Preharvest sprouting (PHS) and dormancy (DOR) can be problems in barley production and end use quality, especially for barley used for seed and malting. Three crosses previously analyzed for DOR inheritance, were reanalyzed for PHS and DOR inheritance using artificial rain to calculate sprout score (SSc) and measure alpha-amylase activity (AA). Germination percentage of untreated grain for DOR was also measured. The crosses are 'Steptoe'/'Morex' (previously published), 'Harrington'/TR306, and 'Triumph'/Morex. Among the three crosses, DOR QTLs were located to six and PHS QTLs to five chromosomes, respectively. Chromosome 6H was never implicated. Previously identified DOR QTLs were confirmed in each cross, and most PHS QTLs coincided with DOR QTLs, but not all. Unique PHS QTLs were identified on chromosomes 1H (AA), 2H (SSc, AA), 3H (SSc, AA), and 7H (SSc, AA) and unique DOR QTLs on 1H, 2H, and 7H. Results indicate that PHS susceptibility and DOR are not always represented by opposite alleles at a locus. Some QTL regions for a given trait are conserved across crosses and some are not. Several QTLs are suitable for marker-assisted selection to balance PHS and DOR in breeding new cultivars.

We isolated the barley stem rust resistance genes Rpg5 and rpg4 by map-based cloning. These genes are colocalized on a 70-kb genomic region that was delimited by recombination. The Rpg5 gene consists of an unusual structure encoding three typical plant disease resistance protein domains: nucleotide-binding site, leucine-rich repeat, and serine threonine protein kinase. The predicted RPG5 protein has two putative transmembrane sites possibly involved in membrane binding. The gene is expressed at low but detectable levels. Posttranscriptional gene silencing using VIGS resulted in a compatible reaction with a normally incompatible stem rust pathogen. Allele sequencing also validated the candidate Rpg5 gene. Allele and recombinant sequencing suggested that the probable rpg4 gene encoded an actin depolymerizing factor-like protein. Involvement of actin depolymerizing factor genes in nonhost resistance has been documented, but discovery of their role in gene-for-gene interaction would be novel and needs to be further substantiated.

Malting and brewing are major uses of barley (Hordeum vulgare L.) worldwide, utilizing 30–40% of the crop each year. A set of complex traits determines the quality of malted barley and its subsequent use for beer. Molecular genetics technology has increased our understanding of genetic control of the many malting and brewing quality traits, most of which are quantitatively inherited. The objective of this study was to further dissect and evaluate a known major malting quality quantitative trait locus (QTL) region of about 28 cM on chromosome 1 (7H). Molecular marker-assisted backcrossing was used to develop 39 isolines originating from a ‘Steptoe’ / ‘Morex’ cross. Morex, a 6–row malting type, was the donor parent and Steptoe, a 6–row feed type, was the recurrent parent. The isolines and parents were grown in four environments, and the grain was micro-malted and analyzed for malting quality traits. The effect of each Morex chromosome segment in the QTL target region was determined by composite interval mapping (CIM) and confirmed and refined by multiple interval mapping (MIM). One QTL was resolved for malt extract content, and two QTLs each were resolved for α-amylase activity, diastatic power, and malt β-glucan content. One additional putative malt extract QTL was detected at the plus border of the target region by CIM, but not confirmed by MIM. All QTLs were resolved to intervals of 2.0 to 6.4 cM by CIM, and to intervals of 2.0 cM or less by MIM. These results should facilitate marker-assisted selection in breeding improved malting barley cultivars.

