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.

Quantitative trait locus (QTL) main effects and QTL by environment (QTL × E) interactions for seven agronomic traits (grain yield, days to heading, days to maturity, plant height, lodging severity, kernel weight, and test weight) were investigated in a two-row barley (Hordeura vulgare L.) cross, Harrington/TR306. A 127-point base map was constructed from markers (mostly RFLP) scored in 146 random double-haploid (DH) lines from the Harrington/TR306 cross. Field experiments involving the two parents and 145 random DH lines were grown in 1992 and/or 1993 at 17 locations in North America. Analysis of QTL was based on simple and composite interval mapping. Primary QTL were declared at positions where both methods gave evidence for QTL. The number of primary QTL ranged from three to six per trait, collectively explaining 34 to 52% of the genetic variance. None of these primary QTL showed major effects, but many showed effects that were consistent across environments. The addition of secondary QTL gave models that explained 39 to 80% of the genetic variance. The QTL were dispersed throughout the barley genome and some were detected in regions where QTL have been found in previous studies. Eight chromosome regions contained pleiotropic loci and/or linked clusters of loci that affected multiple traits. One region on chromosome 7 affected all traits except days to heading. This study was an intensive effort to evaluate QTL in a narrow-base population grown in a large set of environments. The results reveal the types and distributions of QTL effects manipulated by plant breeders and provide opportunities for future testing of marker-assisted selection. M OLECULAR MAPS of plant genomes, used in conjunction with phenotypic measurements, can provide information about chromosome regions that affect quantitative traits. Although knowing whether such regions represent individual quantitative trait loci (QTL)

Fusarium head blight (FHB) in barley and wheat, caused by Fusarium graminearum, is a continual problem worldwide. Primarily, FHB reduces yield and quality, and results in the production of the toxin deoxynivalenol (DON), which can affect food safety. Identification of QTLs for FHB severity, DON level and related traits heading-date (HD) and plant-height (HT) with consistent effects across a set of environments, would provide the basis for marker-assisted selection (MAS) and potentially increase the efficiency of selection for resistance. A segregating population of 75 double-haploid lines, developed from the three-way cross Zhedar 2/ND9712//Foster, was used for genome mapping and FHB severity evaluation. A linkage map of 214 RFLP, SSR and AFLP markers was constructed. Phenotypic data were collected in replicated field trials from five environments in two growing seasons. The data were analyzed using MQTL software to detect quantitative trait locus (QTL) x environment (E) interactions. Because of the presence of QTL x E, the MQM procedure in MAPQTL was applied to identify QTLs in single environments. We identified nine QTLs for FHB severity and five for low DON. Many of the disease-related QTLs identified were coincident with FHB QTLs identified in previous studies. Only two of the QTLs identified in this study were consistent across all five environments, and both were Zhedar 2 specific. Five of the FHB QTLs were associated with HD, and two were associated with HT. Regions that appear to be promising candidates for MAS and further genetic analysis include the two FHB QTLs on chromosome 2H and one on 6H, which were also associated with low DON and later heading-date in multiple environments. This study provides a starting point for manipulating Zhedar 2-derived resistance by MAS in barley to develop cultivars that will show effective resistance under disease pressure.

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Russian wheat aphid (RWA, Diuraphis noxia Kurdjumov) infestations reduce grain yield and quality and have caused more than $1 billion in losses for barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) in the western United States since 1986. Our objective was to map quantitative trait loci (QTLs) conferring resistance to RWA feeding damage in the germplasm line STARS‐9301B via polymerase chain reaction–based marker assays of 191 F2–derived F3 families from the cross ‘Morex’/STARS‐9301B. Morex is a susceptible six‐rowed malting barley. STARS‐9301B is a selection from RWA‐resistant Afghanistan introduction PI366450. Replicated seedling reactions to RWA infestations were used to phenotype each family based on a 1 to 9 visual rating of chlorosis. A total of 107 molecular markers was used to construct a linkage map. Quantitative trait loci analysis identified two major QTLs for resistance. The QTL on the short arm of chromosome 1H was associated with B‐hordein and explained 26% of the variation for RWA reaction. A QTL on chromosome 3H associated with EBmac0541 explained 38% of the variation. A minor QTL on chromosome 2H was associated with marker GBM1523 and explained 6% of the variation. A combined analysis indicated that the marker–QTL associations explained 59% of the phenotypic variation for RWA resistance. These markers linked with QTLs will be valuable in breeding for RWA resistance. Pyramiding the genes from STARS‐9301B with genes from other sources will be helpful for long‐term protection against RWA in barley.

Only six haploids in oat (Avena sativa L.) have been previously reported, five of spontaneous origin and one from anther culture. Our objective was to develop more efficient methods for producing oat haploids to use in selecting mutants, recovering aneuploids, and producing doubled‐haploid lines for genetic and breedings tudies. In a series of experiments, pollen from maize (Zea mays L.) was applied to previously emasculated oat florets. Twelve to 15 d later excised ovaries/caryopses, or embryos taken from them, were placed onto an amino acid‐supplemented Murashige and Skoog medium containing 7% sucrose for embryo rescue. Recovered plantlets were potted in soil and grown to maturity. Root tips and meiotic tissues were sampled for cytological analyses. Overall, 14 haploid oat plants were recovered by embryo rescue following application of maize pollen to approximately 3300 emasculated oat florets. Root tip cells in each of the recovered plants had the oat haploid chromosome number of 21. Presumably these oat haploids originated from interspecies hybrid zygote formation followed by elimination of maize chromosomes during initial cell divisions, as has been described in haploid wheat (Triticum aestivum L.) formation in wheat ✕ maize hybridizations. In the initial experiment, which involved combinations of various oat and maize genotypes, each of the four oat haploids recovered was from a different oat cultivar and each involved a different source of maize pollen; thus, indicating that the process is not genotype unique. Meiotic cells of the recovered haploid plants were characterized by aberrant chromosome behavior and numerous micronuclei, as expected in a haploid. Occasional seed were set on haploid plants and both euploid (2n) and aneuploid (2n‐1 and 2n‐2) progeny were obtained. The use of maize pollinations provides a new approach for obtaining haploid oat plants for genetic and breeding studies.

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The semidwarf trait is desired in cereal breeding programs for increased lodging resistance. We characterized 27 brachytic (brh) semidwarf mutants in barley (Hordeum vulgare L.) and located the genes on barley chromosome linkage maps. All brachytic genes were transferred into the two-rowed cultivar Bowman by backcrossing four to seven times and selecting for semidwarf plants. The brachytic lines were evaluated for 10 phenotypic traits: plant height, awn, peduncle, and rachis internode length, leaf length and width, lodging, grain yield, number of kernels per spike, and kernel weight. We intercrossed the lines to determine which mutants were at independent loci and which were alleles at the same locus. F2 populations from 18 brh semidwarfs were constructed for genetic mapping using simple sequence repeat (SSR) markers. The brachytic semidwarf near-isogenic lines were significantly shorter than their normal counterparts and most had lower yields (16/27); shorter awns (26/27), peduncles (26/27), and rachis internodes (24/27); and reduced kernel weight (22/27). Twelve of the lines had shorter penultimate leaves and 15 had reduced lodging. Four lines had increased kernels per spike, while one had fewer kernels per spike. Allelism tests and mapping comparisons indicated that the 27 semidwarfs comprise 18 independent genetic loci. SSR mapping placed these loci in five of the seven barley chromosomes. Knowledge of the effects and locations of these brachytic semidwarf genes will help barley breeders select appropriate lines for barley improvement.