Teulat et al. (1998) located QTL for osmotic adjustment using RILs derived from a cross between drought tolerant and susceptible genotypes. Plants were grown under both water-stress and well- watered conditions, and measured for various traits correlated with osmotic adjustment. They found two QTL regions on chromosome 7H, one that was significantly associated with relative water content (RWC) and another associated with both RWC and leaf osmotic potential.

Qi et al. (1998a) developed an AFLP map for an L94/Vada recombinant inbred population, containing 561 AFLP markers, three morphological markers, one disease resistance gene and one STS marker. The AFLP markers tended to cluster around the centromeres, but there were only three marker gaps in the map larger than 20 cM. The chromosome 7H map has 96 markers with one gap greater than 20 cM. They then used this map to locate QTL involved in partial resistance to leaf rust (Qi et al. 1998b), by measuring latent period and area under the disease progress curve (AUDPC). Six QTL were identified, including one minor QTL on chromosome 7H. The locus Rphq1 affected both resistance at the seedling stage and AUDPC. In contrast to other QTL they located, Rphq1 lengthened the latent period in seedlings but not in adult plants.

AFLP markers also were used to map sodium azide-induced mutations reducing phytic acid content of barley grain. Larson et al. (1998) found that lpa2-1, which lowers phytic acid phosphorous and increases inorganic phosphorus content compared to normal kernels, was linked to AFLP markers that map to chromosome 7H. Comparative mapping of lpa2 in maize indicates that the maize and barley genes may be orthologous. Transfer of these mutants into breeding programs should improve the nutritional quality of feed barley.

Han et al (1998) compared rice-barley synteny for two chromosomal regions, including the 7H centromeric region. This region between Brz and Amy2 contains two putative overlapping QTL that affect multiple malting quality traits. The central portion of the chromosome segment shows strong synteny to rice chromosome 8, while the outer segments are syntenic to rice chromosomes 1, 3, 6, and 10. Elucidating these syntenic relationships will provide additional markers for fine mapping of specific chromosomal regions and aid in gene isolation. The authors discuss possible evolutionary mechanisms that could result in the observed synteny.

Seah et al. (1998) amplified resistance gene analogs using primers derived from conserved sequences from the Cre3 locus of wheat. Three sequences amplified in barley were cloned and sequenced, and two were selected for mapping. These clones hybridized to multiple sequences. One band mapped to the short arm of 7H, near Rpg1 and two mapped near the end of the long arm of chromosome 7H. Mena et al. (1998) examined regulation of transcription of prolamine protein genes in barley. They used a maize prolamine-box binding factor (Pbf) cDNA clone to isolate homologous sequences from a barley cDNA library and then tested the selected sequences. They determined that the gene's product binds to the promoter of the Hor2 gene and transactivates transcription of this prolamine gene in barley endosperm. Southern analysis of wheat-barley addition lines indicated that the barley Pbf is located on chromosome 7H.

Taketa et al. (1998) identified QTL associated with crossability of barley with wheat by crossing wheat with doubled haploid lines used to develop the Steptoe/Morex linkage map. Four QTL were located, including one on the short arm of chromosome 7H, contributed by Morex. Alvarez et al. (1998) used wheat-Hordeum chilense addition lines to locate a gene(s) for greater carotenoid pigment to chromosome 7H^ch. Comparative mapping indicated that this may be a common location for carotenoid pigment genes in grasses.

References:

Alvarez, J.B., L.M. Martin, and A. Martin. 1998. Chromosomal localization of genes for carotenoid pigments using addition lines of Hordeum chilense in wheat. Plant Breeding 117:287-289.

Han, F., A. Kleinhofs, S.E. Ullrich, A. Kilian, M. Yano, and T. Sasaki. 1998. Synteny with rice: analysis of barley malting quality QTLs and rpg1 chromosome regions. Genome 41:373-380.

Larson, S.R., K.A. Young, A. Cook, T.K. Blake, and V. Raboy. 1998. Linkage mapping of two mutations that reduce phytic acid content of barley grain. Theor. Appl. Genet. 96:141-146.

Mena, M., J. Vicente-Carbajosa, R.J. Schmidt, and P. Carbonero. 1998. An endosperm-specific DOF protein from barley, highly conserved in wheat, binds to and activates transcription from the prolamin-box of a native B- hordein promoter in barley endosperm. Plant J. 16:53-62.

Qi, X., P. Stam and P. Lindhout. 1998a. Use of locus-specific AFLP markers to construct a high-density molecular map in barley. Theor. Appl. Genet. 96:376-384.

Qi, X., R.E. Nicks, P. Stam, and P. Lindhout. 1998b Identification of QTLs for partial resistance to leaf rust (Puccinia hordei) in barley. Theor. Appl. Genet. 96:1205-1215.

Seah, S., K. Sivasithamparam, A. Karakousis, and E.S. Lagudah. 1998. Cloning and characterization of a family of disease resistance gene analogs from wheat and barley. Theor. Appl. Genet. 97:937-945.

Taketa, S., H. Takahashi, and K. Takeda. 1998. Genetic variation in barley of crossability with wheat and its quantitative trait loci analysis. Euphytica 103:187-193.

Teulat, B., D. This, M. Khairallah, C. Borries, C. Ragot, P. Sourdille, P. Leroy, P. Monneveux, and A. Charrier. 1998. Several QTLs involved in osmotic-adjustment trait variation in barley (Hordeum vulgare L.). Theor. Appl. Genet. 96:688-698.