Malting quality has long been an active objective in barley (Hordeum vulgare L.) breeding programs. However, it is difficult for breeders to manipulate malting-quality traits because of inheritance complexity and difficulty in evaluation of these quantitative traits. Quantitative trait locus (QTL) mapping provides breeders a promising basis with which to manipulate quantitative trait genes. A malting-quality QTL complex, QTL2, was mapped previously to a 30-cM interval in the short-arm telomere region of barley chromosome 4H in a ‘Steptoe’/’Morex’ doubled haploid population by the North American Barley Genome Project, using an interval mapping method with a relatively low-resolution genetic map. The QTL2 complex has moderate effects on several malting-quality traits, including malt extract percentage (ME), α-amylase activity (AA), diastatic power (DP), malt β-glucan content (BG), and seed dormancy, which makes it a promising candidate gene source in malting barley-cultivar development. Fine mapping QTL2 is desirable for precisely studying barley malting-quality trait inheritance and for efficiently manipulating QTL2 in breeding. A reciprocal-substitution mapping method was employed to fine map QTL2. Molecular marker-assisted backcrossing was used to facilitate the generation of isolines. Fourteen different types of ‘Steptoe’ isolines, including regenerated ‘Steptoe’ and 13 different types of ‘Morex’ isolines, including regenerated ‘Morex’, were made within a 41.5-cM interval between MWG634 and BCD265B on chromosome 4H. Duplicates were identified for 12 ‘Steptoe’ and 12 ‘Morex’ isoline types. The isolines together with ‘Steptoe’ and ‘Morex’ were grown variously at three locations in 2 years for a total of five field environments. Four malting-quality traits were measured: ME, DP, AA, and BG. Few significant differences were found between duplicate isolines for these traits. A total of 15 putative QTLs were mapped; three for ME, four for DP, six for AA, and two for BG. Background genotype seemed to make a difference in expression/detection of QTLs. Of the 15 QTLs identified, ten were from the ‘Morex’ and only five from the ‘Steptoe’ background. By combining the results from different years, field environments, and genetic backgrounds and taking into account overlapping QTL segments, six QTLs can be conservatively estimated: two each for ME and AA and one each for DP and BG with chromosome segments ranging from 0.7 cM to 27.9 cM. A segment of 15.8 cM from the telomere (MWG634–CDO669) includes all or a portion of all QTLs identified. Further study and marker-assisted breeding should focus on this 15.8-cM chromosome region.

Moderate seed dormancy is desirable in barley (Hordeum vulgare L.). It is difficult for breeders to manipulate seed dormancy in practical breeding programs because of complex inheritance and large environmental effects. Quantitative trait locus (QTL) mapping opens a way for breeders to manipulate quantitative trait genes. A seed dormancy QTL, SD2, was mapped previously in an 8-cM interval near the chromosome 7 (5H) L telomere from a cross of 'Steptoe' (dormant)/'Morex' (non-dormant) by the North American Barley Genome Project using an interval mapping method and a relatively low-resolution genetic map. SD2 has a moderate dormancy effect, which makes it a promising candidate gene for moderate seed dormancy in barley cultivar development. The fine mapping of SD2 is required for efficient manipulation of SD2 in breeding and would facilitate the study of dormancy in barley. Ten different Morex isolines were generated, including regenerated Morex, of which nine lines had duplicates. The isolines together with Steptoe and Morex were grown in growth room and field environments for 2 years (2000 and 2001). In the growth room, relatively low growing temperatures (25 °C day/15 °C night) were employed to promote seed dormancy development. Seed germination percentage, determined at different post-harvest after-ripening periods, was used to measure seed dormancy. Fine mapping using the substitution mapping method based on differences among isolines resolved the SD2 QTL into an 0.8-cM interval between molecular markers MWG851D and MWG851B near the chromosome 7 (5H) L telomere. Relatively low temperatures (≤25 °C) during seed development promoted the expression of the SD2 dormancy QTL. The chromosome region above the MWG851D-MWG851B interval might play a role in reducing barley seed dormancy during after-ripening.

β‐Amylase (BA) is one of the starch‐degrading enzymes active in germinating barley (Hordeum vulgare L.). Unlike α‐amylase (AA), it is not synthesized de novo at the onset of germination, but accumulates during seed development. BA activity is an important malting quality parameter and is a major contributor, along with AA, to diastatic power (DP). The objectives of this study were to (i) measure and map BA activity in three crosses of North American barleys, (ii) compare quantitative trait loci (QTLs) for BA among various crosses, and (iii) determine the relationship between BA and previously mapped DP QTLs. Comparative mapping was done by means of a consensus map with common markers from F1 doubled haploid mapping populations from the crosses of ‘Steptoe’ × ‘Morex’ (S/M), ‘Harrington’ × TR306 (H/T), and Harrington × Morex (H/M). BA activity analyses were performed with field‐grown seed from the three mapping populations and parents. Relatively normal frequency distributions for enzyme activity were obtained from each of the mapping populations. QTLs for BA were identified in all three crosses and on all seven chromosomes. Seven QTLs were located in S/M, the most genetically diverse cross, while only three each were found in H/T and H/M. As expected, BA QTLs were almost always found in conjunction with previously identified DP QTLs. A survey of QTL literature of populations of diverse germplasm showed many QTLs for BA and DP in common with those identified herein and some unique QTLs as well. The results of this study suggest the benefits of identifying markers closely associated with major BA QTLs are to allow for further molecular studies and for marker assisted selection of this trait.

