In a mapping population of 68 microspore-derived doubled haploids produced from a F1 hybrid between the strains Blenheim x E224/3 a days to heading QTL was detected on chromosome 7 in the vicinity of the WSP2 protein QTL (Barua et al. 1993). Laurie et al. (1994) mapped 92 loci in a doubled haploid population of 94 plants derived from an Igri x Triumph cross. On this map they located 5 major genes for various traits and eight QTLs for flowering time. A major vernalization locus (probably Sh2), was mapped on the central portion of 7L and a QTL for flowering time on the proximal portion. From a cross between T. Prentice and V. Gold a map with 85 markers covering 1100 cM was produced on a population of 90 bulbosum-derived doubled haploid lines (Kjaer et al. 1995). Segregation distortion was detected for loci located on chromosomes 1, 4 and 7. Initially a QTL for strain diameter was detected on chromosome 7 but it may have been due to a spurious linkage.

One hundred and fifty lines from the Steptoe x Morex population were grown at 3 irrigated and 2 dryland sites and examined for QTLs plus QTL x E interactions for agronomic and malting quality traits (Hayes et al. 1983a). The QTLs located on chromosome 7 include those for plant height, grain protein, diastatic power, malt extract, 2 alpha-amylase QTLs plus a site for QTL x E interactions for yield.

A locus for resistance to barley stripe rust on the M arm of chromosome 7 had a major effect accounting for 57% of the variation in disease severity (Chen et al. 1994). The other major locus was located on chromosome 4.

Hayes et al. (1993b) produced a mapping population of 100 bulbosum-derived doubled haploid lines from a Dickto x Morex cross. In that population 33 markers were mapped with 8 located on chromosome 7. A large QTL for heading date, accounting for 47% of the variability was located on chromosome 7. Major QTLs for cold tolerance factors were located on that chromosome accounting for 37-68% of the variation for three measures of cold tolerance, 47% of the variation for growth habit and 28% of the variation for crown fructun content. When the above map was expanded to 74 markers (Pan et al. 1994) the same interval on chromosome 7 remained as the only region of the genome with significant QTLs for winter survival.

A map with 144 genetic markers was produced on doubled haploid lines derived from a cross between Blenheim and E224/3 (Thomas et al. 1994). QTLs for total grain weight, a weak QTL for decreased % N and a significant hot water extract of a malted grain sample QTL was linked in repulsion to the decreased % N QTL on chromosome 7. In comparison of linkage maps, there was some indication of common loci between European and North American barley germplasm.

Other loci that have recently been assigned to chromosome 7 include the Est9 locus (Yoshima & Konishi, 1994) a mildew resistance gene MITR (Falak, 1994, cited in Jørgensen, 1994) and four new mildew resistance genes from H. spontaneum (Scholfeld et al. 1994 - cited in Jørgensen, 1994) and gene rpg4 providing resistance to pathotype QCC and MCC of barley stem rust caused by P. graminus which was located on the subterminal portion of 7L (Yu Jin and Steffenson, 1994).

Linkage drag from the donor parent has been reported for many mutant genes in barley during backcrossing. Twenty mutant genes on chromosome 7 show an association with R, the rough awn gene (Franckowiak, 1994).

Mohler and Graner (1994) produced 2 doubled haploid populations from reciprocal backcrosses from a Igri x RG127 hybrid to test the differences in recombination between male and female gametophytes. Statistically significant differential recombination was confined to only a small region of the genome and found to be clustered in 3 zones on chromosome 7.

References:

Barua, V.M., K.J. Chalmers, W.T.B. Thomas, C.A. Hackett, V. Lea, P. Jack, B.P. Forster, R.Waugh and W. Powell. 1994. Molecular mapping of genes determining height, time to heading and growth habit in barley (Hordeum vulgare). Genome 36: 1080-1087.

Chen, F.Q., D. Prehn, P.M. Hayes, D. Mulrooney, A. Corey and V. Vivar. 1994. Mapping genes for resistance to barley stripe rust (Puccinia striiformis f. sp. hordei) Theor. Appl. Genet. 88: 215-219.

Franckowiak, J.D. 1994. Notes on linkage drag in Bowman backcross derived lines of spring barley. BGN 24: 63-70.

Hayes, P.M., B.H. Liu, S.J. Knapp, F. Chen, B. Jones, T. Blake, J. Franckowiak, D. Rasmusson, M. Sorrells, S.E. Ullrich, D. Wesenberg, A. Kleinhofs. 1993a. Quantitative trait locus effects and environmental interaction in a sample of North American barley germ plasm. Theor. Appl. Genet. 87: 392-401.

Hayes, P.M., T. Blake, T.H.H. Chen, S. Tragoonrung, F. Chen, A. Pan and B. Lui. 1993b. Quantitative trait loci on barley (Hordeum vulgare L.) chromosome 7 associated with components of winter hardiness. Genome 36, 66-71.

Jørgensen, J.H. 1994. Coordinator's report: Disease and pest resistance genes. BGN 24: 156-157.

Kjaer, B., J. Jensen and H. Giese. 1995. Quantitative trait loci for heading date and straw characters in barley. Genome 38: 1098-1104.

Laurie, D.A., N. Pratchett, J.H. Bezant and J.W. Snape. 1995. RFLP mapping of five major genes and eight quantitative trait loci controlling flowering time in a winter x spring barley (Hordeum vulgare) cross. Genome 38: 575-585.

Mohler, V. and A. Graner. 1994. Analysis of recmbination in male and female gametophytes in barley. BGN 4: 92-93.

Pan, A., P.M. Hayes, F. Chen, T.H.H. Chen, T. Blake, S. Wright, I. Karsai and Z. Bedo. 1994. Genetic analysis of the components of winter hardiness in barley (Hordeum vulgare L.) Theor. Appl. Genet. 89: 900-910.

Thomas, W.T.B., W. Powell, R. Waugh, B.P. Forster, K.J. Chalmers, V.M. Barua, J.S. Swanston, R.P. Ellis, P. Jack, V. Lea. 1994. Quantitative trait loci in a North West European spring barley cross-Blenheim x E224/3. BGN 24: 41-45.

Yoshima, R. and T. Konishi. 1994. Linkage analysis of several isozyme loci in barley. BGN 24: 35-37.

Yue Jin and B.J. Steffenson. 1994. Barley genetic stocks: Reaction to Puccinia graminus f. sp. tritici (ypg4). BGN 24: 169.