Gene mapping in barley continued at a rapid pace this year. Many additional markers and genes have been placed on chromosome 7H (1) including microsattelites, sequence tagged sites (STSs) and disease resistance genes. Published papers placing genes and markers on chromosome 7H ( 1) are described below. It is likely that some papers were missed. If the authors send reprints to the address above, they will be included in next year's report. Papers and posters on gene mapping, including integration of morphological and molecular marker maps (Kudrna et al. 1996), were presented at the VII International Barley Genetics Symposium (Jul.30-Aug.6, 1996, Saskatoon, Sask.).

Qi et al. (1996) developed an integrated barley linkage map from four published molecular marker maps. The chromosome 7H (1) integrated map contains 176 markers, including one morphological marker nud (naked caryopsis), and two disease resistance genes Rpg1 and Sb1. A cluster of markers was present around the centromere. This map has only two marker gaps, one 10 cM and one 15 cM, compared to 3-8 gaps in the individual maps.

Comparative mapping among cereals continued with Saghai Maroof et al. (1996) comparing the genomes of rice and barley. Two of the 17 syntenous regions detected were between barley chromosome 7H (1) and rice chromosome 6. Almost half (8/18) of the barley chromosome 7H (1) markers mapped to rice chromosome 6, but the other ten mapped to nine different rice chromosomes.

STS-PCR markers have been placed on chromosomes using wheat-barley addition lines (Blake et al. 1996; Erpelding et al. 1996). Nineteen markers were mapped to chromosome 7H (1), including ten derived from RFLPs that mapped to chromosome 7H (1). Primer sequences for these markers are listed in Blake et al. (1996) and clone sequences are available on GrainGenes and through GenBank.

Liu et al. (1996) have developed 45 simple sequence repeat (SSR) or microsattelite markers for barley. They placed 40 SSRs on four existing linkage maps. Six SSRs mapped to chromosome 7H (1), including three that mapped to gaps in the Steptoe/Morex (S/M) map. Primers used to detect these markers are listed in the paper.

Additional molecular marker maps have been developed to identify QTL. Bezant et al. (1996) located eight QTL for flowering time and three for plant height in Blenheim x Kym doubled haploid (DH) progeny. One dwarfing QTL was located on chromosome 7HL (1L). One earliness QTL was located on chromosome 7HS (1S) and two on 7HL (1L). Oziel et al. (1996) located malting quality and winterhardiness QTLs in Dicktoo x Morex DH progeny. Chromosome 7H (1) QTLs were found for diastatic power, alpha amylase, and fine-coarse difference, in the same positions as in the S/M map. A new QTL for grain protein was found on chromosome 7H (1) that was not identified in the S/M map.

Molecular marker maps also were used to locate QTL for resistance to diseases. Steffenson et al. (1996) identified seven QTL for adult plant net blotch resistance, one of which was on chromosome 7HS (1S). The single gene they found for seedling resistance to spot blotch was located on the distal region of 7HS (1S). One of the two QTL for adult plant resistance to spot blotch was located on 7HS (1S) near the seedling resistance gene. Pecchioni et al. (1996) found one major QTL for resistance to leaf stripe (r2=58.5%) that mapped to chromosome 7H (1), tightly linked to the nud locus. One of two minor QTL was located on chromosome 7HL (1L).

Schonfeld et al. (1996) identified three major race-specific powdery mildew resistance genes derived from Hordeum vulgare ssp. spontaneum. Two of these genes were located on chromosome 7H (1) by RFLP analysis. A recessive gene was found on chromosome 7HS (1S) named mlt and a semi-dominant gene was found on 7HL (1L) named Mlf. Closely linked RFLPs were identified for both genes.

Takeda (1996) evaluated 5,560 barley lines for reaction to the insecticide diazinon. A total of 12.7% were sensitive to diazinon. This sensitivity was controlled by a dominant gene named Diz, which was located on chromosome 7H (1) using morphological markers. Gene order was brh1 (br) - Diz - cer-ze (gl5) -nud (n).

References:

Bezant, J., D. Laurie, N. Pratchett, J. Chojecki and M. Kearsey. 1996. Marker regression mapping of QTL controlling flowering time and plant height in a spring barley (Hordeum vulgare L.) cross. Heredity 77:64-73.

Blake, T.K., D. Kadqrzhanova, K.W. Shepherd, A.K.M.R. Islam, P.L. Langridge, C.L. McDonald, J.Erpelding, S. Larson, N.K. Blake and L.E. Talbert. 1996. STS-PCR markers appropriate for wheat-barley introgression. Theor. Appl. Genet. 93:826-832.

Erpelding, J.E., N.K. Blake, T.K. Blake and L.E. Talbert. 1996. Transfer of sequence tagged site PCR markers between wheat and barley. Genome. 39:802-810.

Kudrna, D., A. Kleinhofs, A. Kilian and J. Soule. 1996. Integrating visual markers with the Steptoe x Morex RFLP map. p. 343. V International Oat Conference and VII International Barley Genetics Symposium Proceedings. A.E. Slinkard, J.G. Scoles, and B.G. Rossnagel (eds.). University Extension Press, Univ. Saskatchewan, Saskatoon, Saskatchewan.

Liu, Z.-W., R.M. Biyashev and M.A. Saghai Maroof. 1996. Development of simple sequence repeat DNA markers and their integration into a barley linkage map. Theor. Appl. Genet. 93:869-876.

Oziel, A., P.M. Hayes, F.Q. Chen and B. Jones. 1996. Application of quantitative trait locus mapping to the development of winter-habit malting barley. Plant Breeding 115:43- 51.

Pecchioni, N., P. Faccioli, H. Toubia-Rahme, G. Valè and V. Terzi. 1996. Quantitative resistance to barley leaf stripe (Pyrenophora graminea) is dominated by one major locus. Theor. Appl. Genet. 93:97-101.

Qi, X., P.Stam and P.Lindhout. 1996. Comparisons and integration of four barley genetic maps. Genome 39:379-394.

Saghai Maroof, M.A., G.P. Yang, R.M. Biyashev, P.J. Maughan and Q. Zhang. 1996. Analysis of the barley and rice genomes by comparative RFLP linkage mapping. Theor. Appl. Genet. 92:541-551.

Schönfeld, M., A. Ragni, G. Fischbeck and A. Jahoor. 1996. RFLP mapping of three new loci for resistance to powdery mildew (Erysiphe graminis f. sp. hordei) in barley. Theor. Appl. Genet. 93:48-56.

Steffenson, B.J., P.M. Hayes and A. Kleinhofs. 1996. Genetics of seedling and adult plant resistance to net blotch (Pyrenophora teres f. teres) and spot blotch (Cochliobolus sativus) in barley. Theor. Appl. Genet. 92:552-558.

Takeda, K. 1996. Inheritance of sensitivity to the insecticide diazinon in barley and the geographical distribution of sensitive varieties. Euphytica 89:297-304.