Acid detergent fibre (ADF) in cultivated barley (Hordeum vulgare vulgare L.) grain, a major indicator of digestibility, negatively affects feed quality, especially of non-ruminant livestock and poultry. Genetic studies of barley grain ADF content have been very limited. The objectives of this study were to map quantitative trait loci (QTLs) affecting ADF content to a molecular marker linkage map in barley, and to determine interactions among the QTLs identified. A population of 150 doubled haploid lines (DHLs) derived from a cross of 'Steptoe'/'Morex' was used for mapping. A total of five QTLs were identified; three with relatively large effects mapping adjacent to one another on chromosome 2H and one each on chromosomes 4H and 1H (5). The five QTLs explained 64.5% of total variation. Steptoe contributed high ADF alleles at all QTLs identified. In order to confirm that the three adjacent QTLs on chromosome 2H are distinct genetic units, three DHLs representing each QTL were selected for backcrossing to Morex. Analysis of F2 ADF data from these three crosses showed that the three QTLs are distinct heritable genetic units. Additivity among the three major QTLs on chromosome 2H and the QTL on chromosome 1H (5) were observed.

Stem rust caused by Puccinia graminis f. sp. tritici was among the most devastating diseases of barley in the northern Great Plains of the U.S. and Canada before the deployment of the stem rust-resistance gene Rpg1 in 1942. Since then, Rpg1 has provided durable protection against stem rust losses in widely grown barley cultivars (cvs.). Extensive efforts to clone Rpg1 by synteny with rice provided excellent flanking markers but failed to yield the gene because it does not seem to exist in rice. Here we report the map-based cloning and characterization of Rpg1. A high-resolution genetic map constructed with 8,518 gametes and a 330-kb bacterial artificial chromosome contig physical map positioned the gene between two crossovers ≈0.21 centimorgan and 110 kb apart. The region including Rpg1 was searched for potential candidate genes by sequencing low-copy probes. Two receptor kinase-like genes were identified. The candidate gene alleles were sequenced from resistant and susceptible cvs. Only one of the candidate genes showed a pattern of apparently functional gene structure in the resistant cvs. and defective gene structure in the susceptible cvs. identifying it as the Rpg1 gene. Rpg1 encodes a receptor kinase-like protein with two tandem protein kinase domains, a novel structure for a plant disease-resistance gene. Thus, it may represent a new class of plant resistance genes.

The barley stem rust resistance gene rpg4 was physically and genetically localized on two overlapping BAC clones covering an estimated 300-kb region of the long arm of barley chromosome 7(5H). Initially, our target was mapped within a 6.0-cM region between the previously described flanking markers MWG740 and ABG391. This region was then saturated by integrating new markers from several existing barley and rice maps and by using BAC libraries of barley cv. Morex and rice cv. Nipponbare. Physical/genetic distances in the vicinity of rpg4 were found to be 1.0 Mb/cM, which is lower than the average for barley (4 Mb/cM) and lower than that determined by translocation breakpoint mapping (1.8 Mb/cM). Synteny at high resolution levels has been established between the region of barley chromosome 7(5H) containing the rpg4 locus and the subtelomeric region of rice chromosome 3 between markers S16474 and E10757. This 1.7-cM segment of the rice genome was covered by two overlapping BAC clones, about 250 kb of total length. In barley the markers S16474 and E10757 genetically delimit rpg4, lying 0.6 cM distal and 0.4 cM proximal to the locus, respectively.

Genetic control of seed dormancy in barley (Hordeum vulgare L.) has been studied recently by means of quantitative trait loci (QTL) mapping. Four QTL, designated SDI to SD4, were found associated with about 75% of the phenotypic variation for dormancy in ‘Steptoe’/ ‘Morex’ crosses. The objective of this study was to investigate the individual effects of seed dormancy(SD) QTL and the nature of their epistatic interactions on dormancy during seed development and after ripening. Six F1‐derived doubled haploid lines from Steptoe/Morex crosses, selected on the basis of the flanking marker alleles for the four SD QTL, and the two parents were grown under greenhouse conditions. The same lines and four additional doubled haploid lines from the same cross were also grown in a field experiment. Genotypic dependence of onset, maintenance, and release of dormancy was studied. To assess dormancy, germination tests of excised embryos from fresh and artificially dried seed were conducted during seed development. All genotypes showed a similar pattern of germination of excised embryos. Since no differences in the time of dormancy inception were found, this phenomenon does not seem to be controlled by the SD QTL. Rather, the SD QTL were involved in the release of dormancy at the end of the development process and during after ripening. The presence of the Steptoe allele at SD1 on chromosome 7 (5H) kept precocious germination to a minimum until the end of the seed development process. On the basis of the dormancy profiles at after ripening, genotypes could be classified as affecting early, intermediate, and late dormancy release. These groups were genotypically dependent. A model for allele interactions among the SD QTL was developed.

