 AFLP and 39 simple sequence repeat (SSR) markers was constructed using a doubled haploid (DH) mapping population from a cross between the varieties Tallon and Kaputar. Linkage groups were assigned to individual barley chromosomes using the published map locations of the SSR markers as reference points. This genetic map was used to identify markers with linkage to agronomic, disease, and quality traits in barley. The population, which comprised 65 lines, was tested in a range of environments across Australia. Quantitative trait loci (QTLs) analyses were performed using software packages MapMaker, MapManager, and Qgene. Significant associations with markers were found for several traits. Grain yield showed significant association with regions on chromosomes 2H, 3H, and 5H over a range of sites throughout Australia. Regions on chromosomes 2H and 3H explained 30% and 26% of variation in lodging, respectively. Among quality traits, diastatic power was associated with regions on chromosomes 1H, 2H, and 5H (R2 = 37%). Hot water extract was associated with a region on chromosome 6H and a marker not assigned to a chromosome (R2 = 45%). There were also environment-specific QTLs for the traits analysed. The markers identified here present an opportunity for marker assisted selection of lines for these traits in barley breeding programs.