In the course of map-based cloning of the barley stem rust resistance gene Rpg1, we identified a rice bacterial artificial chromosome (BAC) containing the Rpg1 flanking markers. Based on the excellent gene order colinearity between barley and rice in this region, we expected that this rice BAC would contain the barley Rpg1 homologue. In order to identify the putative rice homologue, we sequenced ca. 35 kb of the rice BAC at random and then an additional 33 kb of contiguous sequence between the two most closely spaced Rpg1 flanking markers. Sequence analysis revealed a total of 15 putative genes, 5 within the 33-kb contiguous region. A rice Rpg1 homologue was not identified, although a gene encoding a hypothetical polypeptide with similarity to a membrane protein could not be eliminated as a candidate. Surprisingly, four of the genes identified in the 33-kb contiguous rice sequence showed a high degree of similarity with genes on Arabidopsis chromosome 4. The genome regions harboring these genes showed some relatedness, but many rearrangements were also evident. These data suggest that some genes have remained linked even over the long evolutionary separation of Arabidopsis and rice, as has also been reported for mammals and invertebrates.

A major barley seed dormancy locus, SD1, was previously identified along with three others by quantitative trait locus (QTL) analysis in a Steptoe×Morex mapping population. Located in the centromere region of barley chromosome 7 (5H), SD1 shows the largest and most consistent effect on dormancy. Steptoe contributes the dormancy allele at SD1. The objective of this study was to determine the inheritance of and a more precise map location for SD1. A segregating population was designed and generated by marker assisted mating in which only SD1 segregated. The segregation ratio suggested a single Mendelian gene in which the dormancy allele is dominant to the non-dormancy allele at SD1. In addition, near isogenic lines (NIL) for the SD1 chromosome region were generated by molecular marker assisted backcrossing. Statistical analysis of germination percentages of these NIL revealed that there may be a gene cluster of at least three genes in the SD1 locus region. The dormancy locus, presumably SD1 or a part of the SD1 complex, was resolved into a ≈4.4 cM region.

The barley (Hordeum vulgare L.) chromosome 1 centromere region contains two adjacent overlapping quantitative trait loci (QTLs) for malting quality traits, and the chromosome 7L subtelomere region contains the stem rust (causal agent Puccinia graminis f.sp. tritici) resistance gene rpg4. To facilitate the saturation mapping of these two target regions, a synteny-based approach was employed. Syntenic relationships between the barley target regions and the rice (Oryza sativa) genome were established through comparative mapping. The barley chromosome 1 centromere region was found to be syntenic with rice chromosome 8 and parts of rice chromosomes 3 and 10. A 6- to 15-fold difference in genetic distance between barley and rice in the syntenic region was observed, owing to the apparent suppressed recombination in the barley chromosome 1 centromere region. Barley chromosome 7L was found to be syntenic with rice chromosome 3. The establishment of synteny with rice in the two target regions allows well-established and characterized rice resources to be utilized in fine mapping and map-based cloning studies.Key words: genome synteny, quantitative trait loci, QTL, disease resistance gene, Triticeae.

Selection for malting quality in breeding programs by micromalting and micromashing is time-consuming, and resource-intensive. More efficient and feasible approaches for identifying genotypes with good malting quality would be highly desirable. With the advent of molecular markers, it is possible to map and tag the loci affecting malting quality. The objective of this study was to assess the effectiveness of molecular marker assisted selection for malting quality traits. Two major quantitative trait loci (QTL) regions in six-row barley for malt extract percentage, α-amylase activity, diastatic power, and malt β-glucan content on chromosomes 1 (QTL1) and 4 (QTL2) have been previously identified. The flanking markers, Brz and Amy2, and WG622 and BCD402B, for these two major QTL regions were used in marker-assisted selection. Four alternative selection strategies; phenotypic selection, genotypic selection, tandem genotypic and phenotypic selection, and combined phenotypic and genotypic selection, were compared for both single and multiple trait selection in a population consisting of 92 doubled haploid lines derived from ‘Steptoe’ × ‘Morex’ crosses. Marker assisted selection for QTL1 (tandem genotypic and phenotypic selection, and combined phenotypic and genotypic selection) was more effective than phenotypic selection, but for QTL2 was not as effective as phenotypic selection due to a lack of QTL2 effects in the selection population. The effectiveness of tandem genotypic and phenotypic selection makes marker assisted selection practical for traits which are extremely difficult or expensive to measure such as most malting quality traits. It can substantially eliminate undesirable genotypes by early genotyping and keeping only desirable genotypes for later phenotypic selection.

Many economically important traits of crop species are complexly inherited quantitative traits (QT). Trait expression tends to be continuous due to control by multiple genes (G), the environment (E), and G x G and G x E interactions. The development of comprehensive genome maps and quantitative trait locus (QTL) analysis procedures allowed the first significant examination of the genetic control of QTs. Malt extract is a good example of a QT in barley. Heretofore, little has been known about the genetic control of malt extract. The objective of this study was to elucidate the genetic characteristics of malt extract primarily from QTL analyses of the Steptoe x Morex cross. QTL analysis of data from the Steptoe x Morex F-1-derived double haploid mapping population has revealed the location of five malt extract QTLs on three of barley's seven chromosomes. Most of the chromosome regions involved also contain QTLs for other related malting quality traits including alpha-amylase activity, diastatic power, barley and malt beta-glucan content, beta-glucanase activity, and/or seed dormancy. The overlapping QTLs indicate either linked genes or pleitropy or both. Analyses also indicated additive and G x E interactions for malt extract. Fine mapping of a critical region of chromosome 1 is in progress to elucidate the overlapping QTL situation among malt extract and the other quality traits listed above. Location of specific genes for malt extract will facilitate more precise breeding for the improvement of this important trait in barley through molecular marker assisted selection.

The barley stem rust resistance genes Rpg1 and rpg4 were mapped in barley on chromosomes 1P and 7M, respectively and the syntenous rice chromosomes identified as 6P and 3P by mapping common probes in barley and rice. Rice yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC) and cosmid clones were used to isolate probes mapping to the barley Rpg1 region. The rice BAC isolated with the pM13 probe was a particularly excellent source of probes. A high-resolution map of the Rpg1 region was established with 1400 gametes yielding a map density of 3.6 markers per 0.1 cM. A detailed physical map was established for the rice BAC fragment containing the Rpg1-flanking markers pM13 and B24. This fragment covers a barley genetic distance of 0.6 cM and a rice DNA physical distance of ca. 70 kb. The distribution of barley cross-overs in relation to the rice DNA physical distances was extremely uneven. The barley genetic distance between the pM13 marker and Rpg1 was 0.1 cM per ca. 55 kb, while on the proximal side it was 0.5 cm per ca. 15 kb. Three probes from the distal end of the pM13 BAC mapped 3.0 cm proximal of Rpg1 and out of synteny with rice. These experiments confirm the validity of using large insert rice clones as probe sources to saturate small barley (and other large genome cereals) genome regions with markers. They also establish a note of caution that even in regions of high microsynteny, there may be small DNA fragments that have transposed and are no longer in syntenous positions.

The NADPH-dependent HC-toxin reductase (HCTR), encoded by Hm1 in maize, inactivates HC-toxin produced by the fungus Cochliobolus carbonum, and thus confers resistance to the pathogen. The fact that C. carbonum only infects maize (Zea mays) and is the only species known to produce HC-toxin raises the question: What are the biological functions of HCTR in other plant species? An HCTR-like enzyme may function to detoxify toxins produced by pathogens which infect other plant species (R. B. Meeley, G. S. Johal, S. E. Briggs, and J. D. Walton, Plant Cell, 4:71-77, 1992). Hm1 homolog in rice (Y. Hihara, M. Umeda, C. Hara, Q. Liu, S. Aotsuka, K. Toriyama, and H. Uchimiya, unpublished) and HCTR activity in barley, wheat, oats and sorghum have been reported (R. B. Meeley and J. D. Walton, Plant Physiol. 97:1080-1086, 1993). To investigate the sequence conservation of Hm1 and HCTR in barley and the possible relationship of barley Hm1 homolog to the known disease resistance genes, we cloned and mapped a barley (Hordeum vulgare) Hm1-like gene. A putative full-length cDNA clone, Bhm1-18, was isolated from a cDNA library consisting of mRNA from young leaves, inflorescences, and immature embryos. This 1,297-bp clone encodes 363 amino acids which show great similarity (81.6%) with the amino acid sequence of HM1 in maize. Two loci were mapped to barley molecular marker linkage maps with Bhm1-18 as the probe; locus A (Bhm1A) on the long arm of chromosome 1, and locus B (Bhm1B) on the short arm of chromosome 1 which is syntenic to maize chromosome 9 containing the Hm2 locus. The Bhm1-18 probe hybridized strongly to a Southern blot of a wide range of grass species, indicating high conservation of HCTR at the DNA sequence level among grasses. The HCTR mRNA was detected in barley roots, leaves, inflorescences, and immature embryos. The conservation of the HCTR sequence, together with its expression in other plant species (R. B. Meeley and J. D. Walton, Plant Physiol. 97:1080-1086, 1993), suggest HCTR plays an important functional role in other plant species.

Current techniques for quantitative trait locus (QTLs) analyses provide only approximate locations of QTLs on chromosomes. Further resolution of identified QTL regions is often required for detailed characterization. An important region containing malting-quality QTLs on barley (Hordeum vulgare L.) chromosome 1 was identified by previous QTL analyses in a Steptoe×Morex cross. This region contains two putative adjacent overlapping QTLs, each of which has effects on malt-extract percentage, α-amylase activity, diastatic power, and malt β-glucan content. All favorable alleles for these traits are attributed to Morex. The objective of the present study was fine structure mapping of this complex QTL region to elucidate whether these two putative overlapping QTLs are really one QTL. Another question was whether the apparently overlapping QTLs are due to the pleiotropic effects of a single gene, or the independent effects of several genes. A high-resolution map in the target region was developed which spans approximately 27 cM. Molecular-marker-assisted backcrossing was employed to create isogenic lines with a Steptoe background differing only in the region containing the QTLs of interest. A total of 32 different recombinants were identified, of which eight most-informative isogenic lines plus one reconstructed Steptoe control were selected for field testing. The additive effects on malt-extract percentage, α-amylase activity, diastatic power, and malt β-glucan content from eight isogenic lines were calculated based on malting data from three locations. By comparing the significant additive effects among isogenic lines carrying different Morex fragments, two QTLs each for malt extract and for α-amylase, and two to three for diastatic power were identified in certain environments and resolved into 1–8-cM genome fragments. There was a significant QTL×environment interaction for diastatic power, and there are indications that epistatic interactions for malt β-glucan content occur between the QTLs on chromosome 1 and QTLs on other chromosomes.

A method for using alkali treated intact plant tissue as a DNA source for the polymerase chain reaction (PCR) was applied to barley. This method saves up to two days and more than USD 50 per 40 samples by eliminating the need for DNA extraction to produce template for PCR. The conditions were optimized for various barley tissues. Fresh leaves, freeze-dried leaves, and anthers worked well as templates while root, embryo, and endosperm tissues did not. The method was shown to work with several genotypes and different primers. The resulting PCR product could be cut with restriction enzyme to produce clear polymorphism without any interference. This method can be a practical breeding tool by providing a fast, inexpensive method for screening large populations.

Seed dormancy is a relatively complex trait in barley (Hordeum vulgare L.). Several dormancy loci were identified previously by quantitative trait locus analysis. Three reciprocal crosses were made in the present study between parents carrying specific dormancy alleles via linked molecular markers to verify individual dormancy locus effects and potential expression. Analyses of F2 progenies revealed that the dormancy allele at the locus flanked by the markers Ale and ABC302 on the long arm of chromosome 7 had a major effect on dormancy, and was at least partly epistatic to the dormancy locus in the ABC309-MWG851 interval near the telomere of the long arm of chromosome 7. In the absence of the dormancy allele in the Ale-ABC302 interval, the allele in the ABC309-MWG851 interval exerted moderate to large effects on dormancy. Cytoplasmic effects on dormancy were also observed. The germination percentages of progeny with relatively high levels of dormancy were more variable than those of non-dormant or less-dormant progeny, apparently due to environmental effects. Removal of the dormancy allele in the Ale-ABC302 interval, or introducing the dormancy allele in the ABC309-MWG851 interval, should suffice for adjusting dormancy levels in breeding programs to suit various production situations and end uses. The verification of dormancy loci via linked molecular markers allows manipulation of these loci in applied breeding programs.